define romantic love essay

• Bipolar Disorder
• Therapy Center
• When To See a Therapist
• Types of Therapy
• Best Online Therapy
• Best Couples Therapy
• Best Family Therapy
• Managing Stress
• Sleep and Dreaming
• Understanding Emotions
• Self-Improvement
• Healthy Relationships
• Student Resources
• Personality Types
• Guided Meditations
• Verywell Mind Insights
• 2023 Verywell Mind 25
• Mental Health in the Classroom
• Editorial Process
• Meet Our Review Board
• Crisis Support

What Is Romantic Love?

Sheri Stritof has written about marriage and relationships for 20+ years. She's the co-author of The Everything Great Marriage Book. 

Carly Snyder, MD is a reproductive and perinatal psychiatrist who combines traditional psychiatry with integrative medicine-based treatments.

Cavan Images / Getty Images

3 Components of Romantic Love

Romantic love vs. other kinds of love, phases of romantic love, romantic love and sexual desire.

Although there isn’t one clear definition, romantic love is most often thought of as a combination of attraction and idealization that can result in (or from) a bonded relationship. Romantic love has inspired artists for centuries and been the subject of countless plays, songs, movies, books, and other creative endeavors.

As anyone who's been in love knows, love is complicated and capable of eliciting strong emotions, from elation to heartbreak. Romantic relationships go through ups and downs—from that initial, intoxicating "honeymoon" phase to a sense of disappointment and, ideally, to a state of acceptance and a desire for permanence. It can be challenging to move through these phases, but the reward is a healthy, long-term relationship .

At a Glance

Romantic love combines intimacy, passion, and commitment and tends to occur in phases. Infatuation is often followed by disillusionment and challenges before a mature type of romantic love takes hold.

According to Sternberg's triangular theory of love , there are three components of love: intimacy, passion, and decision/commitment. These can apply in romantic relationships and other interpersonal relationships.

Intimacy involves the feelings of connection, closeness, and bond that people experience in a romantic relationship. During the early phases of a relationship, this often involves sexual intimacy. As the relationship progresses, emotional intimacy takes on a more important role.

This involves the feelings of physical and romantic attraction that people experience when they are in love.

Commitment involves deciding to stay with your partner. People develop shared goals and decide to work toward them together.

The presence, absence, and combination of these three components make up seven different types of love.

7 Types of Love

• Friendship : Intimacy without passion or commitment
• Infatuation : Passion without intimacy or commitment
• Empty love : Commitment without passion or intimacy
• Romantic love : Passion and intimacy without commitment
• Companionate love : Intimacy and commitment without passion/sexual desire; this could also be called "platonic" love
• Fatuous love : Commitment and passion without intimacy
• Consummate love : Commitment, passion, and intimacy; represents an ideal relationship

Romantic love often progresses through some of Sternberg's types of love in a few predictable stages. A relationship may start out as friendship or infatuation, and then proceed to romantic love and eventually consummate love. Or, it might develop from infatuation to romantic love but then become companionate or empty.

Infatuation

During the infatuation phase, also known as lust, you feel exhilaration, passion, and elation when you and your lover are together. This is what is often referred to as the "honeymoon phase" of a relationship.

Neurochemicals in the brain , such as dopamine and norepinephrine—also known as the "feel-good" chemicals—are released. These chemicals make us giddy, energetic, and euphoric, sometimes leading to decreased appetite and insomnia. You actually can be so "in love" that you can’t eat or sleep. 

The high you feel during the infatuation phase leads you to idealize the other person and want to be with them constantly; you think about them all the time.

Because this person seems perfect during this phase, you are also unable to see their flaws and shortcomings—hence the saying "love is blind." Typically, the infatuation phase lasts for around six months to a year.

Disillusionment

The first sign that the infatuation phase is wearing off is a sense of disillusionment. Reality sets in and you start to notice flaws in your partner. Some of the same traits that you found so attractive at first start to show their downside. For example, someone who seemed confident and decisive at first might now seem rude and close-minded.

Additionally, as the high wears off, you both start to show your true personalities and aren't as forgiving and unselfish as you were when your partner seemed like they could do no wrong.

While at first, you may have gone out of your way to accommodate the other person, you may start to feel like your own needs aren't being met .

As idealization fades, you may find yourself feeling resentful that your partner is no longer causing that wonderfully infatuated feeling anymore. In some cases, serious problems and red flags , like addiction  or abusive tendencies, can reveal themselves, and potentially be dealbreakers.

The relationship now faces a turning point. Getting through this phase requires the ability to compromise, to speak up about your needs and wants, and to learn how to resolve conflict productively.

Rather than trying to change your partner, your focus should be on learning to respect each other. You will discover if, ultimately, you both have the desire to make the relationship work.

Being able to manage the inevitable bumps in the road is a good indicator that the relationship can evolve into something more long-lasting and stable. 

Committing to a person who inspires romantic feelings, and communicating your dreams, desires, and thoughts to one another, can lead to true intimacy and attachment, the next stage of love.

Mature Love

Just because the passion doesn't stay red-hot and unrelenting doesn't mean that love doesn't continue.

Mature love (or consummate love, in Sternberg's theory) is the kind of devotion found in long-term relationships and successful marriages. In mature love, two people are together because they want to be together and not just because they feel an irrational desire or need to be with one another.

Signs of mature love include:

• Emotional support
• Consideration

Cementing this phase is oxytocin , sometimes called "the cuddle hormone," because it compels you and your partner to get close and to bond.

Scientific research suggests that the brain activity of couples in mature relationships is very similar to the brain activity of those newly in love.

Just because you're not pining for the person doesn't mean it's not true love. In fact, mature love is usually deeper and more meaningful (not to mention much more sustainable) than its younger counterpart.

For most couples, sexual desire is an important part of a romantic relationship. Although it is of course possible to have sexual attraction without an emotional bond, and vice versa, romantic love usually includes both. And since the brain responds in similar ways to both, researchers speculate that they reinforce each other.

Evolutionary psychologists suggest that when sexual desire is paired with love, it creates a stronger bond. This keeps couples together, which benefits their children.

What This Means For You

Romantic love may mean different things to different people. What's most important is that you and your partner are on the same page. Shared intimacy and passion can often lead to a strong, shared commitment to another person and to a lasting relationship.

Sternberg RJ.  A triangular theory of love .  Psychol Rev . 1986;93(2):119-135. doi:10.1037/0033-295x.93.2.119

De Boer A, van Buel EM, Ter Horst GJ. Love is more than just a kiss: a neurobiological perspective on love and affection . Neurosci . 2012;201:114-24. doi:10.1016/j.neuroscience.2011.11.017

Schneiderman I, Zagoory-Sharon O, Leckman JF, Feldman R. Oxytocin during the initial stages of romantic attachment: Relations to couples’ interactive reciprocity . Psychoneuroendocrinology. 2012;37(8):1277-1285. doi:10.1016/j.psyneuen.2011.12.021

Cacioppo S, Bianchi‐Demicheli F, Frum C, Pfaus JG, Lewis JW. The common neural bases between sexual desire and love: A multilevel kernel density fMRI analysis . J Sex Med. 2012;9(4):1048-1054. doi:10.1111/j.1743-6109.2012.02651.x

Birnbaum GE, Reis HT. Evolved to be connected: The dynamics of attachment and sex over the course of romantic relationships . Curr Opin Psychol. 2019;25:11-15. doi:10.1016/j.copsyc.2018.02.005

Bode A, Kushnick G. Proximate and ultimate perspectives on romantic love . Front Psychol . 2021;12:573123. doi:10.3389/fpsyg.2021.573123

Gottman J. The 3 phases of love . The Gottman Institute.

By Sheri Stritof Sheri Stritof has written about marriage and relationships for 20+ years. She's the co-author of The Everything Great Marriage Book. 

• Relationships

What Is Romantic Love?

Is it an evolutionary adaptation, a social construct, or something else.

Posted February 9, 2020 | Reviewed by Daniel Lyons M.A.

• Why Relationships Matter
• Find a therapist to strengthen relationships

What is love? The word love has been used synonymously with enjoyment, enthusiasm, attachment , affection, sexual attraction , care, concern, loyalty, devotion, etc.

It's important to distinguish: r omantic love (also known as romance) has a more specific meaning, and refers to “ intense attraction that involves the idealization of the other, within an erotic context, with the expectation of enduring for some time into the future.” 1 In today’s post, I examine four ways of looking at romance.

1. Romantic love as an evolutionary adaptation.

Let me start with one of the less romantic views of romantic love, which suggests love is a product of forces that increase the chances of passing on one’s genes to future generations.

Some readers may be thinking that passing on one’s genes requires sex only, so what’s love got to do with it (as Tina Turner might say)?

To explain, let me first note we often seek romantic partners who have high levels of certain qualities (e.g., health, beauty, wealth). Assuming we succeed in acquiring a partner with those qualities, however, we face two problems.

One, those qualities do not last (e.g., our partners grow old, get ill, lose their high-paying jobs). Second, we may be tempted by individuals with greater positive attributes (e.g., richer, younger, smarter, prettier).

So, what would keep an individual from divorcing or cheating on their significant other? According to the evolutionary psychologist David Buss, the answer is love. 2-4

Love evolved as a solution to what Buss calls the “ problem of commitment .” It is only when we love our partner that we refuse to leave them even if they lose what we value in them (e.g., money, looks, abilities) or if someone “better” comes along .

2. Romantic love as what unites us with our partner.

Switching now to what may be the most romantic view of love, let us talk about soulmates. In Plato’s The Symposium , Aristophanes gives the following famous story as the origins of soulmates:

Aristophanes says human beings were initially round (their sides and backs formed a circle), had four arms and legs, and one head with two faces which looked in opposite directions. As such, humans were very powerful. So Zeus decided to “ cut them in two [so] they will be diminished in strength.” 5

We human beings, as these split bodies, spend our lives seeking our other halves, so we can be whole again. It is this “desire and pursuit of the whole” that we call "love."

The idea of us looking for our other halves—and the idea that like attracts like—makes sense to many people because we often find ourselves attracted to those with whom we share much in common.

Research also supports this view. For instance, a 2006 study, in which participants rated various aspects of a married couple based on pictures of their faces, found “perceived age, attractiveness , and some personality traits [such as extraversion and conscientiousness ] were similar between partners .” 6

3. Romantic love as a blind force.

They say love is blind but is Cupid blind, too? In other words, do we fall in love with random people?

If love is a blind force, then romance might be triggered by chance encounters with random individuals—not by recognition of meeting a potential soulmate.

This view has also received research support. For instance, attraction is influenced by proximity. According to Zajonc’s “ mere repeated exposure ” theory, when we have regular contact with a stimulus, we develop a preference for that object, person, etc. 7 This means we are more likely to feel attracted to—and form a romantic relationship with—our coworkers, classmates, or neighbors than with strangers.

Of course, proximity alone is rarely enough; proximity-based romantic relationships may not survive if missing other important ingredients (e.g., positive emotions ). 8

Nevertheless, evidence showing that our choice of romantic relationships is influenced by proximity may pose a challenge to the more starry-eyed views of romantic love as possible only between soulmates.

4. Romantic love as a sociocultural construct.

Could it be that how we define love says more about our society and culture than it does about some absolute and universal concept of true love? Perhaps.

For instance, intimacy is an important element of romantic love, but what we consider intimate relationships in America arose in the early nineteenth century; they did so in the context of rapid modernization and urbanization, and the separation of the world of home from work. As one author put it: “Individualism and intimacy are the Siamese twins of modernization .” 9

Nonetheless, even if we were to assume the essence of romantic love is universal and refers to the same thing today as it did many years ago, evidence suggests romantic love was often much less important in the past.

Case in point, in ancient Greece, marriage functioned as a means of reproduction and control over the inheritance of property; however, as societies changed over time so did the institution of marriage . Consequently, a new need arose for a type of love capable of bringing two people together in a “monogamous, lifelong, nuclear family-like bond,” a love that could take the place of “work previously done by patriarchal financial arrangements.” Romantic love became important in part because society “created certain specific work for it to do.” 10

See if you spot any similarities in how your family, friends, or strangers celebrate this holiday. Contemplate what these similarities tell you about traditions and societal expectations (wherever you happen to be living in 2020), the significance of romance, what it means to be romantic, and the right way to celebrate love (e.g., with chocolates, cards, flowers). Consider whether it is possible for you to celebrate love differently. What would such a celebration of love look like?

Facebook image: G-Stock Studio/Shutterstock

1. Jankowiak, W. R., & Fischer, E. F. (1992). A cross-cultural perspective on romantic love. Ethnology, 31, 149-155.

2. Buss, D. M. (1988). Love acts: The evolutionary biology of love. In R. J. Sternberg & M. Barnes (Eds.), The psychology of love (pp. 100– 118). Yale University Press.

3. Buss, D. M. (2000). The dangerous passion: Why jealousy is as necessary as love and sex. Free Press.

4. Buss, D. M. (2006). The evolution of love. In R. J. Sternberg & K. Weis (Eds.), The new psychology of love (pp. 65– 86). Yale University Press.

5. Bury, R. G. (1932). The Symposium of Plato . Cambridge University Press.

6. Little, A. C., Burt, D. M., & Perrett, D. I. (2006). Assortative mating for perceived facial personality traits. Personality and Individual Differences, 40, 973-984.

7. Zajonc, R. B. (2001). Mere exposure: A gateway to the subliminal. Current Directions in Psychological Science, 10, 224–228.

8. Gottman, J. M., & Levenson, R. W. (2000). The timing of divorce: predicting when a couple will divorce over a 14-year period. Journal of Marriage and Family, 62, 737–45.

9. Gadlin, H. (1977). Private lives and public order. In G. Levinger & H. L. Raush (Eds.). Close relationships: Perspectives on the meaning of intimacy (pp. 33-72). University of Massachusetts Press.

10. Jenkins, C. (2017). What love is: And what it could be. Basic Books.

Arash Emamzadeh attended the University of British Columbia in Canada, where he studied genetics and psychology. He has also done graduate work in clinical psychology and neuropsychology in U.S.

• Find a Therapist
• Find a Treatment Center
• Find a Psychiatrist
• Find a Support Group
• Find Teletherapy
• United States
• Brooklyn, NY
• Chicago, IL
• Houston, TX
• Los Angeles, CA
• New York, NY
• Portland, OR
• San Diego, CA
• San Francisco, CA
• Seattle, WA
• Washington, DC
• Asperger's
• Bipolar Disorder
• Chronic Pain
• Eating Disorders
• Passive Aggression
• Personality
• Goal Setting
• Positive Psychology
• Stopping Smoking
• Low Sexual Desire
• Child Development
• Therapy Center NEW
• Diagnosis Dictionary
• Types of Therapy

Understanding what emotional intelligence looks like and the steps needed to improve it could light a path to a more emotionally adept world.

• Coronavirus Disease 2019
• Affective Forecasting
• Neuroscience

Before You Write a Love Essay, Read This to Get Examples

The day will come when you can’t escape the fate of all students: You will have to write a what is love essay.

No worries:

Here you’ll find tons of love essay topics and examples. No time to read everything? Scroll down to get a free PDF with original samples.

Definition: Essay on Love

First, let’s define what is love essay?

The most common topics are:

• Definition of love
• What is love?
• Meaning of love

Why limit yourself to these hackneyed, general themes? Below, I’ll show how to make your paper on love original yet relevant to the prompt you get from teachers.

Love Essay Topics: 20 Ideas to Choose for Your Paper

Your essay on love and relationship doesn’t have to be super official and unemotional. It’s ok to share reflections and personal opinions when writing about romance.

Often, students get a general task to write an essay on love. It means they can choose a theme and a title for their paper. If that’s your case,  feel free to try any of these love essay topics:

• Exploring the impact of love on individuals and relationships.
• Love in the digital age: Navigating romance in a tech world.
• Is there any essence and significance in unconditional love?
• Love as a universal language: Connecting hearts across cultures.
• Biochemistry of love: Exploring the process.
• Love vs. passion vs. obsession.
• How love helps cope with heartbreak and grief.
• The art of loving. How we breed intimacy and trust.
• The science behind attraction and attachment.
• How love and relationships shape our identity and help with self-discovery.
• Love and vulnerability: How to embrace emotional openness.
• Romance is more complex than most think: Passion, intimacy, and commitment explained.
• Love as empathy: Building sympathetic connections in a cruel world.
• Evolution of love. How people described it throughout history.
• The role of love in mental and emotional well-being.
• Love as a tool to look and find purpose in life.
• Welcoming diversity in relations through love and acceptance.
• Love vs. friendship: The intersection of platonic and romantic bonds.
• The choices we make and challenges we overcome for those we love.
• Love and forgiveness: How its power heals wounds and strengthens bonds.

Love Essay Examples: Choose Your Sample for Inspiration

Essays about love are usually standard, 5-paragraph papers students write in college:

• One paragraph is for an introduction, with a hook and a thesis statement
• Three are for a body, with arguments or descriptions
• One last passage is for a conclusion, with a thesis restatement and final thoughts

Below are the ready-made samples to consider. They’ll help you see what an essay about love with an introduction, body, and conclusion looks like.

What is love essay: 250 words

Lao Tzu once said, “Being deeply loved by someone gives you strength while loving someone deeply gives you courage.” Indeed, love can transform individuals, relationships, and our world.

A word of immense depth and countless interpretations, love has always fascinated philosophers, poets, and ordinary individuals. This  emotion breaks boundaries and has a super power to change lives. But what is love, actually?

It’s a force we feel in countless ways. It is the warm embrace of a parent, filled with care and unwavering support. It is the gentle touch of a lover, sparking a flame that ignites passion and desire. Love is the kind words of a friend, offering solace and understanding in times of need. It is the selfless acts of compassion and empathy that bind humanity together.

Love is not confined to romantic relationships alone. It is found in the family bonds, the connections we forge with friends, and even the compassion we extend to strangers. Love is a thread that weaves through the fabric of our lives, enriching and nourishing our souls.

However, love is not without its complexities. It can be both euphoric and agonizing, uplifting and devastating. Love requires vulnerability, trust, and the willingness to embrace joy and pain. It is a delicate balance between passion and compassion, independence and interdependence.

Finally, the essence of love may be elusive to define with mere words. It is an experience that surpasses language and logic, encompassing a spectrum of emotions and actions. Love is a profound connection that unites us all, reminding us of our shared humanity and the capacity for boundless compassion.

What is love essay: 500 words

A 500-word essay on why I love you

Trying to encapsulate why I love you in a mere 500 words is impossible. My love for you goes beyond the confines of language, transcending words and dwelling in the realm of emotions, connections, and shared experiences. Nevertheless, I shall endeavor to express the depth and breadth of my affection for you.

First and foremost, I love you for who you are. You possess a unique blend of qualities and characteristics that captivate my heart and mind. Your kindness and compassion touch the lives of those around you, and I am grateful to be the recipient of your unwavering care and understanding. Your intelligence and wit constantly challenge me to grow and learn, stimulating my mind and enriching our conversations. You have a beautiful spirit that radiates warmth and joy, and I am drawn to your vibrant energy.

I love the way you make me feel. When I am with you, I feel a sense of comfort and security that allows me to be my true self. Your presence envelops me in a cocoon of love and acceptance, where I can express my thoughts, fears, and dreams without fear of judgment. Your support and encouragement inspire me to pursue my passions and overcome obstacles. With you by my side, I feel empowered to face the world, knowing I have a partner who believes in me.

I love the memories we have created together. From the laughter-filled moments of shared adventures to the quiet and intimate conversations, every memory is etched in my heart. Whether exploring new places, indulging in our favorite activities, or simply enjoying each other’s company in comfortable silence, each experience reinforces our bond. Our shared memories serve as a foundation for our relationship, a testament to the depth of our connection and the love that binds us.

I love your quirks and imperfections. Your true essence shines through these unique aspects! Your little traits make me smile and remind me of the beautiful individual you are. I love how you wrinkle your nose when you laugh, become lost in thought when reading a book, and even sing off-key in the shower. These imperfections make you human, relatable, and utterly lovable.

I love the future we envision together. We support each other’s goals, cheering one another on as we navigate the path toward our dreams. The thought of building a life together, creating a home filled with love and shared experiences, fills my heart with anticipation and excitement. The future we imagine is one that I am eager to explore with you by my side.

In conclusion, the reasons why I love you are as vast and varied as the universe itself. It is a love that defies logic and surpasses the limitations of language. From the depths of my being, I love you for the person you are, the way you make me feel, the memories we cherish, your quirks and imperfections, and the future we envision together. My love for you is boundless, unconditional, and everlasting.

A 5-paragraph essay about love

I’ve gathered all the samples (and a few bonus ones) in one PDF. It’s free to download. So, you can keep it at hand when the time comes to write a love essay.

Ready to Write Your Essay About Love?

Now that you know the definition of a love essay and have many topic ideas, it’s time to write your A-worthy paper! Here go the steps:

• Check all the examples of what is love essay from this post.
• Choose the topic and angle that fits your prompt best.
• Write your original and inspiring story.

Any questions left? Our writers are all ears. Please don’t hesitate to ask!

• Essay samples
• Essay writing
• Writing tips

Recent Posts

• Writing the “Why Should Abortion Be Made Legal” Essay: Sample and Tips
• 3 Examples of Enduring Issue Essays to Write Yours Like a Pro
• Writing Essay on Friendship: 3 Samples to Get Inspired
• How to Structure a Leadership Essay (Samples to Consider)
• What Is Nursing Essay, and How to Write It Like a Pro

Search form

• Find Stories
• For Journalists

What is love? Stanford researchers and scholars examine matters of the heart

From the fields of science to sociology, politics and philosophy, here is what Stanford research says about love and romance, in the past and present day.  

For centuries, people have tried to understand the behaviors and beliefs associated with falling in love. What explains the wide range of emotions people experience? How have notions of romance evolved over time? As digital media becomes a permanent fixture in people’s lives, how have these technologies changed how people meet?

Examining some of these questions are Stanford scholars.

From the historians who traced today’s ideas of romance to ancient Greek philosophy and Arab lyric poetry, to the social scientists who have examined the consequences of finding love through an algorithm, to the scientists who study the love hormone oxytocin, here is what their research reveals about matters of the heart.

The evolution of romance

How romantic love is understood today has several historical origins, says Robert Pogue Harrison , the Rosina Pierotti Professor in Italian Literature and a scholar of romance studies.

For example, the idea of finding one’s other half dates back to ancient Greek mythology, Harrison said. According to Aristophanes in Plato’s Symposium , humans were once complete, “sphere-like creatures” until the Greek gods cut them in half. Ever since, individuals have sought after their other half.

Here are some of those origin stories, as well as other historical perspectives on love and romance, including what courtship looked like in medieval Germany and in Victorian England, where humor and innuendo broke through the politics of the times.

Stanford scholar examines origins of romance

Professor of Italian literature Robert Pogue Harrison talks about the foundations of romantic love and chivalry in Western civilization.

Medieval songs reflect humor in amorous courtships

Through a new translation of medieval songs, Stanford German studies Professor Kathryn Starkey reveals an unconventional take on romance.  

The aesthetics of sexuality in Victorian novels

In Queen Victoria’s England, novelists lodged erotic innuendo in descriptive passages for characters to express sexual desire.

Getting to the ‘heart’ of the matter

Stanford Professor Haiyan Lee chronicles the Chinese “love revolution” through a study of cultural changes influenced by Western ideals.

Love in the digital age

Where do people find love today? According to recent research by sociologist Michael Rosenfeld , meeting online is now the most popular way to meet a partner. 

“The rise of the smartphone took internet dating off the desktop and put it in everyone’s pocket, all the time,” said Rosenfeld. He found that 39 percent of heterosexual couples met their significant other online, compared to 22 percent in 2009. 

As people increasingly find connections online, their digital interactions can provide insight into people’s preferences in a partner. 

For example, Neil Malhotra , the Edith M. Cornell Professor of Political Economy, analyzed thousands of interactions from an online dating website and found that people seek partners from their own political party and with similar political interests and ideologies. Here is some of that research. 

Online dating is the most popular way couples meet

Matchmaking is now done primarily by algorithms, according to new research from Stanford sociologist Michael Rosenfeld. His new study shows that most heterosexual couples today meet online.

Cupid’s code: Tweaking an algorithm can alter the course of finding love online

A few strategic changes to dating apps could lead to more and better matches, finds Stanford GSB’s Daniela Saban.

Political polarization even extends to romance

New research reveals that political affiliation rivals education level as one of the most important factors in identifying a potential mate.

Turns out that opposites don’t attract after all

A study of “digital footprints” suggests that you’re probably drawn to personalities a lot like yours.

Stanford scholars examine the lies people tell on mobile dating apps

Lies to appear more interesting and dateable are the most common deception among mobile dating app users, a new Stanford study finds.

The science of love

It turns out there might be some scientific proof to the claim that love is blind. According to one Stanford study , love can mask feelings of pain in a similar way to painkillers. Research by scientist Sean Mackey found intense love stimulates the same area of the brain that drugs target to reduce pain. 

“When people are in this passionate, all-consuming phase of love, there are significant alterations in their mood that are impacting their experience of pain,” said Mackey , chief of the Division of Pain Medicine. “We’re beginning to tease apart some of these reward systems in the brain and how they influence pain. These are very deep, old systems in our brain that involve dopamine – a primary neurotransmitter that influences mood, reward and motivation.”  

While love can dull some experiences, it can also heighten other feelings such as sociability. Another Stanford study found that oxytocin, also known as the love hormone because of its association with nurturing behavior, can also make people more sociable. Here is some of that research. 

Looking for love in all the wrong hormones

A study involving prairie vole families challenges previous assumptions about the role of oxytocin in prosocial behavior.

Give your sweetheart mushrooms this Valentine’s Day, says Stanford scientist

A romantic evening of chocolate and wine would not be possible without an assist from fungi, says Stanford biology professor Kabir Peay. In fact, truffles might be the ultimate romantic gift, as they exude pheromones that can attract female mammals.

Love takes up where pain leaves off, brain study shows

Love-induced pain relief was associated with the activation of primitive brain structures that control rewarding experiences.

Come together: How social support aids physical health

A growing body of research suggests that healthy relationships with spouses, peers and friends are vital for not just mental but also physical health.

• Table of Contents
• Random Entry
• Chronological
• Editorial Information
• About the SEP
• Editorial Board
• How to Cite the SEP
• Special Characters
• Advanced Tools
• Support the SEP
• PDFs for SEP Friends
• Make a Donation
• SEPIA for Libraries
• Entry Contents

Bibliography

Academic tools.

• Friends PDF Preview
• Author and Citation Info
• Back to Top

This essay focuses on personal love, or the love of particular persons as such. Part of the philosophical task in understanding personal love is to distinguish the various kinds of personal love. For example, the way in which I love my wife is seemingly very different from the way I love my mother, my child, and my friend. This task has typically proceeded hand-in-hand with philosophical analyses of these kinds of personal love, analyses that in part respond to various puzzles about love. Can love be justified? If so, how? What is the value of personal love? What impact does love have on the autonomy of both the lover and the beloved?

1. Preliminary Distinctions

2. love as union, 3. love as robust concern, 4.1 love as appraisal of value, 4.2 love as bestowal of value, 4.3 an intermediate position, 5.1 love as emotion proper, 5.2 love as emotion complex, 6. the value and justification of love, other internet resources, related entries.

In ordinary conversations, we often say things like the following:

• I love chocolate (or skiing).
• I love doing philosophy (or being a father).
• I love my dog (or cat).
• I love my wife (or mother or child or friend).

However, what is meant by ‘love’ differs from case to case. (1) may be understood as meaning merely that I like this thing or activity very much. In (2) the implication is typically that I find engaging in a certain activity or being a certain kind of person to be a part of my identity and so what makes my life worth living; I might just as well say that I value these. By contrast, (3) and (4) seem to indicate a mode of concern that cannot be neatly assimilated to anything else. Thus, we might understand the sort of love at issue in (4) to be, roughly, a matter of caring about another person as the person she is, for her own sake. (Accordingly, (3) may be understood as a kind of deficient mode of the sort of love we typically reserve for persons.) Philosophical accounts of love have focused primarily on the sort of personal love at issue in (4); such personal love will be the focus here (though see Frankfurt (1999) and Jaworska & Wonderly (2017) for attempts to provide a more general account that applies to non-persons as well).

Even within personal love, philosophers from the ancient Greeks on have traditionally distinguished three notions that can properly be called “love”: eros , agape , and philia . It will be useful to distinguish these three and say something about how contemporary discussions typically blur these distinctions (sometimes intentionally so) or use them for other purposes.

‘ Eros ’ originally meant love in the sense of a kind of passionate desire for an object, typically sexual passion (Liddell et al., 1940). Nygren (1953a,b) describes eros as the “‘love of desire,’ or acquisitive love” and therefore as egocentric (1953b, p. 89). Soble (1989b, 1990) similarly describes eros as “selfish” and as a response to the merits of the beloved—especially the beloved’s goodness or beauty. What is evident in Soble’s description of eros is a shift away from the sexual: to love something in the “erosic” sense (to use the term Soble coins) is to love it in a way that, by being responsive to its merits, is dependent on reasons. Such an understanding of eros is encouraged by Plato’s discussion in the Symposium , in which Socrates understands sexual desire to be a deficient response to physical beauty in particular, a response which ought to be developed into a response to the beauty of a person’s soul and, ultimately, into a response to the form, Beauty.

Soble’s intent in understanding eros to be a reason-dependent sort of love is to articulate a sharp contrast with agape , a sort of love that does not respond to the value of its object. ‘ Agape ’ has come, primarily through the Christian tradition, to mean the sort of love God has for us persons, as well as our love for God and, by extension, of our love for each other—a kind of brotherly love. In the paradigm case of God’s love for us, agape is “spontaneous and unmotivated,” revealing not that we merit that love but that God’s nature is love (Nygren 1953b, p. 85). Rather than responding to antecedent value in its object, agape instead is supposed to create value in its object and therefore to initiate our fellowship with God (pp. 87–88). Consequently, Badhwar (2003, p. 58) characterizes agape as “independent of the loved individual’s fundamental characteristics as the particular person she is”; and Soble (1990, p. 5) infers that agape , in contrast to eros , is therefore not reason dependent but is rationally “incomprehensible,” admitting at best of causal or historical explanations. [ 1 ]

Finally, ‘ philia ’ originally meant a kind of affectionate regard or friendly feeling towards not just one’s friends but also possibly towards family members, business partners, and one’s country at large (Liddell et al., 1940; Cooper, 1977). Like eros , philia is generally (but not universally) understood to be responsive to (good) qualities in one’s beloved. This similarity between eros and philia has led Thomas (1987) to wonder whether the only difference between romantic love and friendship is the sexual involvement of the former—and whether that is adequate to account for the real differences we experience. The distinction between eros and philia becomes harder to draw with Soble’s attempt to diminish the importance of the sexual in eros (1990).

Maintaining the distinctions among eros , agape , and philia becomes even more difficult when faced with contemporary theories of love (including romantic love) and friendship. For, as discussed below, some theories of romantic love understand it along the lines of the agape tradition as creating value in the beloved (cf. Section 4.2 ), and other accounts of romantic love treat sexual activity as merely the expression of what otherwise looks very much like friendship.

Given the focus here on personal love, Christian conceptions of God’s love for persons (and vice versa ) will be omitted, and the distinction between eros and philia will be blurred—as it typically is in contemporary accounts. Instead, the focus here will be on these contemporary understandings of love, including romantic love, understood as an attitude we take towards other persons. [ 2 ]

In providing an account of love, philosophical analyses must be careful to distinguish love from other positive attitudes we take towards persons, such as liking. Intuitively, love differs from such attitudes as liking in terms of its “depth,” and the problem is to elucidate the kind of “depth” we intuitively find love to have. Some analyses do this in part by providing thin conceptions of what liking amounts to. Thus, Singer (1991) and Brown (1987) understand liking to be a matter of desiring, an attitude that at best involves its object having only instrumental (and not intrinsic) value. Yet this seems inadequate: surely there are attitudes towards persons intermediate between having a desire with a person as its object and loving the person. I can care about a person for her own sake and not merely instrumentally, and yet such caring does not on its own amount to (non-deficiently) loving her, for it seems I can care about my dog in exactly the same way, a kind of caring which is insufficiently personal for love.

It is more common to distinguish loving from liking via the intuition that the “depth” of love is to be explained in terms of a notion of identification: to love someone is somehow to identify yourself with him, whereas no such notion of identification is involved in liking. As Nussbaum puts it, “The choice between one potential love and another can feel, and be, like a choice of a way of life, a decision to dedicate oneself to these values rather than these” (1990, p. 328); liking clearly does not have this sort of “depth” (see also Helm 2010; Bagley 2015). Whether love involves some kind of identification, and if so exactly how to understand such identification, is a central bone of contention among the various analyses of love. In particular, Whiting (2013) argues that the appeal to a notion of identification distorts our understanding of the sort of motivation love can provide, for taken literally it implies that love motivates through self -interest rather than through the beloved’s interests. Thus, Whiting argues, central to love is the possibility that love takes the lover “outside herself”, potentially forgetting herself in being moved directly by the interests of the beloved. (Of course, we need not take the notion of identification literally in this way: in identifying with one’s beloved, one might have a concern for one’s beloved that is analogous to one’s concern for oneself; see Helm 2010.)

Another common way to distinguish love from other personal attitudes is in terms of a distinctive kind of evaluation, which itself can account for love’s “depth.” Again, whether love essentially involves a distinctive kind of evaluation, and if so how to make sense of that evaluation, is hotly disputed. Closely related to questions of evaluation are questions of justification: can we justify loving or continuing to love a particular person, and if so, how? For those who think the justification of love is possible, it is common to understand such justification in terms of evaluation, and the answers here affect various accounts’ attempts to make sense of the kind of constancy or commitment love seems to involve, as well as the sense in which love is directed at particular individuals.

In what follows, theories of love are tentatively and hesitantly classified into four types: love as union, love as robust concern, love as valuing, and love as an emotion. It should be clear, however, that particular theories classified under one type sometimes also include, without contradiction, ideas central to other types. The types identified here overlap to some extent, and in some cases classifying particular theories may involve excessive pigeonholing. (Such cases are noted below.) Part of the classificatory problem is that many accounts of love are quasi-reductionistic, understanding love in terms of notions like affection, evaluation, attachment, etc., which themselves never get analyzed. Even when these accounts eschew explicitly reductionistic language, very often little attempt is made to show how one such “aspect” of love is conceptually connected to others. As a result, there is no clear and obvious way to classify particular theories, let alone identify what the relevant classes should be.

The union view claims that love consists in the formation of (or the desire to form) some significant kind of union, a “we.” A central task for union theorists, therefore, is to spell out just what such a “we” comes to—whether it is literally a new entity in the world somehow composed of the lover and the beloved, or whether it is merely metaphorical. Variants of this view perhaps go back to Aristotle (cf. Sherman 1993) and can also be found in Montaigne ([E]) and Hegel (1997); contemporary proponents include Solomon (1981, 1988), Scruton (1986), Nozick (1989), Fisher (1990), and Delaney (1996).

Scruton, writing in particular about romantic love, claims that love exists “just so soon as reciprocity becomes community: that is, just so soon as all distinction between my interests and your interests is overcome” (1986, p. 230). The idea is that the union is a union of concern, so that when I act out of that concern it is not for my sake alone or for your sake alone but for our sake. Fisher (1990) holds a similar, but somewhat more moderate view, claiming that love is a partial fusion of the lovers’ cares, concerns, emotional responses, and actions. What is striking about both Scruton and Fisher is the claim that love requires the actual union of the lovers’ concerns, for it thus becomes clear that they conceive of love not so much as an attitude we take towards another but as a relationship: the distinction between your interests and mine genuinely disappears only when we together come to have shared cares, concerns, etc., and my merely having a certain attitude towards you is not enough for love. This provides content to the notion of a “we” as the (metaphorical?) subject of these shared cares and concerns, and as that for whose sake we act.

Solomon (1988) offers a union view as well, though one that tries “to make new sense out of ‘love’ through a literal rather than metaphoric sense of the ‘fusion’ of two souls” (p. 24, cf. Solomon 1981; however, it is unclear exactly what he means by a “soul” here and so how love can be a “literal” fusion of two souls). What Solomon has in mind is the way in which, through love, the lovers redefine their identities as persons in terms of the relationship: “Love is the concentration and the intensive focus of mutual definition on a single individual, subjecting virtually every personal aspect of one’s self to this process” (1988, p. 197). The result is that lovers come to share the interests, roles, virtues, and so on that constitute what formerly was two individual identities but now has become a shared identity, and they do so in part by each allowing the other to play an important role in defining his own identity.

Nozick (1989) offers a union view that differs from those of Scruton, Fisher, and Solomon in that Nozick thinks that what is necessary for love is merely the desire to form a “we,” together with the desire that your beloved reciprocates. Nonetheless, he claims that this “we” is “a new entity in the world…created by a new web of relationships between [the lovers] which makes them no longer separate” (p. 70). In spelling out this web of relationships, Nozick appeals to the lovers “pooling” not only their well-beings, in the sense that the well-being of each is tied up with that of the other, but also their autonomy, in that “each transfers some previous rights to make certain decisions unilaterally into a joint pool” (p. 71). In addition, Nozick claims, the lovers each acquire a new identity as a part of the “we,” a new identity constituted by their (a) wanting to be perceived publicly as a couple, (b) their attending to their pooled well-being, and (c) their accepting a “certain kind of division of labor” (p. 72):

A person in a we might find himself coming across something interesting to read yet leaving it for the other person, not because he himself would not be interested in it but because the other would be more interested, and one of them reading it is sufficient for it to be registered by the wider identity now shared, the we . [ 3 ]

Opponents of the union view have seized on claims like this as excessive: union theorists, they claim, take too literally the ontological commitments of this notion of a “we.” This leads to two specific criticisms of the union view. The first is that union views do away with individual autonomy. Autonomy, it seems, involves a kind of independence on the part of the autonomous agent, such that she is in control over not only what she does but also who she is, as this is constituted by her interests, values, concerns, etc. However, union views, by doing away with a clear distinction between your interests and mine, thereby undermine this sort of independence and so undermine the autonomy of the lovers. If autonomy is a part of the individual’s good, then, on the union view, love is to this extent bad; so much the worse for the union view (Singer 1994; Soble 1997). Moreover, Singer (1994) argues that a necessary part of having your beloved be the object of your love is respect for your beloved as the particular person she is, and this requires respecting her autonomy.

Union theorists have responded to this objection in several ways. Nozick (1989) seems to think of a loss of autonomy in love as a desirable feature of the sort of union lovers can achieve. Fisher (1990), somewhat more reluctantly, claims that the loss of autonomy in love is an acceptable consequence of love. Yet without further argument these claims seem like mere bullet biting. Solomon (1988, pp. 64ff) describes this “tension” between union and autonomy as “the paradox of love.” However, this a view that Soble (1997) derides: merely to call it a paradox, as Solomon does, is not to face up to the problem.

The second criticism involves a substantive view concerning love. Part of what it is to love someone, these opponents say, is to have concern for him for his sake. However, union views make such concern unintelligible and eliminate the possibility of both selfishness and self-sacrifice, for by doing away with the distinction between my interests and your interests they have in effect turned your interests into mine and vice versa (Soble 1997; see also Blum 1980, 1993). Some advocates of union views see this as a point in their favor: we need to explain how it is I can have concern for people other than myself, and the union view apparently does this by understanding your interests to be part of my own. And Delaney, responding to an apparent tension between our desire to be loved unselfishly (for fear of otherwise being exploited) and our desire to be loved for reasons (which presumably are attractive to our lover and hence have a kind of selfish basis), says (1996, p. 346):

Given my view that the romantic ideal is primarily characterized by a desire to achieve a profound consolidation of needs and interests through the formation of a we , I do not think a little selfishness of the sort described should pose a worry to either party.

The objection, however, lies precisely in this attempt to explain my concern for my beloved egoistically. As Whiting (1991, p. 10) puts it, such an attempt “strikes me as unnecessary and potentially objectionable colonization”: in love, I ought to be concerned with my beloved for her sake, and not because I somehow get something out of it. (This can be true whether my concern with my beloved is merely instrumental to my good or whether it is partly constitutive of my good.)

Although Whiting’s and Soble’s criticisms here succeed against the more radical advocates of the union view, they in part fail to acknowledge the kernel of truth to be gleaned from the idea of union. Whiting’s way of formulating the second objection in terms of an unnecessary egoism in part points to a way out: we persons are in part social creatures, and love is one profound mode of that sociality. Indeed, part of the point of union accounts is to make sense of this social dimension: to make sense of a way in which we can sometimes identify ourselves with others not merely in becoming interdependent with them (as Singer 1994, p. 165, suggests, understanding ‘interdependence’ to be a kind of reciprocal benevolence and respect) but rather in making who we are as persons be constituted in part by those we love (cf., e.g., Rorty 1986/1993; Nussbaum 1990).

Along these lines, Friedman (1998), taking her inspiration in part from Delaney (1996), argues that we should understand the sort of union at issue in love to be a kind of federation of selves:

On the federation model, a third unified entity is constituted by the interaction of the lovers, one which involves the lovers acting in concert across a range of conditions and for a range of purposes. This concerted action, however, does not erase the existence of the two lovers as separable and separate agents with continuing possibilities for the exercise of their own respective agencies. [p. 165]

Given that on this view the lovers do not give up their individual identities, there is no principled reason why the union view cannot make sense of the lover’s concern for her beloved for his sake. [ 4 ] Moreover, Friedman argues, once we construe union as federation, we can see that autonomy is not a zero-sum game; rather, love can both directly enhance the autonomy of each and promote the growth of various skills, like realistic and critical self-evaluation, that foster autonomy.

Nonetheless, this federation model is not without its problems—problems that affect other versions of the union view as well. For if the federation (or the “we”, as on Nozick’s view) is understood as a third entity, we need a clearer account than has been given of its ontological status and how it comes to be. Relevant here is the literature on shared intention and plural subjects. Gilbert (1989, 1996, 2000) has argued that we should take quite seriously the existence of a plural subject as an entity over and above its constituent members. Others, such as Tuomela (1984, 1995), Searle (1990), and Bratman (1999) are more cautious, treating such talk of “us” having an intention as metaphorical.

As this criticism of the union view indicates, many find caring about your beloved for her sake to be a part of what it is to love her. The robust concern view of love takes this to be the central and defining feature of love (cf. Taylor 1976; Newton-Smith 1989; Soble 1990, 1997; LaFollette 1996; Frankfurt 1999; White 2001). As Taylor puts it:

To summarize: if x loves y then x wants to benefit and be with y etc., and he has these wants (or at least some of them) because he believes y has some determinate characteristics ψ in virtue of which he thinks it worth while to benefit and be with y . He regards satisfaction of these wants as an end and not as a means towards some other end. [p. 157]

In conceiving of my love for you as constituted by my concern for you for your sake, the robust concern view rejects the idea, central to the union view, that love is to be understood in terms of the (literal or metaphorical) creation of a “we”: I am the one who has this concern for you, though it is nonetheless disinterested and so not egoistic insofar as it is for your sake rather than for my own. [ 5 ]

At the heart of the robust concern view is the idea that love “is neither affective nor cognitive. It is volitional” (Frankfurt 1999, p. 129; see also Martin 2015). Frankfurt continues:

That a person cares about or that he loves something has less to do with how things make him feel, or with his opinions about them, than with the more or less stable motivational structures that shape his preferences and that guide and limit his conduct.

This account analyzes caring about someone for her sake as a matter of being motivated in certain ways, in part as a response to what happens to one’s beloved. Of course, to understand love in terms of desires is not to leave other emotional responses out in the cold, for these emotions should be understood as consequences of desires. Thus, just as I can be emotionally crushed when one of my strong desires is disappointed, so too I can be emotionally crushed when things similarly go badly for my beloved. In this way Frankfurt (1999) tacitly, and White (2001) more explicitly, acknowledge the way in which my caring for my beloved for her sake results in my identity being transformed through her influence insofar as I become vulnerable to things that happen to her.

Not all robust concern theorists seem to accept this line, however; in particular, Taylor (1976) and Soble (1990) seem to have a strongly individualistic conception of persons that prevents my identity being bound up with my beloved in this sort of way, a kind of view that may seem to undermine the intuitive “depth” that love seems to have. (For more on this point, see Rorty 1986/1993.) In the middle is Stump (2006), who follows Aquinas in understanding love to involve not only the desire for your beloved’s well-being but also a desire for a certain kind of relationship with your beloved—as a parent or spouse or sibling or priest or friend, for example—a relationship within which you share yourself with and connect yourself to your beloved. [ 6 ]

One source of worry about the robust concern view is that it involves too passive an understanding of one’s beloved (Ebels-Duggan 2008). The thought is that on the robust concern view the lover merely tries to discover what the beloved’s well-being consists in and then acts to promote that, potentially by thwarting the beloved’s own efforts when the lover thinks those efforts would harm her well-being. This, however, would be disrespectful and demeaning, not the sort of attitude that love is. What robust concern views seem to miss, Ebels-Duggan suggests, is the way love involves interacting agents, each with a capacity for autonomy the recognition and engagement with which is an essential part of love. In response, advocates of the robust concern view might point out that promoting someone’s well-being normally requires promoting her autonomy (though they may maintain that this need not always be true: that paternalism towards a beloved can sometimes be justified and appropriate as an expression of one’s love). Moreover, we might plausibly think, it is only through the exercise of one’s autonomy that one can define one’s own well-being as a person, so that a lover’s failure to respect the beloved’s autonomy would be a failure to promote her well-being and therefore not an expression of love, contrary to what Ebels-Duggan suggests. Consequently, it might seem, robust concern views can counter this objection by offering an enriched conception of what it is to be a person and so of the well-being of persons.

Another source of worry is that the robust concern view offers too thin a conception of love. By emphasizing robust concern, this view understands other features we think characteristic of love, such as one’s emotional responsiveness to one’s beloved, to be the effects of that concern rather than constituents of it. Thus Velleman (1999) argues that robust concern views, by understanding love merely as a matter of aiming at a particular end (viz., the welfare of one’s beloved), understand love to be merely conative. However, he claims, love can have nothing to do with desires, offering as a counterexample the possibility of loving a troublemaking relation whom you do not want to be with, whose well being you do not want to promote, etc. Similarly, Badhwar (2003) argues that such a “teleological” view of love makes it mysterious how “we can continue to love someone long after death has taken him beyond harm or benefit” (p. 46). Moreover Badhwar argues, if love is essentially a desire, then it implies that we lack something; yet love does not imply this and, indeed, can be felt most strongly at times when we feel our lives most complete and lacking in nothing. Consequently, Velleman and Badhwar conclude, love need not involve any desire or concern for the well-being of one’s beloved.

This conclusion, however, seems too hasty, for such examples can be accommodated within the robust concern view. Thus, the concern for your relative in Velleman’s example can be understood to be present but swamped by other, more powerful desires to avoid him. Indeed, keeping the idea that you want to some degree to benefit him, an idea Velleman rejects, seems to be essential to understanding the conceptual tension between loving someone and not wanting to help him, a tension Velleman does not fully acknowledge. Similarly, continued love for someone who has died can be understood on the robust concern view as parasitic on the former love you had for him when he was still alive: your desires to benefit him get transformed, through your subsequent understanding of the impossibility of doing so, into wishes. [ 7 ] Finally, the idea of concern for your beloved’s well-being need not imply the idea that you lack something, for such concern can be understood in terms of the disposition to be vigilant for occasions when you can come to his aid and consequently to have the relevant occurrent desires. All of this seems fully compatible with the robust concern view.

One might also question whether Velleman and Badhwar make proper use of their examples of loving your meddlesome relation or someone who has died. For although we can understand these as genuine cases of love, they are nonetheless deficient cases and ought therefore be understood as parasitic on the standard cases. Readily to accommodate such deficient cases of love into a philosophical analysis as being on a par with paradigm cases, and to do so without some special justification, is dubious.

Nonetheless, the robust concern view as it stands does not seem properly able to account for the intuitive “depth” of love and so does not seem properly to distinguish loving from liking. Although, as noted above, the robust concern view can begin to make some sense of the way in which the lover’s identity is altered by the beloved, it understands this only an effect of love, and not as a central part of what love consists in.

This vague thought is nicely developed by Wonderly (2017), who emphasizes that in addition to the sort of disinterested concern for another that is central to robust-concern accounts of love, an essential part of at least romantic love is the idea that in loving someone I must find them to be not merely important for their own sake but also important to me . Wonderly (2017) fleshes out what this “importance to me” involves in terms of the idea of attachment (developed in Wonderly 2016) that she argues can make sense of the intimacy and depth of love from within what remains fundamentally a robust-concern account. [ 8 ]

4. Love as Valuing

A third kind of view of love understands love to be a distinctive mode of valuing a person. As the distinction between eros and agape in Section 1 indicates, there are at least two ways to construe this in terms of whether the lover values the beloved because she is valuable, or whether the beloved comes to be valuable to the lover as a result of her loving him. The former view, which understands the lover as appraising the value of the beloved in loving him, is the topic of Section 4.1 , whereas the latter view, which understands her as bestowing value on him, will be discussed in Section 4.2 .

Velleman (1999, 2008) offers an appraisal view of love, understanding love to be fundamentally a matter of acknowledging and responding in a distinctive way to the value of the beloved. (For a very different appraisal view of love, see Kolodny 2003.) Understanding this more fully requires understanding both the kind of value of the beloved to which one responds and the distinctive kind of response to such value that love is. Nonetheless, it should be clear that what makes an account be an appraisal view of love is not the mere fact that love is understood to involve appraisal; many other accounts do so, and it is typical of robust concern accounts, for example (cf. the quote from Taylor above , Section 3 ). Rather, appraisal views are distinctive in understanding love to consist in that appraisal.

In articulating the kind of value love involves, Velleman, following Kant, distinguishes dignity from price. To have a price , as the economic metaphor suggests, is to have a value that can be compared to the value of other things with prices, such that it is intelligible to exchange without loss items of the same value. By contrast, to have dignity is to have a value such that comparisons of relative value become meaningless. Material goods are normally understood to have prices, but we persons have dignity: no substitution of one person for another can preserve exactly the same value, for something of incomparable worth would be lost (and gained) in such a substitution.

On this Kantian view, our dignity as persons consists in our rational nature: our capacity both to be actuated by reasons that we autonomously provide ourselves in setting our own ends and to respond appropriately to the intrinsic values we discover in the world. Consequently, one important way in which we exercise our rational natures is to respond with respect to the dignity of other persons (a dignity that consists in part in their capacity for respect): respect just is the required minimal response to the dignity of persons. What makes a response to a person be that of respect, Velleman claims, still following Kant, is that it “arrests our self-love” and thereby prevents us from treating him as a means to our ends (p. 360).

Given this, Velleman claims that love is similarly a response to the dignity of persons, and as such it is the dignity of the object of our love that justifies that love. However, love and respect are different kinds of responses to the same value. For love arrests not our self-love but rather

our tendencies toward emotional self-protection from another person, tendencies to draw ourselves in and close ourselves off from being affected by him. Love disarms our emotional defenses; it makes us vulnerable to the other. [1999, p. 361]

This means that the concern, attraction, sympathy, etc. that we normally associate with love are not constituents of love but are rather its normal effects, and love can remain without them (as in the case of the love for a meddlesome relative one cannot stand being around). Moreover, this provides Velleman with a clear account of the intuitive “depth” of love: it is essentially a response to persons as such, and to say that you love your dog is therefore to be confused.

Of course, we do not respond with love to the dignity of every person we meet, nor are we somehow required to: love, as the disarming of our emotional defenses in a way that makes us especially vulnerable to another, is the optional maximal response to others’ dignity. What, then, explains the selectivity of love—why I love some people and not others? The answer lies in the contingent fit between the way some people behaviorally express their dignity as persons and the way I happen to respond to those expressions by becoming emotionally vulnerable to them. The right sort of fit makes someone “lovable” by me (1999, p. 372), and my responding with love in these cases is a matter of my “really seeing” this person in a way that I fail to do with others who do not fit with me in this way. By ‘lovable’ here Velleman seems to mean able to be loved, not worthy of being loved, for nothing Velleman says here speaks to a question about the justification of my loving this person rather than that. Rather, what he offers is an explanation of the selectivity of my love, an explanation that as a matter of fact makes my response be that of love rather than mere respect.

This understanding of the selectivity of love as something that can be explained but not justified is potentially troubling. For we ordinarily think we can justify not only my loving you rather than someone else but also and more importantly the constancy of my love: my continuing to love you even as you change in certain fundamental ways (but not others). As Delaney (1996, p. 347) puts the worry about constancy:

while you seem to want it to be true that, were you to become a schmuck, your lover would continue to love you,…you also want it to be the case that your lover would never love a schmuck.

The issue here is not merely that we can offer explanations of the selectivity of my love, of why I do not love schmucks; rather, at issue is the discernment of love, of loving and continuing to love for good reasons as well as of ceasing to love for good reasons. To have these good reasons seems to involve attributing different values to you now rather than formerly or rather than to someone else, yet this is precisely what Velleman denies is the case in making the distinction between love and respect the way he does.

It is also questionable whether Velleman can even explain the selectivity of love in terms of the “fit” between your expressions and my sensitivities. For the relevant sensitivities on my part are emotional sensitivities: the lowering of my emotional defenses and so becoming emotionally vulnerable to you. Thus, I become vulnerable to the harms (or goods) that befall you and so sympathetically feel your pain (or joy). Such emotions are themselves assessable for warrant, and now we can ask why my disappointment that you lost the race is warranted, but my being disappointed that a mere stranger lost would not be warranted. The intuitive answer is that I love you but not him. However, this answer is unavailable to Velleman, because he thinks that what makes my response to your dignity that of love rather than respect is precisely that I feel such emotions, and to appeal to my love in explaining the emotions therefore seems viciously circular.

Although these problems are specific to Velleman’s account, the difficulty can be generalized to any appraisal account of love (such as that offered in Kolodny 2003). For if love is an appraisal, it needs to be distinguished from other forms of appraisal, including our evaluative judgments. On the one hand, to try to distinguish love as an appraisal from other appraisals in terms of love’s having certain effects on our emotional and motivational life (as on Velleman’s account) is unsatisfying because it ignores part of what needs to be explained: why the appraisal of love has these effects and yet judgments with the same evaluative content do not. Indeed, this question is crucial if we are to understand the intuitive “depth” of love, for without an answer to this question we do not understand why love should have the kind of centrality in our lives it manifestly does. [ 9 ] On the other hand, to bundle this emotional component into the appraisal itself would be to turn the view into either the robust concern view ( Section 3 ) or a variant of the emotion view ( Section 5.1 ).

In contrast to Velleman, Singer (1991, 1994, 2009) understands love to be fundamentally a matter of bestowing value on the beloved. To bestow value on another is to project a kind of intrinsic value onto him. Indeed, this fact about love is supposed to distinguish love from liking: “Love is an attitude with no clear objective,” whereas liking is inherently teleological (1991, p. 272). As such, there are no standards of correctness for bestowing such value, and this is how love differs from other personal attitudes like gratitude, generosity, and condescension: “love…confers importance no matter what the object is worth” (p. 273). Consequently, Singer thinks, love is not an attitude that can be justified in any way.

What is it, exactly, to bestow this kind of value on someone? It is, Singer says, a kind of attachment and commitment to the beloved, in which one comes to treat him as an end in himself and so to respond to his ends, interests, concerns, etc. as having value for their own sake. This means in part that the bestowal of value reveals itself “by caring about the needs and interests of the beloved, by wishing to benefit or protect her, by delighting in her achievements,” etc. (p. 270). This sounds very much like the robust concern view, yet the bestowal view differs in understanding such robust concern to be the effect of the bestowal of value that is love rather than itself what constitutes love: in bestowing value on my beloved, I make him be valuable in such a way that I ought to respond with robust concern.

For it to be intelligible that I have bestowed value on someone, I must therefore respond appropriately to him as valuable, and this requires having some sense of what his well-being is and of what affects that well-being positively or negatively. Yet having this sense requires in turn knowing what his strengths and deficiencies are, and this is a matter of appraising him in various ways. Bestowal thus presupposes a kind of appraisal, as a way of “really seeing” the beloved and attending to him. Nonetheless, Singer claims, it is the bestowal that is primary for understanding what love consists in: the appraisal is required only so that the commitment to one’s beloved and his value as thus bestowed has practical import and is not “a blind submission to some unknown being” (1991, p. 272; see also Singer 1994, pp. 139ff).

Singer is walking a tightrope in trying to make room for appraisal in his account of love. Insofar as the account is fundamentally a bestowal account, Singer claims that love cannot be justified, that we bestow the relevant kind of value “gratuitously.” This suggests that love is blind, that it does not matter what our beloved is like, which seems patently false. Singer tries to avoid this conclusion by appealing to the role of appraisal: it is only because we appraise another as having certain virtues and vices that we come to bestow value on him. Yet the “because” here, since it cannot justify the bestowal, is at best a kind of contingent causal explanation. [ 10 ] In this respect, Singer’s account of the selectivity of love is much the same as Velleman’s, and it is liable to the same criticism: it makes unintelligible the way in which our love can be discerning for better or worse reasons. Indeed, this failure to make sense of the idea that love can be justified is a problem for any bestowal view. For either (a) a bestowal itself cannot be justified (as on Singer’s account), in which case the justification of love is impossible, or (b) a bestowal can be justified, in which case it is hard to make sense of value as being bestowed rather than there antecedently in the object as the grounds of that “bestowal.”

More generally, a proponent of the bestowal view needs to be much clearer than Singer is in articulating precisely what a bestowal is. What is the value that I create in a bestowal, and how can my bestowal create it? On a crude Humean view, the answer might be that the value is something projected onto the world through my pro-attitudes, like desire. Yet such a view would be inadequate, since the projected value, being relative to a particular individual, would do no theoretical work, and the account would essentially be a variant of the robust concern view. Moreover, in providing a bestowal account of love, care is needed to distinguish love from other personal attitudes such as admiration and respect: do these other attitudes involve bestowal? If so, how does the bestowal in these cases differ from the bestowal of love? If not, why not, and what is so special about love that requires a fundamentally different evaluative attitude than admiration and respect?

Nonetheless, there is a kernel of truth in the bestowal view: there is surely something right about the idea that love is creative and not merely a response to antecedent value, and accounts of love that understand the kind of evaluation implicit in love merely in terms of appraisal seem to be missing something. Precisely what may be missed will be discussed below in Section 6 .

Perhaps there is room for an understanding of love and its relation to value that is intermediate between appraisal and bestowal accounts. After all, if we think of appraisal as something like perception, a matter of responding to what is out there in the world, and of bestowal as something like action, a matter of doing something and creating something, we should recognize that the responsiveness central to appraisal may itself depend on our active, creative choices. Thus, just as we must recognize that ordinary perception depends on our actively directing our attention and deploying concepts, interpretations, and even arguments in order to perceive things accurately, so too we might think our vision of our beloved’s valuable properties that is love also depends on our actively attending to and interpreting him. Something like this is Jollimore’s view (2011). According to Jollimore, in loving someone we actively attend to his valuable properties in a way that we take to provide us with reasons to treat him preferentially. Although we may acknowledge that others might have such properties even to a greater degree than our beloved does, we do not attend to and appreciate such properties in others in the same way we do those in our beloveds; indeed, we find our appreciation of our beloved’s valuable properties to “silence” our similar appreciation of those in others. (In this way, Jollimore thinks, we can solve the problem of fungibility, discussed below in Section 6 .) Likewise, in perceiving our beloved’s actions and character, we do so through the lens of such an appreciation, which will tend as to “silence” interpretations inconsistent with that appreciation. In this way, love involves finding one’s beloved to be valuable in a way that involves elements of both appraisal (insofar as one must thereby be responsive to valuable properties one’s beloved really has) and bestowal (insofar as through one’s attention and committed appreciation of these properties they come to have special significance for one).

One might object that this conception of love as silencing the special value of others or to negative interpretations of our beloveds is irrational in a way that love is not. For, it might seem, such “silencing” is merely a matter of our blinding ourselves to how things really are. Yet Jollimore claims that this sense in which love is blind is not objectionable, for (a) we can still intellectually recognize the things that love’s vision silences, and (b) there really is no impartial perspective we can take on the values things have, and love is one appropriate sort of partial perspective from which the value of persons can be manifest. Nonetheless, one might wonder about whether that perspective of love itself can be distorted and what the norms are in terms of which such distortions are intelligible. Furthermore, it may seem that Jollimore’s attempt to reconcile appraisal and bestowal fails to appreciate the underlying metaphysical difficulty: appraisal is a response to value that is antecedently there, whereas bestowal is the creation of value that was not antecedently there. Consequently, it might seem, appraisal and bestowal are mutually exclusive and cannot be reconciled in the way Jollimore hopes.

Whereas Jollimore tries to combine separate elements of appraisal and of bestowal in a single account, Helm (2010) and Bagley (2015) offer accounts that reject the metaphysical presupposition that values must be either prior to love (as with appraisal) or posterior to love (as with bestowal), instead understanding the love and the values to emerge simultaneously. Thus, Helm presents a detailed account of valuing in terms of the emotions, arguing that while we can understand individual emotions as appraisals , responding to values already their in their objects, these values are bestowed on those objects via broad, holistic patterns of emotions. How this amounts to an account of love will be discussed in Section 5.2 , below. Bagley (2015) instead appeals to a metaphor of improvisation, arguing that just as jazz musicians jointly make determinate the content of their musical ideas through on-going processes of their expression, so too lovers jointly engage in “deep improvisation”, thereby working out of their values and identities through the on-going process of living their lives together. These values are thus something the lovers jointly construct through the process of recognizing and responding to those very values. To love someone is thus to engage with them as partners in such “deep improvisation”. (This account is similar to Helm (2008, 2010)’s account of plural agency, which he uses to provide an account of friendship and other loving relationships; see the discussion of shared activity in the entry on friendship .)

5. Emotion Views

Given these problems with the accounts of love as valuing, perhaps we should turn to the emotions. For emotions just are responses to objects that combine evaluation, motivation, and a kind of phenomenology, all central features of the attitude of love.

Many accounts of love claim that it is an emotion; these include: Wollheim 1984, Rorty 1986/1993, Brown 1987, Hamlyn 1989, Baier 1991, and Badhwar 2003. [ 11 ] Thus, Hamlyn (1989, p. 219) says:

It would not be a plausible move to defend any theory of the emotions to which love and hate seemed exceptions by saying that love and hate are after all not emotions. I have heard this said, but it does seem to me a desperate move to make. If love and hate are not emotions what is?

The difficulty with this claim, as Rorty (1980) argues, is that the word, ‘emotion,’ does not seem to pick out a homogeneous collection of mental states, and so various theories claiming that love is an emotion mean very different things. Consequently, what are here labeled “emotion views” are divided into those that understand love to be a particular kind of evaluative-cum-motivational response to an object, whether that response is merely occurrent or dispositional (‘emotions proper,’ see Section 5.1 , below), and those that understand love to involve a collection of related and interconnected emotions proper (‘emotion complexes,’ see Section 5.2 , below).

An emotion proper is a kind of “evaluative-cum-motivational response to an object”; what does this mean? Emotions are generally understood to have several objects. The target of an emotion is that at which the emotion is directed: if I am afraid or angry at you, then you are the target. In responding to you with fear or anger, I am implicitly evaluating you in a particular way, and this evaluation—called the formal object —is the kind of evaluation of the target that is distinctive of a particular emotion type. Thus, in fearing you, I implicitly evaluate you as somehow dangerous, whereas in being angry at you I implicitly evaluate you as somehow offensive. Yet emotions are not merely evaluations of their targets; they in part motivate us to behave in certain ways, both rationally (by motivating action to avoid the danger) and arationally (via certain characteristic expressions, such as slamming a door out of anger). Moreover, emotions are generally understood to involve a phenomenological component, though just how to understand the characteristic “feel” of an emotion and its relation to the evaluation and motivation is hotly disputed. Finally, emotions are typically understood to be passions: responses that we feel imposed on us as if from the outside, rather than anything we actively do. (For more on the philosophy of emotions, see entry on emotion .)

What then are we saying when we say that love is an emotion proper? According to Brown (1987, p. 14), emotions as occurrent mental states are “abnormal bodily changes caused by the agent’s evaluation or appraisal of some object or situation that the agent believes to be of concern to him or her.” He spells this out by saying that in love, we “cherish” the person for having “a particular complex of instantiated qualities” that is “open-ended” so that we can continue to love the person even as she changes over time (pp. 106–7). These qualities, which include historical and relational qualities, are evaluated in love as worthwhile. [ 12 ] All of this seems aimed at spelling out what love’s formal object is, a task that is fundamental to understanding love as an emotion proper. Thus, Brown seems to say that love’s formal object is just being worthwhile (or, given his examples, perhaps: worthwhile as a person), and he resists being any more specific than this in order to preserve the open-endedness of love. Hamlyn (1989) offers a similar account, saying (p. 228):

With love the difficulty is to find anything of this kind [i.e., a formal object] which is uniquely appropriate to love. My thesis is that there is nothing of this kind that must be so, and that this differentiates it and hate from the other emotions.

Hamlyn goes on to suggest that love and hate might be primordial emotions, a kind of positive or negative “feeling towards,” presupposed by all other emotions. [ 13 ]

The trouble with these accounts of love as an emotion proper is that they provide too thin a conception of love. In Hamlyn’s case, love is conceived as a fairly generic pro-attitude, rather than as the specific kind of distinctively personal attitude discussed here. In Brown’s case, spelling out the formal object of love as simply being worthwhile (as a person) fails to distinguish love from other evaluative responses like admiration and respect. Part of the problem seems to be the rather simple account of what an emotion is that Brown and Hamlyn use as their starting point: if love is an emotion, then the understanding of what an emotion is must be enriched considerably to accommodate love. Yet it is not at all clear whether the idea of an “emotion proper” can be adequately enriched so as to do so. As Pismenny & Prinz (2017) point out, love seems to be too varied both in its ground and in the sort of experience it involves to be capturable by a single emotion.

The emotion complex view, which understands love to be a complex emotional attitude towards another person, may initially seem to hold out great promise to overcome the problems of alternative types of views. By articulating the emotional interconnections between persons, it could offer a satisfying account of the “depth” of love without the excesses of the union view and without the overly narrow teleological focus of the robust concern view; and because these emotional interconnections are themselves evaluations, it could offer an understanding of love as simultaneously evaluative, without needing to specify a single formal object of love. However, the devil is in the details.

Rorty (1986/1993) does not try to present a complete account of love; rather, she focuses on the idea that “relational psychological attitudes” which, like love, essentially involve emotional and desiderative responses, exhibit historicity : “they arise from, and are shaped by, dynamic interactions between a subject and an object” (p. 73). In part this means that what makes an attitude be one of love is not the presence of a state that we can point to at a particular time within the lover; rather, love is to be “identified by a characteristic narrative history” (p. 75). Moreover, Rorty argues, the historicity of love involves the lover’s being permanently transformed by loving who he does.

Baier (1991), seeming to pick up on this understanding of love as exhibiting historicity, says (p. 444):

Love is not just an emotion people feel toward other people, but also a complex tying together of the emotions that two or a few more people have; it is a special form of emotional interdependence.

To a certain extent, such emotional interdependence involves feeling sympathetic emotions, so that, for example, I feel disappointed and frustrated on behalf of my beloved when she fails, and joyful when she succeeds. However, Baier insists, love is “more than just the duplication of the emotion of each in a sympathetic echo in the other” (p. 442); the emotional interdependence of the lovers involves also appropriate follow-up responses to the emotional predicaments of your beloved. Two examples Baier gives (pp. 443–44) are a feeling of “mischievous delight” at your beloved’s temporary bafflement, and amusement at her embarrassment. The idea is that in a loving relationship your beloved gives you permission to feel such emotions when no one else is permitted to do so, and a condition of her granting you that permission is that you feel these emotions “tenderly.” Moreover, you ought to respond emotionally to your beloved’s emotional responses to you: by feeling hurt when she is indifferent to you, for example. All of these foster the sort of emotional interdependence Baier is after—a kind of intimacy you have with your beloved.

Badhwar (2003, p. 46) similarly understands love to be a matter of “one’s overall emotional orientation towards a person—the complex of perceptions, thoughts, and feelings”; as such, love is a matter of having a certain “character structure.” Central to this complex emotional orientation, Badhwar thinks, is what she calls the “look of love”: “an ongoing [emotional] affirmation of the loved object as worthy of existence…for her own sake” (p. 44), an affirmation that involves taking pleasure in your beloved’s well-being. Moreover, Badhwar claims, the look of love also provides to the beloved reliable testimony concerning the quality of the beloved’s character and actions (p. 57).

There is surely something very right about the idea that love, as an attitude central to deeply personal relationships, should not be understood as a state that can simply come and go. Rather, as the emotion complex view insists, the complexity of love is to be found in the historical patterns of one’s emotional responsiveness to one’s beloved—a pattern that also projects into the future. Indeed, as suggested above, the kind of emotional interdependence that results from this complex pattern can seem to account for the intuitive “depth” of love as fully interwoven into one’s emotional sense of oneself. And it seems to make some headway in understanding the complex phenomenology of love: love can at times be a matter of intense pleasure in the presence of one’s beloved, yet it can at other times involve frustration, exasperation, anger, and hurt as a manifestation of the complexities and depth of the relationships it fosters.

This understanding of love as constituted by a history of emotional interdependence enables emotion complex views to say something interesting about the impact love has on the lover’s identity. This is partly Rorty’s point (1986/1993) in her discussion of the historicity of love ( above ). Thus, she argues, one important feature of such historicity is that love is “ dynamically permeable ” in that the lover is continually “changed by loving” such that these changes “tend to ramify through a person’s character” (p. 77). Through such dynamic permeability, love transforms the identity of the lover in a way that can sometimes foster the continuity of the love, as each lover continually changes in response to the changes in the other. [ 14 ] Indeed, Rorty concludes, love should be understood in terms of “a characteristic narrative history” (p. 75) that results from such dynamic permeability. It should be clear, however, that the mere fact of dynamic permeability need not result in the love’s continuing: nothing about the dynamics of a relationship requires that the characteristic narrative history project into the future, and such permeability can therefore lead to the dissolution of the love. Love is therefore risky—indeed, all the more risky because of the way the identity of the lover is defined in part through the love. The loss of a love can therefore make one feel no longer oneself in ways poignantly described by Nussbaum (1990).

By focusing on such emotionally complex histories, emotion complex views differ from most alternative accounts of love. For alternative accounts tend to view love as a kind of attitude we take toward our beloveds, something we can analyze simply in terms of our mental state at the moment. [ 15 ] By ignoring this historical dimension of love in providing an account of what love is, alternative accounts have a hard time providing either satisfying accounts of the sense in which our identities as person are at stake in loving another or satisfactory solutions to problems concerning how love is to be justified (cf. Section 6 , especially the discussion of fungibility ).

Nonetheless, some questions remain. If love is to be understood as an emotion complex, we need a much more explicit account of the pattern at issue here: what ties all of these emotional responses together into a single thing, namely love? Baier and Badhwar seem content to provide interesting and insightful examples of this pattern, but that does not seem to be enough. For example, what connects my amusement at my beloved’s embarrassment to other emotions like my joy on his behalf when he succeeds? Why shouldn’t my amusement at his embarrassment be understood instead as a somewhat cruel case of schadenfreude and so as antithetical to, and disconnected from, love? Moreover, as Naar (2013) notes, we need a principled account of when such historical patterns are disrupted in such a way as to end the love and when they are not. Do I stop loving when, in the midst of clinical depression, I lose my normal pattern of emotional concern?

Presumably the answer requires returning to the historicity of love: it all depends on the historical details of the relationship my beloved and I have forged. Some loves develop so that the intimacy within the relationship is such as to allow for tender, teasing responses to each other, whereas other loves may not. The historical details, together with the lovers’ understanding of their relationship, presumably determine which emotional responses belong to the pattern constitutive of love and which do not. However, this answer so far is inadequate: not just any historical relationship involving emotional interdependence is a loving relationship, and we need a principled way of distinguishing loving relationships from other relational evaluative attitudes: precisely what is the characteristic narrative history that is characteristic of love?

Helm (2009, 2010) tries to answer some of these questions in presenting an account of love as intimate identification. To love another, Helm claims, is to care about him as the particular person he is and so, other things being equal, to value the things he values. Insofar as a person’s (structured) set of values—his sense of the kind of life worth his living—constitutes his identity as a person, such sharing of values amounts to sharing his identity, which sounds very much like union accounts of love. However, Helm is careful to understand such sharing of values as for the sake of the beloved (as robust concern accounts insist), and he spells this all out in terms of patterns of emotions. Thus, Helm claims, all emotions have not only a target and a formal object (as indicated above), but also a focus : a background object the subject cares about in terms of which the implicit evaluation of the target is made intelligible. (For example, if I am afraid of the approaching hailstorm, I thereby evaluate it as dangerous, and what explains this evaluation is the way that hailstorm bears on my vegetable garden, which I care about; my garden, therefore, is the focus of my fear.) Moreover, emotions normally come in patterns with a common focus: fearing the hailstorm is normally connected to other emotions as being relieved when it passes by harmlessly (or disappointed or sad when it does not), being angry at the rabbits for killing the spinach, delighted at the productivity of the tomato plants, etc. Helm argues that a projectible pattern of such emotions with a common focus constitute caring about that focus. Consequently, we might say along the lines of Section 4.3 , while particular emotions appraise events in the world as having certain evaluative properties, their having these properties is partly bestowed on them by the overall patterns of emotions.

Helm identifies some emotions as person-focused emotions : emotions like pride and shame that essentially take persons as their focuses, for these emotions implicitly evaluate in terms of the target’s bearing on the quality of life of the person that is their focus. To exhibit a pattern of such emotions focused on oneself and subfocused on being a mother, for example, is to care about the place being a mother has in the kind of life you find worth living—in your identity as a person; to care in this way is to value being a mother as a part of your concern for your own identity. Likewise, to exhibit a projectible pattern of such emotions focused on someone else and subfocused on his being a father is to value this as a part of your concern for his identity—to value it for his sake. Such sharing of another’s values for his sake, which, Helm argues, essentially involves trust, respect, and affection, amounts to intimate identification with him, and such intimate identification just is love. Thus, Helm tries to provide an account of love that is grounded in an explicit account of caring (and caring about something for the sake of someone else) that makes room for the intuitive “depth” of love through intimate identification.

Jaworska & Wonderly (2017) argue that Helm’s construal of intimacy as intimate identification is too demanding. Rather, they argue, the sort of intimacy that distinguishes love from mere caring is one that involves a kind of emotional vulnerability in which things going well or poorly for one’s beloved are directly connected not merely to one’s well-being, but to one’s ability to flourish. This connection, they argue, runs through the lover’s self-understanding and the place the beloved has in the lover’s sense of a meaningful life.

Why do we love? It has been suggested above that any account of love needs to be able to answer some such justificatory question. Although the issue of the justification of love is important on its own, it is also important for the implications it has for understanding more clearly the precise object of love: how can we make sense of the intuitions not only that we love the individuals themselves rather than their properties, but also that my beloved is not fungible—that no one could simply take her place without loss. Different theories approach these questions in different ways, but, as will become clear below, the question of justification is primary.

One way to understand the question of why we love is as asking for what the value of love is: what do we get out of it? One kind of answer, which has its roots in Aristotle, is that having loving relationships promotes self-knowledge insofar as your beloved acts as a kind of mirror, reflecting your character back to you (Badhwar, 2003, p. 58). Of course, this answer presupposes that we cannot accurately know ourselves in other ways: that left alone, our sense of ourselves will be too imperfect, too biased, to help us grow and mature as persons. The metaphor of a mirror also suggests that our beloveds will be in the relevant respects similar to us, so that merely by observing them, we can come to know ourselves better in a way that is, if not free from bias, at least more objective than otherwise.

Brink (1999, pp. 264–65) argues that there are serious limits to the value of such mirroring of one’s self in a beloved. For if the aim is not just to know yourself better but to improve yourself, you ought also to interact with others who are not just like yourself: interacting with such diverse others can help you recognize alternative possibilities for how to live and so better assess the relative merits of these possibilities. Whiting (2013) also emphasizes the importance of our beloveds’ having an independent voice capable of reflecting not who one now is but an ideal for who one is to be. Nonetheless, we need not take the metaphor of the mirror quite so literally; rather, our beloveds can reflect our selves not through their inherent similarity to us but rather through the interpretations they offer of us, both explicitly and implicitly in their responses to us. This is what Badhwar calls the “epistemic significance” of love. [ 16 ]

In addition to this epistemic significance of love, LaFollette (1996, Chapter 5) offers several other reasons why it is good to love, reasons derived in part from the psychological literature on love: love increases our sense of well-being, it elevates our sense of self-worth, and it serves to develop our character. It also, we might add, tends to lower stress and blood pressure and to increase health and longevity. Friedman (1993) argues that the kind of partiality towards our beloveds that love involves is itself morally valuable because it supports relationships—loving relationships—that contribute “to human well-being, integrity, and fulfillment in life” (p. 61). And Solomon (1988, p. 155) claims:

Ultimately, there is only one reason for love. That one grand reason…is “because we bring out the best in each other.” What counts as “the best,” of course, is subject to much individual variation.

This is because, Solomon suggests, in loving someone, I want myself to be better so as to be worthy of his love for me.

Each of these answers to the question of why we love understands it to be asking about love quite generally, abstracted away from details of particular relationships. It is also possible to understand the question as asking about particular loves. Here, there are several questions that are relevant:

• What, if anything, justifies my loving rather than not loving this particular person?
• What, if anything, justifies my coming to love this particular person rather than someone else?
• What, if anything, justifies my continuing to love this particular person given the changes—both in him and me and in the overall circumstances—that have occurred since I began loving him?

These are importantly different questions. Velleman (1999), for example, thinks we can answer (1) by appealing to the fact that my beloved is a person and so has a rational nature, yet he thinks (2) and (3) have no answers: the best we can do is offer causal explanations for our loving particular people, a position echoed by Han (2021). Setiya (2014) similarly thinks (1) has an answer, but points not to the rational nature of persons but rather to the other’s humanity , where such humanity differs from personhood in that not all humans need have the requisite rational nature for personhood, and not all persons need be humans. And, as will become clear below , the distinction between (2) and (3) will become important in resolving puzzles concerning whether our beloveds are fungible, though it should be clear that (3) potentially raises questions concerning personal identity (which will not be addressed here).

It is important not to misconstrue these justificatory questions. Thomas (1991) , for example, rejects the idea that love can be justified: “there are no rational considerations whereby anyone can lay claim to another’s love or insist that an individual’s love for another is irrational” (p. 474). This is because, Thomas claims (p. 471):

no matter how wonderful and lovely an individual might be, on any and all accounts, it is simply false that a romantically unencumbered person must love that individual on pain of being irrational. Or, there is no irrationality involved in ceasing to love a person whom one once loved immensely, although the person has not changed.

However, as LaFollette (1996, p. 63) correctly points out,

reason is not some external power which dictates how we should behave, but an internal power, integral to who we are.… Reason does not command that we love anyone. Nonetheless, reason is vital in determining whom we love and why we love them.

That is, reasons for love are pro tanto : they are a part of the overall reasons we have for acting, and it is up to us in exercising our capacity for agency to decide what on balance we have reason to do or even whether we shall act contrary to our reasons. To construe the notion of a reason for love as compelling us to love, as Thomas does, is to misconstrue the place such reasons have within our agency. [ 17 ]

Most philosophical discussions of the justification of love focus on question (1) , thinking that answering this question will also, to the extent that we can, answer question (2) , which is typically not distinguished from (3) . The answers given to these questions vary in a way that turns on how the kind of evaluation implicit in love is construed. On the one hand, those who understand the evaluation implicit in love to be a matter of the bestowal of value (such as Telfer 1970–71; Friedman 1993; Singer 1994) typically claim that no justification can be given (cf. Section 4.2 ). As indicated above, this seems problematic, especially given the importance love can have both in our lives and, especially, in shaping our identities as persons. To reject the idea that we can love for reasons may reduce the impact our agency can have in defining who we are.

On the other hand, those who understand the evaluation implicit in love to be a matter of appraisal tend to answer the justificatory question by appeal to these valuable properties of the beloved. This acceptance of the idea that love can be justified leads to two further, related worries about the object of love.

The first worry is raised by Vlastos (1981) in a discussion Plato’s and Aristotle’s accounts of love. Vlastos notes that these accounts focus on the properties of our beloveds: we are to love people, they say, only because and insofar as they are objectifications of the excellences. Consequently, he argues, in doing so they fail to distinguish “ disinterested affection for the person we love” from “ appreciation of the excellences instantiated by that person ” (p. 33). That is, Vlastos thinks that Plato and Aristotle provide an account of love that is really a love of properties rather than a love of persons—love of a type of person, rather than love of a particular person—thereby losing what is distinctive about love as an essentially personal attitude. This worry about Plato and Aristotle might seem to apply just as well to other accounts that justify love in terms of the properties of the person: insofar as we love the person for the sake of her properties, it might seem that what we love is those properties and not the person. Here it is surely insufficient to say, as Solomon (1988, p. 154) does, “if love has its reasons, then it is not the whole person that one loves but certain aspects of that person—though the rest of the person comes along too, of course”: that final tagline fails to address the central difficulty about what the object of love is and so about love as a distinctly personal attitude. (Clausen 2019 might seem to address this worry by arguing that we love people not as having certain properties but rather as having “ organic unities ”: a holistic set of properties the value of each of which must be understood in essential part in terms of its place within that whole. Nonetheless, while this is an interesting and plausible way to think about the value of the properties of persons, that organic unity itself will be a (holistic) property held by the person, and it seems that the fundamental problem reemerges at the level of this holistic property: do we love the holistic unity rather than the person?)

The second worry concerns the fungibility of the object of love. To be fungible is to be replaceable by another relevantly similar object without any loss of value. Thus, money is fungible: I can give you two $5 bills in exchange for a $10 bill, and neither of us has lost anything. Is the object of love fungible? That is, can I simply switch from loving one person to loving another relevantly similar person without any loss? The worry about fungibility is commonly put this way: if we accept that love can be justified by appealing to properties of the beloved, then it may seem that in loving someone for certain reasons, I love him not simply as the individual he is, but as instantiating those properties. And this may imply that any other person instantiating those same properties would do just as well: my beloved would be fungible. Indeed, it may be that another person exhibits the properties that ground my love to a greater degree than my current beloved does, and so it may seem that in such a case I have reason to “trade up”—to switch my love to the new, better person. However, it seems clear that the objects of our loves are not fungible: love seems to involve a deeply personal commitment to a particular person, a commitment that is antithetical to the idea that our beloveds are fungible or to the idea that we ought to be willing to trade up when possible. [ 18 ]

In responding to these worries, Nozick (1989) appeals to the union view of love he endorses (see the section on Love as Union ):

The intention in love is to form a we and to identify with it as an extended self, to identify one’s fortunes in large part with its fortunes. A willingness to trade up, to destroy the very we you largely identify with, would then be a willingness to destroy your self in the form of your own extended self. [p. 78]

So it is because love involves forming a “we” that we must understand other persons and not properties to be the objects of love, and it is because my very identity as a person depends essentially on that “we” that it is not possible to substitute without loss one object of my love for another. However, Badhwar (2003) criticizes Nozick, saying that his response implies that once I love someone, I cannot abandon that love no matter who that person becomes; this, she says, “cannot be understood as love at all rather than addiction” (p. 61). [ 19 ]

Instead, Badhwar (1987) turns to her robust-concern account of love as a concern for the beloved for his sake rather than one’s own. Insofar as my love is disinterested — not a means to antecedent ends of my own—it would be senseless to think that my beloved could be replaced by someone who is able to satisfy my ends equally well or better. Consequently, my beloved is in this way irreplaceable. However, this is only a partial response to the worry about fungibility, as Badhwar herself seems to acknowledge. For the concern over fungibility arises not merely for those cases in which we think of love as justified instrumentally, but also for those cases in which the love is justified by the intrinsic value of the properties of my beloved. Confronted with cases like this, Badhwar (2003) concludes that the object of love is fungible after all (though she insists that it is very unlikely in practice). (Soble (1990, Chapter 13) draws similar conclusions.)

Nonetheless, Badhwar thinks that the object of love is “phenomenologically non-fungible” (2003, p. 63; see also 1987, p. 14). By this she means that we experience our beloveds to be irreplaceable: “loving and delighting in [one person] are not completely commensurate with loving and delighting in another” (1987, p. 14). Love can be such that we sometimes desire to be with this particular person whom we love, not another whom we also love, for our loves are qualitatively different. But why is this? It seems as though the typical reason I now want to spend time with Amy rather than Bob is, for example, that Amy is funny but Bob is not. I love Amy in part for her humor, and I love Bob for other reasons, and these qualitative differences between them is what makes them not fungible. However, this reply does not address the worry about the possibility of trading up: if Bob were to be at least as funny (charming, kind, etc.) as Amy, why shouldn’t I dump her and spend all my time with him?

A somewhat different approach is taken by Whiting (1991). In response to the first worry concerning the object of love, Whiting argues that Vlastos offers a false dichotomy: having affection for someone that is disinterested —for her sake rather than my own—essentially involves an appreciation of her excellences as such. Indeed, Whiting says, my appreciation of these as excellences, and so the underlying commitment I have to their value, just is a disinterested commitment to her because these excellences constitute her identity as the person she is. The person, therefore, really is the object of love. Delaney (1996) takes the complementary tack of distinguishing between the object of one’s love, which of course is the person, and the grounds of the love, which are her properties: to say, as Solomon does, that we love someone for reasons is not at all to say that we only love certain aspects of the person. In these terms, we might say that Whiting’s rejection of Vlastos’ dichotomy can be read as saying that what makes my attitude be one of disinterested affection—one of love—for the person is precisely that I am thereby responding to her excellences as the reasons for that affection. [ 20 ]

Of course, more needs to be said about what it is that makes a particular person be the object of love. Implicit in Whiting’s account is an understanding of the way in which the object of my love is determined in part by the history of interactions I have with her: it is she, and not merely her properties (which might be instantiated in many different people), that I want to be with; it is she, and not merely her properties, on whose behalf I am concerned when she suffers and whom I seek to comfort; etc. This addresses the first worry, but not the second worry about fungibility, for the question still remains whether she is the object of my love only as instantiating certain properties, and so whether or not I have reason to “trade up.”

To respond to the fungibility worry, Whiting and Delaney appeal explicitly to the historical relationship. [ 21 ] Thus, Whiting claims, although there may be a relatively large pool of people who have the kind of excellences of character that would justify my loving them, and so although there can be no answer to question (2) about why I come to love this rather than that person within this pool, once I have come to love this person and so have developed a historical relation with her, this history of concern justifies my continuing to love this person rather than someone else (1991, p. 7). Similarly, Delaney claims that love is grounded in “historical-relational properties” (1996, p. 346), so that I have reasons for continuing to love this person rather than switching allegiances and loving someone else. In each case, the appeal to both such historical relations and the excellences of character of my beloved is intended to provide an answer to question (3) , and this explains why the objects of love are not fungible.

There seems to be something very much right with this response. Relationships grounded in love are essentially personal, and it would be odd to think of what justifies that love to be merely non-relational properties of the beloved. Nonetheless, it is still unclear how the historical-relational propreties can provide any additional justification for subsequent concern beyond that which is already provided (as an answer to question (1) ) by appeal to the excellences of the beloved’s character (cf. Brink 1999). The mere fact that I have loved someone in the past does not seem to justify my continuing to love him in the future. When we imagine that he is going through a rough time and begins to lose the virtues justifying my initial love for him, why shouldn’t I dump him and instead come to love someone new having all of those virtues more fully? Intuitively (unless the change she undergoes makes her in some important sense no longer the same person he was), we think I should not dump him, but the appeal to the mere fact that I loved him in the past is surely not enough. Yet what historical-relational properties could do the trick? (For an interesting attempt at an answer, see Kolodny 2003 and also Howard 2019.)

If we think that love can be justified, then it may seem that the appeal to particular historical facts about a loving relationship to justify that love is inadequate, for such idiosyncratic and subjective properties might explain but cannot justify love. Rather, it may seem, justification in general requires appealing to universal, objective properties. But such properties are ones that others might share, which leads to the problem of fungibility. Consequently it may seem that love cannot be justified. In the face of this predicament, accounts of love that understand love to be an attitude towards value that is intermediate between appraisal and bestowal, between recognizing already existing value and creating that value (see Section 4.3 ) might seem to offer a way out. For once we reject the thought that the value of our beloveds must be either the precondition or the consequence of our love, we have room to acknowledge that the deeply personal, historically grounded, creative nature of love (central to bestowal accounts) and the understanding of love as responsive to valuable properties of the beloved that can justify that love (central to appraisal accounts) are not mutually exclusive (Helm 2010; Bagley 2015).

• Annas, J., 1977, “Plato and Aristotle on Friendship and Altruism”, Mind , 86: 532–54.
• Badhwar, N. K., 1987, “Friends as Ends in Themselves”, Philosophy & Phenomenological Research , 48: 1–23.
• –––, 2003, “Love”, in H. LaFollette (ed.), Practical Ethics , Oxford: Oxford University Press, 42–69.
• Badhwar, N. K. (ed.), 1993, Friendship: A Philosophical Reader , Ithaca, NY: Cornell University Press.
• Bagley, B., 2015, “Loving Someone in Particular”, Ethics , 125: 477–507.
• –––, 2018. “(The Varieties of) Love in Contemporary Anglophone Philosophy”, in Adrienne M. Martin (ed.), The Routledge Handbook of Love in Philosophy , New York, NY: Routledge, 453–64.
• Baier, A. C., 1991, “Unsafe Loves”, in Solomon & Higgins (1991), 433–50.
• Blum, L. A., 1980, Friendship, Altruism, and Morality , London: Routledge & Kegan Paul.
• –––, 1993, “Friendship as a Moral Phenomenon”, in Badhwar (1993), 192–210.
• Bransen, J., 2006, “Selfless Self-Love”, Ethical Theory and Moral Practice , 9: 3–25.
• Bratman, M. E., 1999, “Shared Intention”, in Faces of Intention: Selected Essays on Intention and Agency , Cambridge: Cambridge University Press, 109–29.
• Brentlinger, J., 1970/1989, “The Nature of Love”, in Soble (1989a), 136–48.
• Brink, D. O., 1999, “Eudaimonism, Love and Friendship, and Political Community”, Social Philosophy & Policy , 16: 252–289.
• Brown, R., 1987, Analyzing Love , Cambridge: Cambridge University Press.
• Clausen, G., 2019, “Love of Whole Persons”, The Journal of Ethics , 23 (4): 347–67.
• Cocking, D. & Kennett, J., 1998, “Friendship and the Self”, Ethics , 108: 502–27.
• Cooper, J. M., 1977, “Aristotle on the Forms of Friendship”, Review of Metaphysics , 30: 619–48.
• Delaney, N., 1996, “Romantic Love and Loving Commitment: Articulating a Modern Ideal”, American Philosophical Quarterly , 33: 375–405.
• Ebels-Duggan, K., 2008, “Against Beneficence: A Normative Account of Love”, Ethics , 119: 142–70.
• Fisher, M., 1990, Personal Love , London: Duckworth.
• Frankfurt, H., 1999, “Autonomy, Necessity, and Love”, in Necessity, Volition, and Love , Cambridge: Cambridge University Press, 129–41.
• Friedman, M. A., 1993, What Are Friends For? Feminist Perspectives on Personal Relationships and Moral Theory , Ithaca, NY: Cornell University Press.
• –––, 1998, “Romantic Love and Personal Autonomy”, Midwest Studies in Philosophy , 22: 162–81.
• Gilbert, M., 1989, On Social Facts , Princeton, NJ: Princeton University Press.
• –––, 1996, Living Together: Rationality, Sociality, and Obligation , Rowman & Littlefield.
• –––, 2000, Sociality and Responsibility: New Essays in Plural Subject Theory , Lanham, MD: Rowman & Littlefield.
• Grau, C. & Smuts, A., 2017, Oxford Handbook of the Philosophy of Love , Oxford: Oxford University Press.
• Hamlyn, D. W., 1989, “The Phenomena of Love and Hate”, in Soble (1989a), 218–234.
• Han, Y., 2021, “Do We Love for Reasons?”, Philosophy & Phenomenological Research , 102: 106–126.
• Hegel, G. W. F., 1997, “A Fragment on Love”, in Solomon & Higgins (1991), 117–20.
• Helm, B. W., 2008, “Plural Agents”, Noûs , 42: 17–49.
• –––, 2009, “Love, Identification, and the Emotions”, American Philosophical Quarterly , 46: 39–59.
• –––, 2010, Love, Friendship, and the Self: Intimacy, Identification, and the Social Nature of Persons , Oxford: Oxford University Press.
• Howard, C., 2019, “Fitting Love and Reasons for Loving” in M. Timmons (ed.), Oxford Studies in Normative Ethics (Volume 9). doi:10.1093/oso/9780198846253.001.0001
• Jaworska, A. & Wonderly, M., 2017, “Love and Caring”, in C. Grau & A. Smuts (2020). doi:10.1093/oxfordhb/9780199395729.013.15
• Jollimore, T, 2011, Love’s Vision , Princeton, NJ: Princeton University Press.
• Kolodny, N., 2003, “Love as Valuing a Relationship”, The Philosophical Review , 112: 135–89.
• Kraut, Robert, 1986 “Love De Re ”, Midwest Studies in Philosophy , 10: 413–30.
• LaFollette, H., 1996, Personal Relationships: Love, Identity, and Morality , Cambridge, MA: Blackwell Press.
• Lamb, R. E., (ed.), 1997, Love Analyzed , Westview Press.
• Liddell, H. G., Scott, R., Jones, H. S., & McKenzie, R., 1940, A Greek-English Lexicon , Oxford: Clarendon Press, 9th edition.
• Martin, A., 2015, “Love, Incorporated”, Ethical Theory and Moral Practice , 18: 691–702.
• Montaigne, M., [E], Essays , in The Complete Essays of Montaigne , Donald Frame (trans.), Stanford: Stanford University Press, 1958.
• Naar, H., 2013, “A Dispositional Theory of Love”, Pacific Philosophical Quarterly , 94(3): 342–357.
• Newton-Smith, W., 1989, “A Conceptual Investigation of Love”, in Soble (1989a), 199–217.
• Nozick, R., 1989, “Love’s Bond”, in The Examined Life: Philosophical Meditations , New York: Simon & Schuster, 68–86.
• Nussbaum, M., 1990, “Love and the Individual: Romantic Rightness and Platonic Aspiration”, in Love’s Knowledge: Essays on Philosophy and Literature , Oxford: Oxford University Press, 314–34.
• Nygren, A., 1953a, Agape and Eros , Philadelphia, PA: Westminster Press.
• –––, 1953b, “ Agape and Eros ”, in Soble (1989a), 85–95.
• Ortiz-Millán, G., 2007, “Love and Rationality: On Some Possible Rational Effects of Love”, Kriterion , 48: 127–44.
• Pismenny, A. & Prinz, J., 2017, “Is Love an Emotion?”, in C. Grau & A. Smuts (2017). doi:10.1093/oxfordhb/9780199395729.013.10
• Price, A. W., 1989, Love and Friendship in Plato and Arisotle , New York: Clarendon Press.
• Rorty, A. O., 1980, “Introduction”, in A. O. Rorty (ed.), Explaining Emotions , Berkeley: University of California Press, 1–8.
• –––, 1986/1993, “The Historicity of Psychological Attitudes: Love is Not Love Which Alters Not When It Alteration Finds”, in Badhwar (1993), 73–88.
• Scruton, R., 1986, Sexual Desire: A Moral Philosophy of the Erotic , New York: Free Press.
• Searle, J. R., 1990, “Collective Intentions and Actions”, in P. R. Cohen, M. E. Pollack, & J. L. Morgan (eds.), Intentions in Communication , Cambridge, MA: MIT Press, 401–15.
• Setiya, K., 2014, “Love and the Value of a Life”, Philosophical Review , 123: 251–80.
• Sherman, N., 1993, “Aristotle on the Shared Life”, in Badhwar (1993), 91–107.
• Singer, I., 1984a, The Nature of Love, Volume 1: Plato to Luther , Chicago: University of Chicago Press, 2nd edition.
• –––, 1984b, The Nature of Love, Volume 2: Courtly and Romantic , Chicago: University of Chicago Press.
• –––, 1989, The Nature of Love, Volume 3: The Modern World , Chicago: University of Chicago Press, 2nd edn.
• –––, 1991, “From The Nature of Love ”, in Solomon & Higgins (1991), 259–78.
• –––, 1994, The Pursuit of Love , Baltimore, MD: Johns Hopkins University Press.
• –––, 2009, Philosophy of Love: A Partial Summing-up , Cambridge, MA: MIT Press.
• Soble, A. (ed.), 1989a, Eros, Agape, and Philia: Readings in the Philosophy of Love , New York, NY: Paragon House.
• –––, 1989b, “An Introduction to the Philosophy of Love”, in Soble (1989a), xi-xxv.
• –––, 1990, The Structure of Love , New Haven: Yale University Press.
• –––, 1997, “Union, Autonomy, and Concern”, in Lamb (1997), 65–92.
• Solomon, R. C., 1976, The Passions , New York: Anchor Press.
• –––, 1981, Love: Emotion, Myth, and Metaphor , New York: Anchor Press.
• –––, 1988, About Love: Reinventing Romance for Our Times , New York: Simon & Schuster.
• Solomon, R. C. & Higgins, K. M. (eds.), 1991, The Philosophy of (Erotic) Love , Lawrence: Kansas University Press.
• Stump, E., 2006, “Love by All Accounts”, Presidential Address to the Central APA, Proceedings and Addresses of the American Philosophical Association , 80: 25–43.
• Taylor, G., 1976, “Love”, Proceedings of the Aristotelian Society , 76: 147–64.
• Telfer, E., 1970–71, “Friendship”, Proceedings of the Aristotelian Society , 71: 223–41.
• Thomas, L., 1987, “Friendship”, Synthese , 72: 217–36.
• –––, 1989, “Friends and Lovers”, in G. Graham & H. La Follette (eds.), Person to Person , Philadelphia, PA: Temple University Press, 182–98.
• –––, 1991, “Reasons for Loving”, in Solomon & Higgins (1991), 467–476.
• –––, 1993, “Friendship and Other Loves”, in Badhwar (1993), 48–64.
• Tuomela, R., 1984, A Theory of Social Action , Dordrecht: Reidel.
• –––, 1995, The Importance of Us: A Philosophical Study of Basic Social Notions , Stanford, CA: Stanford University Press.
• Velleman, J. D., 1999, “Love as a Moral Emotion”, Ethics , 109: 338–74.
• –––, 2008, “Beyond Price”, Ethics , 118: 191–212.
• Vlastos, G., 1981, “The Individual as Object of Love in Plato”, in Platonic Studies , 2nd edition, Princeton, NJ: Princeton University Press, 3–42.
• White, R. J., 2001, Love’s Philosophy , Rowman & Littlefield.
• Whiting, J. E., 1991, “Impersonal Friends”, Monist , 74: 3–29.
• –––, 2013, “Love: Self-Propagation, Self-Preservation, or Ekstasis?”, Canadian Journal of Philosophy , 43: 403–29.
• Willigenburg, T. Van, 2005, “Reason and Love: A Non-Reductive Analysis of the Normativity of Agent-Relative Reasons”, Ethical Theory and Moral Practice , 8: 45–62.
• Wollheim, R., 1984, The Thread of Life , Cambridge, MA: Harvard University Press.
• Wonderly, M., 2016, “On Being Attached”, Philosophical Studies , 173: 223–42.
• –––, 2017, “Love and Attachment”, American Philosophical Quarterly , 54: 235–50.

How to cite this entry . Preview the PDF version of this entry at the Friends of the SEP Society . Look up topics and thinkers related to this entry at the Internet Philosophy Ontology Project (InPhO). Enhanced bibliography for this entry at PhilPapers , with links to its database.

• Aristotle , Nicomachean Ethics , translated by W.D. Ross.
• Moseley, A., “ Philosophy of Love ,” in J. Fieser (ed.), Internet Encyclopedia of Philosophy

character, moral | emotion | friendship | impartiality | obligations: special | personal identity | Plato: ethics | Plato: rhetoric and poetry | respect | value: intrinsic vs. extrinsic

Copyright © 2021 by Bennett Helm < bennett . helm @ fandm . edu >

• Accessibility

Support SEP

Mirror sites.

View this site from another server:

• Info about mirror sites

The Stanford Encyclopedia of Philosophy is copyright © 2024 by The Metaphysics Research Lab , Department of Philosophy, Stanford University

Library of Congress Catalog Data: ISSN 1095-5054

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings

Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now .

• Advanced Search
• Journal List
• Front Psychol

Proximate and Ultimate Perspectives on Romantic Love

Associated data.

Romantic love is a phenomenon of immense interest to the general public as well as to scholars in several disciplines. It is known to be present in almost all human societies and has been studied from a number of perspectives. In this integrative review, we bring together what is known about romantic love using Tinbergen’s “four questions” framework originating from evolutionary biology. Under the first question, related to mechanisms, we show that it is caused by social, psychological mate choice, genetic, neural, and endocrine mechanisms. The mechanisms regulating psychopathology, cognitive biases, and animal models provide further insights into the mechanisms that regulate romantic love. Under the second question, related to development, we show that romantic love exists across the human lifespan in both sexes. We summarize what is known about its development and the internal and external factors that influence it. We consider cross-cultural perspectives and raise the issue of evolutionary mismatch. Under the third question, related to function, we discuss the fitness-relevant benefits and costs of romantic love with reference to mate choice, courtship, sex, and pair-bonding. We outline three possible selective pressures and contend that romantic love is a suite of adaptions and by-products. Under the fourth question, related to phylogeny, we summarize theories of romantic love’s evolutionary history and show that romantic love probably evolved in concert with pair-bonds in our recent ancestors. We describe the mammalian antecedents to romantic love and the contribution of genes and culture to the expression of modern romantic love. We advance four potential scenarios for the evolution of romantic love. We conclude by summarizing what Tinbergen’s four questions tell us, highlighting outstanding questions as avenues of potential future research, and suggesting a novel ethologically informed working definition to accommodate the multi-faceted understanding of romantic love advanced in this review.

Introduction

Romantic love is a complex suite of adaptations and by-products that serves a range of functions related to reproduction ( Fletcher et al., 2015 ; Buss, 2019 ). It often occurs early in a romantic relationship but can lead to long-term mating. It is a universal or near-universal ( Jankowiak and Fischer, 1992 ; Gottschall and Nordlund, 2006 ; Jankowiak and Paladino, 2008 ; Fletcher et al., 2015 ; Buss, 2019 ; Sorokowski et al., 2020 ) and is characterized by a range of cognitive, emotional, behavioral, social, genetic, neural, and endocrine activity. It occurs across the lifespan in both sexes. Romantic love serves a variety of functions that vary according to life-stage and duration, including mate choice, courtship, sex, and pair-bonding. Its evolutionary history is probably coupled with the emergence of pair-bonds relatively recently in human evolutionary history.

Romantic love has received attention from scholars in diverse fields, including neurobiology, endocrinology, psychology, and anthropology. Our review aims to synthesize multiple threads of knowledge into a more well-rounded perspective on romantic love. To accomplish this, we do the following: First, we lay out our analytical framework based on Tinbergen’s (1963) “four questions” for explaining a biological phenomenon. Second, using this framework as an organizing tool, we summarize what is known about the social mechanisms, psychological mate choice mechanisms, genetics, neurobiology, endocrinology, development across the lifetime of an individual, fitness-relevant functions, and evolutionary history of romantic love. Finally, we conclude by summarizing what Tinbergen’s four questions tell us, identifying areas for future research, and providing a new ethologically informed working definition of romantic love.

Analytical Framework

Much work has been done to examine romantic love as a biological characteristic. Numerous reviews have described the neurobiology and endocrinology of romantic love (e.g., Fisher, 2004 , 2006 ; Zeki, 2007 ; Hatfield and Rapson, 2009 ; Reynaud et al., 2010 ; Cacioppo et al., 2012b ; de Boer et al., 2012 ; Diamond and Dickenson, 2012 ; Dunbar, 2012 ; Tarlaci, 2012 ; Xu et al., 2015 ; Fisher et al., 2016 ; Zou et al., 2016 ; Tomlinson et al., 2018 ; Walum and Young, 2018 ; Cacioppo, 2019 ). Two meta-analyses ( Ortigue et al., 2010 ; Cacioppo et al., 2012a ) considered fMRI studies of romantic love. There have been some accounts of romantic love or love from an evolutionary perspective (e.g., Hendrick and Hendrick, 1991 ; Fisher, 1995 , 2016 ; Fisher et al., 2006 , 2016 ; Kenrick, 2006 ; Lieberman and Hatfield, 2006 ; Schmitt, 2006 ; Fletcher et al., 2015 ; Sorokowski et al., 2017 ; Buss, 2019 ).

No one, however, has addressed the full spectrum of approaches used in biology to provide a comprehensive account of romantic love. We fill this gap by framing our review of romantic love around Tinbergen’s (1963) “four questions” for explaining biological traits. It was developed in the context of trying to provide a holistic, integrative understanding of animal behavior, and is an extension of earlier explanatory frameworks, including Mayr’s (1961) distinction between proximate and ultimate explanations in biology ( Bateson and Laland, 2013 ). It includes two proximate explanations, mechanistic and ontogenetic, and two ultimate (evolutionary) explanations, functional and phylogenetic. To illustrate the use of this framework, we refer to elements of Zeifman’s (2001) analysis of infant crying as a biological trait using this framework. An outline of our use of this framework is presented in Table 1 .

Summary of romantic love using Tinbergen’s (1963) framework.

Proximate explanations focus on the workings of biological and social systems and their components, both on a short-term (mechanistic) and longer-term (ontogenetic) basis ( Tinbergen, 1963 ; Zeifman, 2001 ). Mechanistic explanations attempt to answer questions about how behavior is produced by an organism. It is about the immediate causation of the behavior. A baby’s cry, under this class of explanation, might be viewed as an expression of emotion regulated by the limbic system. In our analysis, we ask: “What are the mechanisms that cause romantic love?” Ontogenetic explanations attempt to answer questions about how the behavior develops over the life course. A baby’s cry, thus, might be viewed as a vocalization that changes in frequency and context over the first year of life, and then across the rest of childhood. In our analysis, we ask: “How does romantic love develop over the lifetime of an individual?”

Ultimate explanations focus on the application of evolutionary logic to understand behavior, both on a short-term (functional) and long-term (phylogenetic) basis ( Tinbergen, 1963 ; Zeifman, 2001 ). Functional explanations attempt to answer questions about the fitness consequences of behavior and how it functions as an adaptation. A baby’s cry, thus, might be viewed as an adaptation that enhances offspring survival by eliciting care or providing information about its state. As the fitness consequences may be negative as well, it might focus on both benefits and costs. For instance, the cry may decrease survival by attracting predators or depleting scarce energy reserves. In our analysis, we ask: “What are the fitness-relevant functions of romantic love?” Phylogenetic explanations attempt to answer questions about the evolutionary history of a behavior and the mechanisms that produce it. A baby’s cry, thus, might be understood from the perspective of whether similar behaviors are present in closely related species. In our analysis, we ask: “What is the evolutionary history of romantic love?”

Tinbergen’s (1963) framework has been a useful tool for organizing research and theory on behavior and other biological traits across all major kingdoms of life, from plants (e.g., Satake, 2018 ) to humans (e.g., Winterhalder and Smith, 1992 ; Zeifman, 2001 ; Stephen et al., 2017 ; Luoto et al., 2019 ). It allows us to build holistic explanations of biological phenomena by examining complementary, but often non-mutually exclusive, categories of explanation ( Bateson and Laland, 2013 ). We believe that this approach to understanding romantic love will clarify the usefulness and interdependence of the various aspects of the biology of romantic love without falling into the pitfalls of posing explanations for the phenomena that are in opposition rather than complementary ( Nesse, 2013 ).

Definitions

There are a number of definitions and descriptions of romantic love. These definitions and descriptions have different names for romantic love, but all are attempting to define the same construct. We present, here, four definitions or descriptions of romantic love that continue to have relevance to contemporary research.

Walster and Walster (1978) were among the first to scientifically define romantic love. They gave it the name “passionate love” and their definition has been revised several times (e.g., Hatfield and Walster, 1985 ; Hatfield and Rapson, 1993 ). A definition of passionate love is:

A state of intense longing for union with another. Passionate love is a complex functional whole including appraisals or appreciations, subjective feelings, expressions, patterned physiological processes, action tendencies, and instrumental behaviors. Reciprocated love (union with the other) is associated with fulfillment and ecstasy; unrequited love (separation) with emptiness, anxiety, or despair ( Hatfield and Rapson, 1993 , p. 5).

Hendrick and Hendrick (1986) propose a description of romantic love in the context of describing six different “love styles” ( Lee, 1976 ). They label it “eros.” It too has undergone some changes. A recent version of the description is:

Strong physical attraction, emotional intensity, a preferred physical appearance, and a sense of inevitability of the relationship define the central core of eros. Eros can “strike” suddenly in a revolution of feeling and thinking ( Hendrick and Hendrick, 2019 , p. 244).

Sternberg (1986) provides a description of romantic love based on three components of love in close relationships: intimacy, passion and commitment. He calls it “romantic love” and describes it as such:

This kind of love derives from a combination of the intimacy and passion components of love. In essence, it is liking with an added element, namely, the arousal brought about by physical attraction and its concomitants. According to this view, then, romantic lovers are not only drawn physically to each other but are also bonded emotionally ( Sternberg, 1986 , p. 124).

A more recent definition of romantic love informed by evolutionary theory has been proposed by Fletcher et al. (2015) . Rather than providing a discrete series of sentences, they propose a working definition of “romantic love” that is explained with reference to some of the psychological research on romantic love and by summarizing five distinct features of romantic love. These features are:

• (1) Romantic love is a powerful commitment device, composed of passion, intimacy, and caregiving;
• (2) Romantic love is universal and is associated with pair-bonding across cultures;
• (3) Romantic love automatically suppresses effort and attention given to alternative partners;
• (4) Romantic love has distinct emotional, behavioral, hormonal, and neuropsychological features; and
• (5) Successful pair-bonding predicts better health and survival across cultures for both adults and offspring ( Fletcher et al., 2015 , p. 22).

Despite these attempts to define and describe romantic love, no single term or definition has been universally adopted in the literature. The psychological literature often uses the terms “romantic love,” “love,” and “passionate love” (e.g., Sternberg and Sternberg, 2019 ). Seminal work called it “limerence” ( Tennov, 1979 ). The biological literature generally uses the term “romantic love” and has investigated “early stage intense romantic love” (e.g., Xu et al., 2011 ), “long-term intense romantic love” (e.g., Acevedo et al., 2012 ), or being “in love” (e.g., Marazziti and Canale, 2004 ). In this review, what we term “romantic love” encompasses all of these definitions, descriptions, and terms. Romantic love contrasts with “companionate love,” which is felt less intensely, often follows a period of romantic love ( Hatfield and Walster, 1985 ), and merges feelings of intimacy and commitment ( Sternberg, 1986 ).

Psychological Characteristics

Hatfield and Sprecher (1986) theoretically developed the Passionate Love Scale to assess the cognitive, emotional, and behavioral components of romantic love among people who are in a relationship. There are other ways of measuring romantic love ( Hatfield et al., 2012 ), and some, such as Sternberg’s Triangular Love Scale ( Sternberg, 1997 ; Sumter et al., 2013 ) or the Love Attitudes Scale ( Hendrick and Hendrick, 1986 ; Hendrick et al., 1998 ), measure the same constructs ( Masuda, 2003 ; Graham, 2011 ). The Passionate Love Scale is only valid in people who are in a romantic relationship with their loved one. Regardless, the Passionate Love Scale provides a particularly useful account of some of the psychological characteristics of romantic love. It has been used widely in research investigating romantic love in relationships ( Feybesse and Hatfield, 2019 ).

Cognitive components of romantic love include intrusive thinking or preoccupation with the partner, idealization of the other in the relationship, and desire to know the other and to be known. Emotional components include attraction to the other, especially sexual attraction, negative feelings when things go awry, longing for reciprocity, desire for complete union, and physiological arousal. Behavioral components include actions toward determining the other’s feelings, studying the other person, service to the other, and maintaining physical closeness ( Hatfield and Sprecher, 1986 ).

Romantic love shares a number of physiological and psychological characteristics with addiction. “[T]hey focus on their beloved (salience); and they yearn for their beloved (craving). They feel a “rush” of exhilaration when seeing or thinking about him or her (euphoria/intoxication). As their relationship builds, the lover experiences the common signs of drug withdrawal, too, including protest, crying spells, lethargy, anxiety, insomnia, or hypersomnia, loss of appetite or binge eating, irritability and chronic loneliness.” ( Fisher et al., 2016 , p. 2) A number of reviews have highlighted the behavioral and neurobiological similarities between addiction and romantic love (e.g., Reynaud et al., 2010 ; Fisher et al., 2016 ; Zou et al., 2016 ).

There is evidence that romantic love is associated with increased hypomanic symptoms (elevated mood, Brand et al., 2007 ; Bajoghli et al., 2011 , 2013 , 2014 , 2017 ; Brand et al., 2015 ), a change (increase or decrease) in depression symptoms ( Stoessel et al., 2011 ; Bajoghli et al., 2013 , 2014 , 2017 ; Price et al., 2016 ; Verhallen et al., 2019 ; Kuula et al., 2020 ), and increased state anxiety ( Hatfield et al., 1989 ; Wang and Nguyen, 1995 ; Bajoghli et al., 2013 , 2014 , 2017 ; Brand et al., 2015 ; Kuula et al., 2020 ). See Supplementary Table 1 for information about studies investigating hypomania, depression, and anxiety symptoms in people experiencing romantic love. Romantic love is also characterized by cognitive biases which resemble “positive illusions,” which are a tendency to perceive one’s relationship and one’s loved one in a positive light or bias ( Song et al., 2019 ).

Proximate Perspectives

When applied to romantic love, the first of Tinbergen’s (1963) four questions asks: “What are the mechanisms that cause romantic love?” This can be answered with reference to social mechanisms, psychological mate choice mechanisms, genetics, neurobiology, and endocrinology ( Zeifman, 2001 ; Bateson and Laland, 2013 ). Research into the social mechanisms and genetics of romantic love are in their infancy, but there is substantial theory on psychological mate choice mechanisms and ample research has been undertaken into the neural and endocrine activity associated with romantic love. Additional insights can be garnered from the neurobiology and endocrinology of psychopathology, cognitive biases, and animal models.

Social Mechanisms

Some precursors to romantic love (others discussed below) that act strongly as social mechanisms that cause romantic love are reciprocal liking, propinquity, social influence, and the filling of needs (e.g., Aron et al., 1989 ; Pines, 2001 ; Riela et al., 2010 ). Reciprocal liking (mutual attraction) is “being liked by the other, both in general, as well as when it is expressed through self-disclosure” ( Aron et al., 1989 , p. 245). It has been frequently identified as preceding romantic love among participants from the United States and is cross-culturally identified as the strongest preference in mates among both sexes ( Buss et al., 1990 ). “Whether expressed in a warm smile or a prolonged gaze, the message is unmistakable: ‘It’s safe to approach, I like you too. I’ll be nice. You’re not in danger of being rejected”’ ( Hazan and Diamond, 2000 , p. 197). Reciprocal liking may encourage the social approach and courtship activities characteristic and causative of romantic love.

Propinquity is “familiarity, in terms of having spent time together, living near the other, mere exposure to the other, thinking about the other, or anticipating interaction with the other” ( Aron et al., 1989 , p. 245). It has more recently been named “familiarity” (see Riela et al., 2010 ). The extended exposure of an individual to another helps to cause romantic love and specifically facilities the development of romantic love over extended periods of time. Propinquity, in our evolutionary history, served to ensure that “potential mates who are encountered daily at the river’s edge have an advantage over those residing on the other side” ( Hazan and Diamond, 2000 , p. 201). Given that the pool of potential mates in our evolutionary history would have been limited by the size of the groups in which we lived and the fact that most individuals of reproductive age would already have been involved in long-term mating relationships, propinquity is likely to have played a particularly important role in the generation of romantic love. Until recently (to a somewhat lesser extent, today), with the wide-scale take-up of online dating, propinquity played a role in the formation of many long-term pair-bonds, and presumably, romantic love, as is evidenced by a relatively high proportion of people having met their romantic partners in the places where exposure was facilitated, such as school, college, or work ( Rosenfeld et al., 2019 ). Changes in the importance of certain precursors in causing romantic love may be the result of a mismatch between the modern environment and our genotypes that evolved in a very different environment (discussed in detail below; see Li et al., 2018 ).

Social influences are “both general social norms and approval of others in the social network” ( Aron et al., 1989 , p. 245). This may cause people to fall in love with others who are of a similar attractiveness, cultural group, ethnic group, profession, economic class, or who are members of the same social group. Social influences may, directly, impact who we fall in love with by providing approval to a romantic union or, indirectly, by facilitating propinquity. The effect of social influences is demonstrated in the relatively large number of people who met their romantic partner through friends ( Rosenfeld et al., 2019 ). The filling of needs is “having the self’s needs met or meeting the needs of the other (e.g., he makes me happy, she buys me little presents that show she cares), and typically implies characteristics that are highly valued and beneficial in relationship maintenance (e.g., compassion, respect)” ( Riela et al., 2010 , pp. 474–475). The filling of needs may cause romantic love when social interaction facilitates a union where both partners complement each other.

Psychological Mate Choice Mechanisms

Mate choice, in the fields of evolutionary theory, can be defined as “the process that occurs whenever the effects of traits expressed in one sex lead to non-random allocation of reproductive investment with members of the opposite sex” ( Edward, 2015 , p. 301). It is essentially the process of intersexual selection proposed by Darwin (2013) more than 150 years ago ( Darwin, 1859 ) whereby someone has a preference for mating with a particular individual because of that individual’s characteristics. Mate choice, to that extent, involves the identification of a desirable conspecific ( Fisher et al., 2005 ) and sometimes, the focusing of mating energies on that individual. Mate preferences, sexual desire, and attraction all contribute to romantic love. The concepts of “extended phenotypes” and “overall attractiveness” help to explain how these features operate. Romantic love, as discussed below, serves a mate choice function ( Fisher et al., 2005 ) and these mechanisms and constructs contribute to when, and with whom, an individual falls in love.

A large body of research has developed around universal mate preferences (e.g., Buss and Barnes, 1986 ; Buss, 1989 ; Buss et al., 1990 ; Buss and Schmitt, 2019 ; Walter et al., 2020 ). Women, more than men, show a strong preference for resource potential, social status, a slightly older age, ambition and industriousness, dependability and stability, intelligence, compatibility, certain physical indicators, signs of good health, symmetry, masculinity, love, kindness, and commitment ( Buss, 1989 , 2016 ; Walter et al., 2020 ). Men, more than women, have preferences for youth, physical beauty, certain body shapes, chastity, and fidelity ( Buss, 1989 , 2016 ). Both sexes have particularly strong preferences for kindness and intelligence ( Buss et al., 1990 ). A male-taller-than-female norm exists in mate preferences and there is some evidence that women have a preference for taller-than-average height (e.g., Salska et al., 2008 ; Yancey and Emerson, 2014 ). Mutual attraction and reciprocated love are the most important characteristics that both women and men look for in a potential partner ( Buss et al., 1990 ).

Mate choice and attraction may be based on assessments of “extended phenotypes” ( Dawkins, 1982 ; Luoto, 2019a ), which include biotic and abiotic features of the environment that are influenced by an individual’s genes. For example, an extended phenotype would include an individual’s dwelling, car, pets, and social media presence. These can convey information relevant to fitness. Overall mate attractiveness, which is constituted by signs of health and fertility, neurophysiological efficiency, provisioning ability and resources, and capacity for cooperative relationships ( Miller and Todd, 1998 ) may be another heuristic through which attraction and mate choice operate.

Many mate preferences are relatively universal and therefore are likely to have at least some genetic basis (as suggested by, Sugiyama, 2015 ). While mate preferences are linked to actual mate selection ( Li et al., 2013 ; Li and Meltzer, 2015 ; Conroy-Beam and Buss, 2016 ; Buss and Schmitt, 2019 ), strong mate preferences do not always translate into real-world mate choice ( Todd et al., 2007 ; Stulp et al., 2013 ). This is in part because mate preferences function in a tradeoff manner whereby some preferences are given priority over others (see Li et al., 2002 ; Thomas et al., 2020 ). That is, mate choice is a multivariate process that includes the integration and tradeoff of several preferences ( Conroy-Beam et al., 2016 ). Mate preferences are important because they may serve as a means of screening potential mates, while sexual desire and attraction operationalize these preferences, and romantic love crystalizes them.

Sexual desire and attraction may be antecedents to falling in love and there is evidence that physiologically, sexual desire progresses into romantic love within shared neural structures ( Cacioppo et al., 2012a ). However, although both sexual desire and attraction operationalize mate choice, only attraction, and not sexual desire, may be necessary for romantic love to occur (see Leckman and Mayes, 1999 ; Diamond, 2004 ). Intense attraction is characterized by increased energy, focused attention, feelings of exhilaration, intrusive thinking, and a craving for emotional union ( Fisher, 1998 ) although it exists on a spectrum of intensity.

Changes in the expression of at least 61 genes are associated with falling in love in women ( Murray et al., 2019 ) suggesting that these genes may regulate features of romantic love. The DRD2 Taq I A polymorphism, which regulates Dopamine 2 receptor density ( Jonsson et al., 1999 ), is associated with eros ( Emanuele et al., 2007 ). Polymorphisms of genes that regulate vasopressin receptors (AVPR1a rs3), oxytocin receptors (OXTR rs53576), dopamine 4 receptors (DRD4-7R), and dopamine transmission (COMT rs4680) are associated with activity in the ventral tegmental area which, in turn, is associated with eros in newlyweds ( Acevedo et al., 2020 ).

Neurobiology

Neuroimaging studies (see Supplementary Table 2 ) implicate dozens of brain regions in romantic love. We focus, here, on only some of the most frequently replicated findings in an attempt to simplify a description of the neural activity associated with romantic love and explain its psychological characteristics. Romantic love, at least in people who are in a relationship with their loved one, appears to be associated with activity (activation or deactivation compared with a control condition) in four main overlapping systems: reward and motivation, emotions, sexual desire and arousal, and social cognition.

Reward and motivation structures associated with romantic love include those found in the mesolimbic pathway: the ventral tegmental area, nucleus accumbens, amygdala, and medial prefrontal cortex ( Xu et al., 2015 ). Activity in the mesolimbic pathway substantiates the claim that romantic love is a motivational state ( Fisher et al., 2005 ) and helps to explain why romantic love is characterized by psychological features such as longing for reciprocity, desire for complete union, service to the other, maintaining physical closeness, and physiological arousal ( Hatfield and Sprecher, 1986 ).

Emotional centers of the brain associated with romantic love include the amygdala, the anterior cingulate cortex ( Bartels and Zeki, 2000 ; Aron et al., 2005 ; Fisher et al., 2010 ; Younger et al., 2010 ; Zeki and Romaya, 2010 ; Stoessel et al., 2011 ; Acevedo et al., 2012 ; Scheele et al., 2013 ; Song et al., 2015 ), and the insula ( Bartels and Zeki, 2000 ; Aron et al., 2005 ; Ortigue et al., 2007 ; Fisher et al., 2010 ; Younger et al., 2010 ; Zeki and Romaya, 2010 ; Stoessel et al., 2011 ; Acevedo et al., 2012 ; Xu et al., 2012b ; Song et al., 2015 ). Activity in these structures helps to explain romantic love’s emotional features such as negative feelings when things go awry, longing for reciprocity, desire for complete union, and physiological arousal ( Hatfield and Sprecher, 1986 ).

The primary areas associated with both romantic love and sexual desire and arousal include the caudate, insula, putamen, and anterior cingulate cortex ( Diamond and Dickenson, 2012 ). The involvement of these regions helps to explain why people experiencing romantic love feel extremely sexually attracted to their loved one ( Hatfield and Sprecher, 1986 ). The neural similarities and overlapping psychological characteristics of romantic love and sexual desire are well documented (see Hatfield and Rapson, 2009 ; Cacioppo et al., 2012a ; Diamond and Dickenson, 2012 ).

Social cognition centers in the brain repeatedly associated with romantic love include the amygdala, the insula ( Adolphs, 2001 ), and the medial prefrontal cortex ( Van Overwalle, 2009 ). Social cognition plays a role in the social appraisals and cooperation characteristics of romantic love. Activity in these regions helps to explain psychological characteristics such as actions toward determining the other’s feelings, studying the other person, and service to the other ( Hatfield and Sprecher, 1986 ).

In addition to activity in these four systems, romantic love is associated with activity in higher-order cortical brain areas that are involved in attention, memory, mental associations, and self-representation ( Cacioppo et al., 2012b ). Mate choice (a function of romantic love detailed below) has been specifically associated with the mesolimbic pathway and hypothalamus ( Calabrò et al., 2019 ). The mesolimbic pathway, thalamus, hypothalamus, amygdala, septal region, prefrontal cortex, cingulate cortex, and insula have been specifically associated with human sexual behavior ( Calabrò et al., 2019 ), which has implications for the sex function of romantic love (detailed below).

Isolated studies have identified sex differences in the neurobiological activity associated with romantic love. One study ( Bartels and Zeki, 2004 ) found activity in the region ventral to the genu in only women experiencing romantic love. One preliminary study of romantic love (see Fisher et al., 2006 ) found that “[m]en tended to show more activity than women in a region of the right posterior dorsal insula that has been correlated with penile turgidity and male viewing of beautiful faces. Men also showed more activity in regions associated with the integration of visual stimuli. Women tended to show more activity than men in regions associated with attention, memory and emotion” (p. 2181).

Endocrinology

Romantic love is associated with changes in circulating sex hormones, serotonin, dopamine, oxytocin, cortisol, and nerve growth factor systems. Table 2 presents the endocrine factors which are found to be different, compared to controls, in people experiencing romantic love. More information about the controlled studies discussed in this subsection is presented in Supplementary Table 3 . Endocrine factors associated with romantic love have most of their psychological and other effects because of their role as a hormone (e.g., sex hormones, cortisol) or neurotransmitter (e.g., serotonin, dopamine), although many factors operate as both (see Calisi and Saldanha, 2015 ) or as neurohormones.

Significant results of controlled endocrine studies investigating romantic love.

Romantic love is associated with changes in the sex hormones testosterone, follicle-stimulating hormone, and luteinizing hormone ( Marazziti and Canale, 2004 ; Durdiakova et al., 2017 ; Sorokowski et al., 2019 ), although the findings have been inconsistent. Testosterone appears to be lower in men experiencing romantic love than controls ( Marazziti and Canale, 2004 ) and higher eros scores are associated with lower levels of testosterone in men ( Durdiakova et al., 2017 ). Lower levels of testosterone in fathers are associated with greater involvement in parenting (see Storey et al., 2020 , for review). The direction of testosterone change in women is unclear (see Marazziti and Canale, 2004 ; Sorokowski et al., 2019 ). Sex hormones are involved in the establishment and maintenance of sexual characteristics, sexual behavior, and reproductive function ( Mooradian et al., 1987 ; Chappel and Howles, 1991 ; Holloway and Wylie, 2015 ). Some sex hormones can influence behavior through their organizing effects resulting from prenatal and postnatal exposure. In the case of romantic love, however, the effects of sex hormones on the features of romantic love are the result of activating effects associated with behaviorally contemporaneous activity. It is possible that sex hormones influence individual differences in the presentation of romantic love through their organizing effect (see Motta-Mena and Puts, 2017 ; Luoto et al., 2019 ; Arnold, 2020 ; McCarthy, 2020 , for descriptions of organizing and activating effects of testosterone, estradiol, and progesterone). Changes in sex hormones could help to explain the increase in sexual desire and arousal associated with romantic love ( Hatfield and Sprecher, 1986 ; Hatfield and Rapson, 2009 ; Diamond and Dickenson, 2012 ).

Romantic love is associated with decreased serotonin transporter density ( Marazziti et al., 1999 ) and changes in plasma serotonin ( Langeslag et al., 2012 ), although inconsistencies have been found in the direction of change according to sex. In one study, men experiencing romantic love displayed lower serotonin levels than controls and women displayed higher serotonin levels than controls ( Langeslag et al., 2012 ). Decreased serotonin transporter density is indicative of elevated extracellular serotonin levels ( Mercado and Kilic, 2010 ; Jørgensen et al., 2014 ). However, decreased levels of serotonin are thought to play a role in depression, mania, and anxiety disorders ( Mohammad-Zadeh et al., 2008 ), including obsessive-compulsive disorder (for a discussion of the relationship between serotonin and OCD, see Baumgarten and Grozdanovic, 1998 ; Rantala et al., 2019 ). One study showed that a sample of mainly women (85% women) experiencing romantic love have similar levels of serotonin transporter density to a sample of both women and men (50% women) with obsessive-compulsive disorder ( Marazziti et al., 1999 ), which could account for the intrusive thinking or preoccupation with the loved one associated with romantic love ( Hatfield and Sprecher, 1986 ).

Lower dopamine transporter density and lower dopamine transporter maximal velocity in lymphocytes have been found in people experiencing romantic love ( Marazziti et al., 2017 ). This is indicative of increased dopamine levels ( Marazziti et al., 2017 ) and is consistent with neuroimaging studies (e.g., Takahashi et al., 2015 ; Acevedo et al., 2020 ) showing activation of dopamine-rich regions of the mesolimbic pathway. One study ( Dundon and Rellini, 2012 ) found no difference in dopamine levels in urine in women experiencing romantic love compared with a control group. Dopamine is involved in reward behavior, sleep, mood, attention, learning, pain processing, movement, emotion, and cognition ( Ayano, 2016 ). Up-regulation of the dopamine system could help to explain the motivational characteristics of romantic love such as longing for reciprocity, desire for complete union, service to the other, and maintaining physical closeness ( Hatfield and Sprecher, 1986 ).

There are no studies that have specifically investigated oxytocin levels in romantic love (at least none that measure romantic love with a validated scale). However, studies ( Schneiderman et al., 2012 , Schneiderman et al., 2014 ; Ulmer-Yaniv et al., 2016 ) have demonstrated that people in the early stages of their romantic relationship have higher levels of plasma oxytocin than controls (singles and new parents). We infer this to mean that reciprocated romantic love is associated with elevated oxytocin levels. Oxytocin plays a role in social affiliation ( IsHak et al., 2011 ) and pair-bonding ( Young et al., 2011 ; Acevedo et al., 2020 ). Oxytocin receptors are prevalent throughout the brain including in the mesolimbic pathway (e.g., Bartels and Zeki, 2000 ). Elevated oxytocin could account for many of the behavioral features of romantic love such as actions toward determining the other’s feelings, studying the other person, service to the other, and maintaining physical closeness ( Hatfield and Sprecher, 1986 ).

Romantic love has been associated with elevated cortisol levels ( Marazziti and Canale, 2004 ), although this has not been replicated ( Sorokowski et al., 2019 ), and one study measuring cortisol in saliva found the opposite ( Weisman et al., 2015 ). Different results could be attributed to different length of time in a relationship between the samples (see Garcia, 1997 ; de Boer et al., 2012 ). Cortisol plays a role in the human stress response by directing glucose and other resources to various areas of the body involved in responding to environmental stressors while simultaneously deactivating other processes (such as digestion and immune regulation, Mercado and Hibel, 2017 ). Elevated cortisol levels may play a role in pair-bond initiation ( Mercado and Hibel, 2017 ) and are indicative of a stressful environment.

Romantic love is associated with higher levels of nerve growth factor, and the intensity of romantic love correlates with levels of nerve growth factor ( Emanuele et al., 2006 ). Nerve growth factor is a neurotrophic implicated in psycho-neuroendocrine plasticity and neurogenesis ( Berry et al., 2012 ; Aloe et al., 2015 ; Shohayeb et al., 2018 ) and could contribute to some of the neural and endocrine changes associated with romantic love.

Insights From the Mechanisms of Psychopathology

Despite “madness” being mentioned in one review of the neurobiology of love ( Zeki, 2007 ) and psychopathology being discussed in studies investigating the endocrinology of romantic love (e.g., Marazziti et al., 1999 , 2017 ), the similarities between romantic love and psychopathology are under-investigated. An understanding of the mechanisms that regulate addiction, mood disorders, and anxiety disorders may help to shed light on the psychological characteristics and mechanisms underlying romantic love and identify areas for future research.

Conceptualizing romantic love as a “natural addiction” (e.g., Fisher et al., 2016 ) not only helps to explain romantic love’s psychological characteristics but provides insight into the mechanisms underlying it (e.g., Zou et al., 2016 ). For example, a neurocircuitry analysis of addiction, drawing on human and animal studies, reveals mechanisms of different “stages” of addiction that have implications for romantic love: binge/intoxication (encompassing drug reward and incentive salience), withdrawal/negative affect, and preoccupation/anticipation ( Koob and Volkow, 2016 ). Each of these stages is associated with particular neurobiological activity and each stage could be represented in romantic love. This may mean that the findings of studies investigating the neurobiology of romantic love (which rely primarily on studies where visual stimuli of a loved one are presented) equates to the binge/intoxication stage of addiction. Findings from studies investigating romantic rejection ( Fisher et al., 2010 ; Stoessel et al., 2011 ; Song et al., 2015 ) may equate to the withdrawal/negative affect stage of addiction. Findings from resting-state fMRI studies ( Song et al., 2015 ; Wang et al., 2020 ) may equate to the preoccupation/anticipation stage of addiction. The result is that current neuroimaging studies may paint a more detailed picture of the neurobiology of romantic love than might initially be assumed.

Mood is an emotional predictor of the short-term prospects of pleasure and pain ( Morris, 2003 ). The adaptive function of mood is, essentially, to integrate information about the environment and state of the individual to fine-tune decisions about behavioral effort ( Nettle and Bateson, 2012 ). Elevated mood can serve to promote goal-oriented behavior and depressed mood can serve to extinguish such behavior ( Wrosch and Miller, 2009 ; Bindl et al., 2012 ; Nesse, 2019 ). Anxious mood is a response to repeated threats ( Nettle and Bateson, 2012 ). Because romantic love can be a tumultuous time characterized by emotional highs, lows, fear, and trepidation, and can involve sustained and repetitive efforts to pursue and retain a mate, it follows that mood circuitry would be closely intertwined with romantic love. Additionally, because romantic love concerns itself with reproduction, which is the highest goal in the realm of evolutionary fitness, it makes sense that mood may impact upon the way romantic love manifests. Understanding the mechanisms that regulate mood can provide insights into psychological characteristics of romantic love and the mechanisms that regulate it. No studies have directly investigated the mechanisms that contribute to changes in mood in people experiencing romantic love. However, insights can be taken from research into the mechanisms of mood and anxiety disorders.

While addiction, hypomania, depression, and anxiety symptoms in people experiencing romantic love may be the normal manifestation of particular mechanisms, symptoms associated with psychopathology may be the manifestations of malfunctioning mechanisms as a result of evolutionary mismatch (see Durisko et al., 2016 ; Li et al., 2018 ). As a result, the mechanisms that cause romantic love and those that cause psychopathology may not be precise models with which to investigate the other. Nonetheless, the mechanisms that cause psychopathology may provide a useful framework with which to base future research into romantic love. Conversely, it may also be that our understanding of the mechanisms that cause romantic love could be a useful framework with which to further investigate psychopathology.

The drug reward and incentive salience features of the binge/intoxication stage of addiction involve changes in dopamine and opioid peptides in the basal ganglia (i.e., striatum, globus pallidus, subthalamic nucleus, and substantia nigra pars reticulata, Koob and Volkow, 2016 ). No research has investigated opioids in romantic love, despite them being involved in monogamy in primates (see French et al., 2018 ) and pair-bonding in rodents ( Loth and Donaldson, 2021 ). The negative emotional states and dysphoric and stress-like responses in the withdrawal/negative affect stage are caused by decreases in the function of dopamine in the mesolimbic pathway and recruitment of brain stress neurotransmitters (i.e., corticotropin-releasing factor, dynorphin), in the extended amygdala ( Koob and Volkow, 2016 ). No studies have investigated corticotropin-releasing factor in romantic love. The craving and deficits in executive function in the preoccupation/anticipation stage of addiction involve the dysregulation of projections from the prefrontal cortex and insula (e.g., glutamate), to the basal ganglia and extended amygdala ( Koob and Volkow, 2016 ). No studies have investigated glutamate in romantic love. There are at least 18 neurochemically defined mini circuits associated with addiction ( Koob and Volkow, 2016 ) that could be the target of research into romantic love. It is likely that romantic love has similar, although not identical, mechanisms to addiction (see Zou et al., 2016 ; Wang et al., 2020 ).

Mania/hypomania (bipolar disorder)

Similar to the brain regions implicated in romantic love, the ventral tegmental area has been associated with mania ( Abler et al., 2008 ), the ventral striatum has been associated with bipolar disorder ( Dutra et al., 2015 ), and the amygdala has been associated with the development of bipolar disorder ( Garrett and Chang, 2008 ). These findings should be interpreted with caution, however, as replicating neuroimaging findings in bipolar disorder has proven difficult (see Maletic and Raison, 2014 ). Research implicates two interrelated prefrontal–limbic networks in elevated mood, which overlap with activity found in romantic love: the automatic/internal emotional regulatory network which includes the ventromedial prefrontal cortex, subgenual anterior cingulate cortex, nucleus accumbens, globus pallidus, and the thalamus, and the volitional/external regulatory network which includes the ventrolateral prefrontal cortex, mid- and dorsal-cingulate cortex, ventromedial striatum, globus pallidus, and thalamus ( Maletic and Raison, 2014 ).

Norepinephrine (theorized to be involved in romantic love, e.g., Fisher, 1998 , 2000 ), serotonin, dopamine, and acetylcholine play a role in bipolar disorder ( Manji et al., 2003 ). One study ( Dundon and Rellini, 2012 ) found no difference in norepinephrine levels in urine in women experiencing romantic love compared with a control group. No studies have investigated acetylcholine in romantic love but romantic love is associated with serotonin ( Marazziti et al., 1999 ; Langeslag et al., 2012 ) and dopamine activity ( Marazziti et al., 2017 ). Similar to the endocrine factors implicated in romantic love ( Emanuele et al., 2006 ; Schneiderman et al., 2012 , 2014 ; Ulmer-Yaniv et al., 2016 ), bipolar patients in a period of mania have also demonstrated higher oxytocin ( Turan et al., 2013 ) and nerve growth factor ( Liu et al., 2014 ) levels and lower levels of serotonin ( Shiah and Yatham, 2000 ). Additionally, there is some evidence that women diagnosed with bipolar disorder present with higher levels of testosterone whereas men present with lower levels of testosterone compared with sex-matched controls ( Wooderson et al., 2015 ). Similar findings have been found in romantic love ( Marazziti and Canale, 2004 ). Dysfunction in the hypothalamic–pituitary–adrenal axis, where cortisol plays a major role, has also been implicated in bipolar disorder ( Maletic and Raison, 2014 ). Cortisol probably plays a role in romantic love ( Marazziti and Canale, 2004 ; Weisman et al., 2015 ).

Neuroimaging studies have implicated changes in functional connectivity in the neural circuits involved in affect regulation in people experiencing depression ( Dean and Keshavan, 2017 ). Increased functional connectivity has been found in networks involving some of the same regions, such as the amygdala, the medial prefrontal cortex, and nucleus accumbens in both people experiencing romantic love and people who recently ended their relationship while in love ( Song et al., 2015 ).

There are a number of endocrine similarities between romantic love and depression. One major pathophysiological theory of depression is that it is caused by an alteration in levels of one or more monoamines, including serotonin, norepinephrine, and dopamine ( Dean and Keshavan, 2017 ). Altered dopamine transmission in depression may be characterized by a down-regulated dopamine system (see Belujon and Grace, 2017 ), which is inferred from numerous human and animal studies, including successful treatment in humans with a dopamine agonist. In romantic love, however, dopamine appears to be up-regulated, especially in areas of the mesolimbic pathway (e.g., Marazziti et al., 2017 ; Bartels and Zeki, 2000 ; Acevedo et al., 2020 ). This could account for some findings that romantic love is associated with a reduction in depression symptoms ( Bajoghli et al., 2013 , 2017 ). However, these need to be reconciled with contrasting findings that romantic love is associated with increased depression symptoms ( Bajoghli et al., 2014 ; Kuula et al., 2020 ) and evidence suggesting that a relationship breakup in people experiencing romantic love is associated with depression symptoms ( Stoessel et al., 2011 ; Price et al., 2016 ; Verhallen et al., 2019 ). The mechanisms that underlie depression might provide a framework for such efforts.

Dysregulation of the HPA axis and associated elevated levels of cortisol is theorized to be one contributor to depression ( Dean and Keshavan, 2017 ). Changes in oxytocin and vasopressin systems (theorized to be involved in romantic love, e.g., Fisher, 1998 , 2000 ; Carter, 2017 ; Walum and Young, 2018 ) are associated with depression (see Purba et al., 1996 ; Van Londen et al., 1998 ; Neumann and Landgraf, 2012 ; McQuaid et al., 2014 ). No studies have investigated vasopressin in people experiencing romantic love. There is also decreased neurogenesis and neuroplasticity in people experiencing depression ( Dean and Keshavan, 2017 ), the opposite of which can be inferred to occur in romantic love because of its substantial neurobiological activity and elevated nerve growth factor (see Berry et al., 2012 ; Aloe et al., 2015 ; Shohayeb et al., 2018 ).

The insular cortex, cingulate cortex, and amygdala are implicated in anxiety and anxiety disorders ( Martin et al., 2009 ). There is also evidence that cortisol, serotonin and norepinephrine are involved ( Martin et al., 2009 ). The substantial overlap between the mechanisms regulating romantic love and those causing anxiety and anxiety disorders provides an opportunity to investigate specific mechanistic effects on the psychological characteristics of romantic love. Assessing state anxiety and these mechanisms concurrently in people experiencing romantic love may be a fruitful area of research.

There is also a need to clarify the role of the serotonin system in romantic love. Similar serotonin transporter density in platelets in people experiencing romantic love and OCD suggests a similar serotonin-related mechanism in both ( Marazziti et al., 1999 ). However, lower serotonin transporter density in platelets is indicative of higher extracellular serotonin levels ( Mercado and Kilic, 2010 ; Jørgensen et al., 2014 ). This is despite lower levels of serotonin being theorized to contribute to anxiety ( Mohammad-Zadeh et al., 2008 ). One study found lower circulating serotonin levels in men experiencing romantic love than controls and higher levels of circulating levels of serotonin in women experiencing romantic love than controls ( Langeslag et al., 2012 ). Insights from the mechanisms regulating anxiety disorders may help to provide a framework with which to further investigate the role of the serotonin system in romantic love and reconcile these findings.

Insights From Cognitive Biases

Positive illusions are cognitive biases about a relationship and loved one that are thought to have positive relationship effects ( Song et al., 2019 ). The research into positive illusions does not use samples of people explicitly experiencing romantic love, and instead uses people in varied stages of a romantic relationship, including those in longer-term pair-bonds. One study ( Swami et al., 2009 ), however, did find a correlation between the “love-is-blind bias” (one type of positive illusion) and eros scores. We also know that cognitive biases resembling positive illusions do exist in romantic love. Both the Passionate Love Scale (e.g., “For me, ____ is the perfect romantic partner,” Hatfield and Sprecher, 1986 , p. 391) and the eros subscale of the Love Attitudes Scale (e.g., “My lover fits my ideal standards of physical beauty/handsomeness,” Hendrick and Hendrick, 1986 , p. 395) include questions about a respondent’s loved one that resemble measures of positive illusions. Understanding the mechanism that regulates positive illusions will provide a model against which the mechanisms regulating the cognitive features of romantic love can be assessed.

A proposed mechanism of positive illusions includes the caudate nucleus, dorsal anterior cingulate cortex, ventral anterior cingulate cortex, orbitofrontal cortex, ventrolateral prefrontal cortical regions, and dorsal medial prefrontal cortex ( Song et al., 2019 ). These regions overlap with the brain regions associated with romantic love. This suggests that the cognitive biases associated with romantic love may be related to, but are distinct from, positive illusions. Targeted neuroimaging studies could ascertain any involvement of the ventrolateral prefrontal cortex and the dorsal medial prefrontal cortex in romantic love. Such research could help to delineate a mechanism that specifically regulates one cognitive aspect of romantic love from those that regulate other psychological aspects of romantic love.

Insights From Mammalian Pair-Bonding Mechanisms

It is not possible to say with any certainty if other animals experience romantic love. Some certainly engage in pair-bonding and exhibit behaviors that are characteristic of romantic love such as obsessive following, affiliative gestures, and mate guarding (see Fisher et al., 2006 ). While some similarities between humans and other animals may be the result of parallel evolution, an understanding of the mechanisms involved in pair-bond formation in other animals can raise questions and guide research into romantic love in humans. Research into monogamous prairie voles, in particular, has identified neurobiological and endocrinological mechanisms that regulate pair-bonding processes. Drawing on this research, a hypothetical neural circuit model of pair-bond formation (pair-bonding) that includes the ventral tegmental area, nucleus accumbens, paraventricular nucleus, amygdala, hippocampus, anterior olfactory nucleus, and medial prefrontal cortex has been proposed ( Walum and Young, 2018 ). Research implicates oxytocin, vasopressin, dopamine, and, potentially, serotonin and cortisol in pair-bonding ( Walum and Young, 2018 ). Most of these neural regions and endocrine factors have been implicated in romantic love in humans. The implications of this research become apparent when the phylogeny of romantic love is presented.

When applied to romantic love, the second of Tinbergen’s (1963) four questions asks: “How does romantic love develop over the lifetime of an individual?” This can be answered with reference to the age of onset of romantic love, its presence throughout the lifespan, and its duration. Questions of ontogeny also encompass issues around the internal and external influences on romantic love ( Tinbergen, 1963 ; Zeifman, 2001 ). We have also chosen to include some consideration of culture in this section because it influences the causes of romantic love. We find that romantic love first develops in childhood, is experienced at all ages in both sexes, usually lasts months or years, but can exist for many years or decades. It is influenced by a range of internal and external factors and is similar across cultures. The modern environment may influence romantic love in ways not present in our evolutionary history.

Romantic Love Over the Lifetime

Romantic love occurs from childhood through adulthood. It first manifests before puberty ( Hatfield et al., 1988 ), with boys and girls as young as four reporting experiences that equate to romantic love. Adolescence is the time in which romantic love first manifests with all of its characteristic features ( Hatfield and Sprecher, 1986 ), including the onset of sexual desire and activity and, potentially, pair-bonding. Romantic love may be more common among adolescents than young adults. In one study ( Hill et al., 1997 ), American university psychology students reported a greater occurrence of mutual and unrequited love experiences when they were 16–20 years old compared to when they were 21–25 years old. However, romantic love exists at all ages of adulthood in both sexes ( Wang and Nguyen, 1995 ).

There are few studies of psychological sex differences in romantic love. Those that exist (e.g., Hatfield and Sprecher, 1986 ; Hendrick and Hendrick, 1995 ; Cannas Aghedu et al., 2018 ) compare the overall intensity of romantic love and find no difference or slightly more intense romantic love in women than men. To our knowledge, no research has specifically investigated sex differences in duration or form of romantic love although it has been shown that some precursors to romantic love may play a greater role in one sex than the other (see Pines, 2001 ; Sprecher et al., 1994 ; Riela et al., 2010 ). As highlighted above, there are small sex differences in the neurobiology of romantic love ( Bartels and Zeki, 2004 ; Fisher et al., 2006 ) and sex differences may exist in the activity of testosterone ( Marazziti and Canale, 2004 ) and serotonin ( Langeslag et al., 2012 ) in people experiencing romantic love, although findings have been inconsistent. These neurobiological and endocrinological differences may, presumably, have differential effects on the presentation of romantic love which have not yet been identified by research.

The psychological features of romantic love are said to normally last between 18 months to 3 years ( Tennov, 1979 ), although studies have found that serotonin transporter density, cortisol levels, testosterone levels, follicle-stimulating hormone levels, and nerve growth factor levels do not differ from controls 12–24 months after initial measurement ( Marazziti et al., 1999 ; Marazziti and Canale, 2004 ; Emanuele et al., 2006 ). Unrequited love has been shown to last an average duration of between 10 and 17 months, depending on the type of unrequited love ( Bringle et al., 2013 ). In that study, unrequited love for someone that an individual pursued lasted the shortest period of time (10.12 months) and romantic love for someone who an individual knows but has not revealed their love to lasted the longest (18.44 months) in a sample of high school and university students from the United States. This contrasts with reciprocated romantic love that lasted even longer (an average of 21.33 months).

The early stages of romantic love characterized by stress may be distinct from a later period characterized by feelings of safety and calm ( Garcia, 1997 ; de Boer et al., 2012 ). The first stage, which is characterized by approximately the first 6 months of a relationship, has been described as “being in love.” It is marked by all the characteristics of romantic love, including, especially, romantic passion and intimacy. The second phase, which has been said to last from approximately 6 months to 4 years, has been referred to as “passional love.” During this time passion is maintained but commitment and intimacy increase. Passional love gives way to companionate love, passion subsides, and commitment and intimacy reach their peaks. While a description of these phases is informative, it is important to recognize that only one study has investigated these phases and they used a sample of predominately university students ( Garcia, 1997 ). Mechanisms research has not adopted these stages and “early stage” romantic love does not specifically refer to the first 6 months of a romantic relationship.

Romantic love exists on a continuum of intensity but can be classified categorically ( Hatfield and Sprecher, 1986 ). The authors of the Passionate Love Scale ( Hatfield and Sprecher, 2011 ) have developed arbitrary cutoffs for differing intensities of romantic love. However the thresholds that define them are not theoretically or empirically derived and are yet to be widely accepted in the literature.

Romantic love can commence abruptly or build up slowly, although the phenomenon of “love at first sight” may actually be strong attraction rather than romantic love, per se ( Sternberg, 1986 ; Zsok et al., 2017 ). In one study of Chinese and American participants, 38% of participants fell in love fast and 35% fell in love slow, with the remaining unknown ( Riela et al., 2010 ). Another study, of Iranians, found that 70% of participants fell in love slowly or very slowly ( Riela et al., 2017 ). Romantic love can end abruptly but often wanes slowly.

Regardless of the normal duration of romantic love, there is a general inverse relationship between the length of time in a relationship and romantic love ( Hatfield et al., 2008 ; Acevedo and Aron, 2009 ). Romantic love normally gives way to failure of a relationship to form, a relationship breakup, or transition to companionate love. However, in some individuals, romantic love can last many years, or even, decades ( O’Leary et al., 2011 ; Acevedo et al., 2012 ; Sheets, 2013 ). In romantic relationships that last, romantic love serves to bond partners together by creating shared understandings, emotions, and habits ( Hatfield and Walster, 1985 ) characteristic of companionate love and long-term pair-bonds. The transition from romantic love to companionate love is gradual and both types of love share many characteristics. In circumstances where romantic love is maintained beyond the initial few years, obsessive thinking about a partner is no longer a feature (e.g., Acevedo and Aron, 2009 ; O’Leary et al., 2011 ).

Internal and External Influences

A number of internal and external influences affect when, with whom, and how we fall in love. The scenario of attachment, separation, and loss in young children ( Bowlby, 1969 , 1973 , 1980 ) is similar to a “desire for union” and may be the groundwork for romantic attachments in later life ( Hatfield et al., 1988 ). To this extent, romantic love, like newborn/infant attachment, is “prewired” into humans as part of their evolutionary heritage ( Hatfield et al., 1989 ). Researchers “focus their investigations on the effects of mother-infant bonding in order to explain variations in the form, duration, and/or frequency of adult passionate relationships” ( Fisher, 1998 , p. 31). For example, a person’s adult attachment style is determined in part by childhood relationships with parents ( Hazan and Shaver, 1987 ) and this may have implications for the experience of romantic love (e.g., Hendrick and Hendrick, 1989 ; Aron et al., 1998 ). Romantic love is positively associated with a secure attachment style and negatively associated with an avoidant attachment style.

Precursors to romantic love include reciprocal liking, appearance, personality, similarity, social influence, filling needs, arousal, readiness, specific cues, isolation, mysteriousness, and propinquity (see Aron et al., 1989 ; Sprecher et al., 1994 ; Riela et al., 2010 ; Riela et al., 2017 ; see also Hazan and Diamond, 2000 ; Fisher, 2011 ). Research also suggests that conscious variables (personality and appearance), situational variables (proximity and arousal), lover variables (lover finds us attractive, lover fills important needs, similarity, and lover is best friend), and unconscious variables (similarity to relationship with parents, similarity of lover to father, similarity of lover to mother, and love at first sight) contribute to with whom we fall in love ( Pines, 2005 ). The majority of precursors are an interplay between internal and external influences.

Some of the most important precursors to romantic love include personality, reciprocal liking, physical appearance, propinquity, specific cues, readiness, and similarity ( Aron et al., 1989 ; Sprecher et al., 1994 ; Riela et al., 2010 , 2017 ). Personality is the “attractiveness of the other’s personality (e.g., intelligent, humorous)” ( Riela et al., 2010 , p. 474). This represents an interplay between internal influences (the preferences of the individual or what they find attractive) and external influences (the personality characteristics of the potential loved one). Reciprocal liking has been defined above and is a mixture of internal and external influences. Physical appearance, too, is an interplay between what an individual finds attractive, either through genetic predisposition or learned experience, and the physical attributes of the potential loved one. Propinquity has been defined and discussed above and is a combination of internal and external influences. Similarity is “having things in common, including attitudes, experiences, interests, and personal factors such as appearance, personality, and family background ( Riela et al., 2010 , p. 474). This is contingent upon both the individual’s characteristics (internal influence) and the potential loved one’s characteristics (external influence).

There are, however, some precursors that are explicitly internal or external influences. Readiness is “being emotionally or physically prepared for seeking a romantic relationship, such as having just broken up with someone and seeking comfort in a new partner” ( Riela et al., 2010 , p. 475). This can be a largely internal influence that can cause romantic love. Specific cues are “particular characteristics of the other (e.g., smile, shape of the eyes), that are relevant to the perceiver in producing strong attractions. This is not the same as attractiveness in general but refers to highly idiosyncratic features of potential love objects that are specifically important to the individual” ( Riela et al., 2010 , p. 475). These are largely external influences that cause romantic love, although they do trigger a biological or psychological response which is internally determined.

Cross-Cultural Perspectives

There have been a number of books (e.g., Jankowiak, 1995 , 2008 ) and studies that shed light on the cross-cultural nature of romantic love. The sum of research indicates that romantic love is probably universal (although the research is yet to prove this unequivocally) with relatively few psychological differences found between cultures (although cultures respond to love in different ways). An ethnographic analysis of 166 cultures from the Standard Cross-Cultural Sample ( Jankowiak and Fischer, 1992 ; Jankowiak and Paladino, 2008 ) found no evidence of romantic love in only 15 cultures, and this was largely due to lack of data. Validated measures of romantic love (i.e., Passionate Love Scale, Love Attitudes Scale, Triangular Love Scale) have been used in at least 50 countries ( Feybesse and Hatfield, 2019 ). The Triangular Theory of Love is robust cross-culturally ( Sorokowski et al., 2020 ). Cross-cultural accounts of the features and the intensity of romantic love are remarkably similar (see Feybesse and Hatfield, 2019 for a review of cross-cultural perspectives on romantic love). Multiple neuroimaging studies have ascertained that the same neural mechanisms associated with romantic love in American samples are associated with romantic love in Chinese samples ( Xu et al., 2011 , 2012b ).

Romantic love may be thought of more positively among Western countries than other countries and Westerners report falling in love more often (see Feybesse and Hatfield, 2019 ). Cultural differences have also been identified in the role of precursors in causing romantic love. A comparison between Japanese, Russian, and American populations found that culture played a role in the self-reported importance of personality, physical appearance, propinquity, similarity, readiness, isolation, mystery, and social standing ( Sprecher et al., 1994 ). Some differences have also been found between Chinese and Americans ( Riela et al., 2010 ) and between Iranians and Americans ( Riela et al., 2017 ) using similar and different methods. In some cultures, romantic love is suppressed and arranged marriages predominate (discussed below).

Evolutionary Mismatch

The evolutionary mismatch hypothesis argues that humans are now living in environments vastly different from those in which they evolved and, as a result, biological mechanisms may not interact with the environment in the manner that they originally evolved to Li et al. (2018) . Adaptations may malfunction. This has implications for the functioning of mechanisms and psychology. Evolutionary mismatch may influence the occurrence, duration, form, and experience of romantic love. As already suggested, evolutionary mismatch may influence the degree to which certain social mechanisms play a role in causing romantic love. This may have flow-on impacts on the frequency with which an individual falls in love or with whom they fall in love. The increased exposure to potential mates may also lead to greater instances of relationship dissolution and new instances of romantic love than would have been the case in our evolutionary history. Evolutionary mismatch may also influence the duration of romantic love. Under evolutionary conditions, romantic love would usually occur in the context of reproduction, pregnancy, and childbirth (see Goetz et al., 2019 ). This may mean that the duration of romantic love may have been shorter in females than is the case in modern developed societies because they are overcome by mother-infant bonding, possibly at the expense of romantic love.

The form and experience of romantic love may also be impacted by evolutionary mismatch. Technology means that lovers are able to maintain regular contact (e.g., by telephone) or be exposed to images of the loved one (e.g., by photographs) in the absence of physical contact. This consistent exposure may be associated with more frequent activation of neural structures associated with romantic love (i.e., reward and motivation structures) and change the intensity or subjective experience of romantic love compared to evolutionary ancestors who may have been completely separated for periods of time.

Ultimate Perspectives

When applied to romantic love, the third of Tinbergen’s (1963) four questions asks: “What are the fitness-relevant functions of romantic love?” Functional explanations address the fitness ramifications (survival and reproduction) of the behavior or trait of interest ( Tinbergen, 1963 ; Zeifman, 2001 ; Bateson and Laland, 2013 ). We are, thus, concerned with both the fitness-relevant benefits and costs of romantic love. We have outlined the benefits and costs of romantic love associated with five functions based on a small literature on the subject (i.e., Fletcher et al., 2015 ; Buss, 2019 ), reproduction-related literature, and our consideration of the subject. Some of the benefits we describe can be considered functions in their own right (e.g., Buss, 2019 ). Table 3 presents a summary of benefits and costs of romantic love according to five distinct yet interrelated functions: mate choice, courtship, sex, pair-bonding, and health. Our approach is to describe each function, present the benefits associated with each function, and present the costs associated with each function. Where relevant, we have included information about related concepts or theories. We contend that while there is a small amount of evidence for the health promoting benefits of romantic love, the evidence is insufficient to say with certainty that health promotion is a function of romantic love. We conclude this section by summarizing some potential selective pressures and describing romantic love as a complex suite of adaptations and by-products.

Reproduction- and survival-related benefits and costs associated with each function of romantic love.

Mate Choice

Romantic love serves a mate choice function ( Fisher et al., 2006 ). Both men and women engage in mate choice ( Stewart-Williams and Thomas, 2013 ). Assessing potential mates has important fitness consequences for individuals, as the benefits of finding a suitable mate are often higher than mating haphazardly or with a randomly selected mate ( Geary et al., 2004 ; Andersson and Simmons, 2006 ; Jones and Ratterman, 2009 ; Shizuka and Hudson, 2020 ). On the other hand, mate choice is a costly and error-prone activity and, thus, it may be adaptive to focus one’s attention on a particular mate that has been identified as a preferred partner ( Bowers et al., 2012 ). Romantic love serves this function.

Mate choice evolved in mammals to enable individuals to conserve their mating energy, choose between potential mates, and focus their attention on particular potential mating partners ( Fisher, 2000 ; Fisher et al., 2006 ). The focus of one’s attention on a single potential mate is not without costs (e.g., Klug, 2018 ; Bear and Rand, 2019 ). Imperfect mate choice (e.g., Johnstone and Earn, 1999 ) could result from imperfect information (e.g., Luttbeg, 2002 ) or acceptance or rejection errors. Imperfect information might include the concealment of information that has detrimental effects on fitness. Time to assess an individual is important in mate choice and imperfect mate choice could potentially be a greater problem in circumstances where romantic love is quick to arise. Mate choice, by definition, excludes other potential mates and romantic love, in fact, suppresses the search for other mates ( Fletcher et al., 2015 ). This cost can be exacerbated in certain environments such as those within which finding additional mates is relatively easy ( Kushnick, 2016 ). Romantic love can detract from other fitness-promoting goals such as career-advancing activities, physical health promoting activities, or forming and maintaining other social relationships.

Romantic love serves a courtship function ( Fisher et al., 2006 , 2016 ). Courtship involves a series of signals and behaviors that serve as a means of assessing potential partner quality and willingness to invest in a relationship ( Trivers, 1972 ; Wachtmeister and Enquist, 2000 ). One function of the attraction system is to pursue potential mates ( Fisher, 2000 ). People in love often engage in courtship of their loved one with the aim of persuading them that they are a good long-term mate.

The primary benefit of courtship in romantic love is that it can secure a mate that is prepared to commit to a relationship. To do this, both sexes can pursue potential mates, display commitment, and signal fidelity ( Buss, 2019 ). These acts are why love has been described as a commitment device ( Frank, 1988 ; Fletcher et al., 2015 ; Buss, 2019 ). Courtship allows individuals to learn about and assess the suitability of potential mates while displaying reproductively relevant resources ( Buss, 2019 ). Men emphasize characteristics such as resources, while women emphasize characteristics such as beauty, in an attempt to increase attractiveness ( Buss, 1988 ; Luoto, 2019a ). Men, at least historically, also provide signals of parental investment ( Buss, 2019 ). Literature on human courtship from an evolutionary perspective supports the notion of greater choosiness among females, predicted by parental investment theory ( Trivers, 1972 ), for short-term mating and less serious commitments. This effect, however, substantially diminishes for long-term mating endeavors and marriage commitment ( Kenrick et al., 1990 ). The literature also suggests that women are looking for specific cues, indicative of evolved preferences, during the courtship process ( Oesch and Miklousic, 2012 ).

There are costs associated with romantic love’s courtship function. These include the expenditure of a significant amount of time and resources and, if courtship efforts are not reciprocated, embarrassment ( Silver et al., 1987 ). Sometimes, individuals in love might engage in intrusive “obsessive pursuit” of someone who is not interested ( Spitzberg and Cupach, 2003 ). Courtship can be a particularly stressful time for an individual. There are also potential costs because individuals who are courting might find themselves in direct intrasexual competition with another individual who has an interest in their potential mate. Intrasexual competition can be costly because an individual must divert additional resources to this endeavor. An individual bears even greater costs if they lose this competition. Both sexes can be subject to costly signaling as part of courtship ( Griskevicius et al., 2007 ), although men are at risk of higher fitness costs associated with temporally extended courtships, despite this being interpreted as a sign of a good mate by women ( Seymour and Sozou, 2009 ).

Romantic love promotes sex and may increase the chances of pregnancy. Sex is an important part of romantic relationships and initiation into sex with a partner, and a greater frequency of sex, is associated with the earlier stages of a romantic relationship ( Call et al., 1995 ). Sex and pregnancy are not, however, features of romantic love in pre-pubescent children and pregnancy is not a feature of romantic love in post-menopausal women. The nature of reproduction is different in societies where contraception and family planning practices are widespread (see Goetz et al., 2019 , for review of evolutionary mismatch in human mating). In such circumstances, immediate pregnancy may not be a feature of romantic love, whereas sex often is. In such circumstances, romantic love may indirectly promote pregnancy by creating pair-bonds whose members later reproduce.

Romantic love provides sexual access ( Buss, 2019 ). Love is one of the most common reasons people give for having sex ( Ozer et al., 2003 ; Meston and Buss, 2007 ; Dawson et al., 2008 ; Meston and Buss, 2009 ). Given the relative willingness of men to engage in short-term mating compared to women, it follows that sex because of love plays a greater role in providing sexual access by women to men than the other way around ( Meston and Buss, 2007 ). Sex can facilitate a gain in reputation ( Meston and Buss, 2007 ) and both sexes increase their status by having children ( Buss et al., 2020 ). Sex is intrinsically pleasurable and reinforcing, and promotes bonding ( Meltzer et al., 2017 ). In times before the advent of contraception, repeated sex with a partner would usually result in pregnancy and childbirth ( Goetz et al., 2019 ; Kushnick, 2019 ). This is still the case in many parts of the world.

For example, there is evidence that features characteristic of romantic love may be associated with a greater number of children among the Hadza, a hunter gatherer tribe in northern Tanzania ( Sorokowski et al., 2017 ). Higher passion, which is definitive of romantic love (e.g., Sternberg, 1986 ), is associated with a greater number of children in women. The findings are important because the lifestyle of the Hadza more closely resembles the environment in which humans evolved than do industrialized or agrarian societies. As a result, inferences can be made about the adaptive function of passion in human evolutionary history. However, intimacy, another component of romantic love ( Sternberg, 1997 ), was found to be negatively correlated with number of children in women. Instead, commitment, a feature of companionate love, was associated with greater number of children in both women and men ( Sorokowski et al., 2017 ). Romantic love is normally relatively short-lived, and therefore the methods used in this study may not have been ideally suited to investigate the fitness consequences of romantic love. Nonetheless, this finding provides some support for the notion that romantic love promotes sexual access by women and facilitates reproduction.

One study ( Sorokowski et al., 2019 ) suggests that romantic love may increase the likelihood of a woman falling pregnant. Higher levels of the gonadotropins, follicle-stimulating hormone, and luteinizing hormone, and a non-significant but positive increase in estradiol to testosterone ratio in women experiencing romantic love could cause increased ovarian activity and increased estradiol synthesis, which might result in higher fecundity ( Sorokowski et al., 2019 ).

The costs associated with romantic love’s sex function are far greater for women than for men ( Trivers, 1972 ). Both sexes could be subject to unwanted pregnancy and associated parenting responsibilities (although this impacts women to a greater extent). There is also, however, a risk of damage to an individual’s reputation. Women are often subject to criticism from other women for engaging in sexual activity ( Koehn and Jonason, 2018 ), especially if a long-term relationship does not result. Men and women risk damage to their reputation for having sex with a low mate value partner, although men are generally treated far more favorably than women for engaging in sexual activity (see Zaikman and Marks, 2017 ). For women, a period of pregnancy followed by a lengthy period of lactation may ensue, and this is costly in terms of the ability to obtain sufficient resources and protecting oneself from harm. There is also the possibility that the relationship will dissolve following pregnancy and the woman may be left to raise a child without the father’s support ( Koehn and Jonason, 2018 ).

Pair-Bonding

Romantic love serves a pair-bonding function ( Fletcher et al., 2015 ). Pair bonding is both a process and a sate characterized by the formation of “enduring, selective attachments between sexual partners” ( Young et al., 2011 , p. 1). It differs from established pair-bonds and the neural characteristics of people experiencing romantic love differ somewhat from what is associated with longer-term pair-bonds (see Acevedo et al., 2012 , for distinction). Evolutionarily, when sex more often led to pregnancy, this pair-bonding would occur in the context of pregnancy and childbirth (although it is unclear if romantic love can exist at the same time as mother-infant bonding). This is still the case in many parts of the world. This is one possible reason for the duration of reciprocated romantic love to be between 18 months and 3 years ( Tennov, 1979 ) when not interrupted by childbirth. The intensity of specific neural activity in people experiencing romantic love is associated with relationship maintenance ( Xu et al., 2012a ).

Romantic love can establish long-term pair-bonds. In both sexes, romantic love promotes the provision of psychological and emotional resources ( Buss, 2019 ) as well as other types of caregiving ( Fletcher et al., 2015 ). It promotes relationship exclusivity through fidelity, jealousy, and mate-guarding ( Buss, 2019 ). Both sexes engage in additional mate retention tactics such as vigilance, mate concealment, monopolization of time, resource display, love and care, or sexual inducements ( Buss et al., 2008 ). Romantic love also promotes the sharing of other resources such as food or money. This benefit for women would have been, and often continues to be, greatest during times of lactation (see Marlowe, 2003 ; Quinlan, 2008 ). Both sexes can also benefit reputationally, as being in a relationship with a high mate value individual confers status, and individuals who are married or in a relationship are viewed more favorably than single people ( DePaulo and Morris, 2006 ). Men experiencing romantic love engage in actions that lead to successful reproductive outcomes ( Buss, 2019 ), such as protecting partners from physical harm. Men also engage in parenting ( Geary et al., 2004 ; Bribiescas et al., 2012 ), which could potentially result in increased offspring survival ( Fletcher et al., 2015 ).

When people are experiencing romantic love they are usually, but not always, interested in pursuing a “long-term mating strategy.” A long-term mating strategy is one that involves commitment, pair-bonding, and the parental investment (if children result) of both partners ( Buss, 2006 ). This contrasts with short-term mating strategies that do not often require public commitment, pair-bonding, and parental investment of the father ( Buss and Schmitt, 1993 ). Pair-bonding is characteristic of a long-term mating strategy.

The concept of romantic love serving as a commitment device is relevant to pair-bonding, as are the concepts of fitness interdependence ( Buss, 2019 ) and self-expansion. Fitness interdependence is the degree to which two people influence each other’s success in replicating their genes ( Aktipis et al., 2018 ). Romantic love binds two individuals together so that the potential reproductive success of one person is contingent upon the success of the other. The self-expansion model suggests that “people seek to expand their potential efficacy to increase their ability to accomplish goals” and that “one way people seek to expand the self is through close relationships, because in a close relationship the other’s resources, perspectives, and identities are experienced, to some extent, as one’s own” ( Aron and Tomlinson, 2019 , p. 2). Fitness interdependence and self-expansion can be increased in people experiencing romantic love.

There are substantial costs associated with pair-bonding ( Kushnick, 2016 ; Klug, 2018 ). Both sexes are potentially missing out on long-term mating opportunities with other suitable mates and are more restricted in terms of short-term mating opportunities ( Geary et al., 2004 ). There is a potential for damage to an individual’s reputation if they are in a relationship with a low mate value individual ( Buss, 2016 ). Both sexes share resources. Pair-bonding is associated with a reduction in the size of an individual’s support network ( Burton-Chellew and Dunbar, 2015 ). Jealousy can have negative effects upon a relationship ( Buss, 2000 , 2019 ; Hatfield et al., 2016 ) and there is a potential for emotional or physical harm arising from a relationship. People sometimes engage in homicide of their current or former partners in response to infidelity, or as a result of jealousy or a breakup ( Buss, 2000 , 2019 ; Shackelford et al., 2003 ). Some women engage in this behavior, but it is predominately a male behavior, when it occurs ( Buss, 2019 ). Stalking can occur following a breakup ( Spitzberg and Cupach, 2003 ; Buss, 2019 ) or, more generally, as a result of romantic love ( Marazziti et al., 2015 ). There is the potential for grief or depression symptoms following the breakup of a relationship ( Verhallen et al., 2019 ). Changing living arrangements, dividing up resources, and legal costs could all be necessary following the dissolution of a pair-bond ( Bear and Rand, 2019 ). Sex-specific costs include sexual obligations to a partner from women and parental investment by men ( Geary et al., 2004 ; Luoto, 2019a ).

While there is evidence that successful pair-bonding is associated with better health and survival ( Fletcher et al., 2015 ), there is little evidence showing that romantic love is associated with good health. Falling in love is associated with alteration in immune cell gene regulation in young women ( Murray et al., 2019 ). Specifically, falling in love is associated with genetic changes that could potentially result in an up-regulation of immune responses to viruses.

Experiencing romantic love for a recently gained partner is associated with the “active/elated” symptoms of hypomania ( Brand et al., 2007 , 2015 ). These symptoms are considered as favorable, “bright side” symptoms and contrast with unfavorable “dark side” symptoms such as disinhibition/stimulation-seeking and irritable/erratic dimensions ( Brand et al., 2015 ). Despite their association with hypomania, the favorable nature of these symptoms in romantic love may be a sign of good physical and mental health because higher hypomanic scores have been associated with higher “mental toughness,” increased physical activity, lower symptoms of depression, and lower sleep complaints ( Jahangard et al., 2017 ). Additionally, falling in love with a partner is sometimes associated with a reduction in depressive symptoms ( Bajoghli et al., 2013 , 2017 ). A reduction in the number of sexual partners could result in a decreased risk of sexually transmitted infections. There is evidence that romantic love might sometimes be associated with improved sleep quality ( Brand et al., 2007 ; Bajoghli et al., 2014 ).

There are some health-related costs associated with romantic love for both sexes. Despite a reduced risk of sexually transmitted infections being a benefit of romantic love, engaging in sexual activity at all may represent an increased risk of sexually transmitted infection, resulting in a cost to some ( Buss, 2016 ; Koehn and Jonason, 2018 ). Infertility from sexually transmitted infections is possible among women ( Koehn and Jonason, 2018 ). Disinhibited/stimulation-seeking and irritable/erratic, depressed, and anxious mood are sometimes features of romantic love ( Wang and Nguyen, 1995 ; Bajoghli et al., 2013 , 2014 , 2017 ; Brand et al., 2015 ; Kuula et al., 2020 ). In the face of repeated unrewarding efforts or adverse events in the courtship process, depressed or anxious mood could result ( Nettle and Bateson, 2012 ). Romantic rejection can result in a major depressive episode or even suicide (see Rantala et al., 2018 ). Despite evidence of improved sleep quality in people experiencing romantic love in some studies ( Brand et al., 2007 ; Bajoghli et al., 2014 ), one study ( Kuula et al., 2020 ) found poorer sleep quality, later sleep timing, and shorter sleep duration (one feature commonly found in studies relied upon to suggest a sleep quality benefit of romantic love) in adolescent girls experiencing romantic love. This suggests that altered sleep may in fact be a detrimental cost in some people experiencing romantic love. Women have the added risk of birth-related complications and death, which has been common in humans until recently in developed countries ( Goldenberg and McClure, 2011 ).

Selective Pressures

The literature contains three interesting theories of possible selective pressures for romantic love. They are framed in the context of promoting the evolution of pair-bonds, but as will be detailed below, the evolution of pair bonds and romantic love are likely to be inexorably linked. All three theories relate to the provision of resources by males to females. The first theory is that pair-bonds and romantic love may have emerged prior to 4 million years ago when bipedalism emerged and hominins moved into the woodlands and savannahs of our ancestral homelands (see Fisher et al., 2016 ). The need for mothers to carry infants in their arms may have driven them to select partners that were wired for pair-bonds which was associated with provisioning, defense, and other forms of support.

The second theory is that biparental care was a driving force in the emergence of long-term mating strategies ( Conroy-Beam et al., 2015 ). A game theoretical approach contends that females selecting males that were wired for pair-bonds directly increased the chances of offspring survival through the provisioning of tangible and intangible resources to the female and offspring. If biparental care was a driving force in the formation of pair-bonds in humans, it would be a uniquely human pressure, as biparental care has been generally identified as a consequence, rather than a cause, of pair-bonds in mammals ( Opie et al., 2013 ; Lukas and Clutton-Brock, 2013 ). This theory also has to contend with the fact that father presence is often not associated with better offspring survival in societies with little access to health care or contraception (see Fletcher et al., 2015 ).

The third theory is that a need for increased fecundity drove the selection of pair-bonds ( Conroy-Beam et al., 2015 ). Periods of malnutrition cause decreased fecundity. Once again, a game theoretical approach suggests that the selection of males that were wired for pair-bonds, which is associated with provisioning of females, increased the caloric intake of females over prolonged periods of time and, in turn, increased fecundity. This hypothesis is appealing because this selective pressure could have been present at any stage among the four hypotheses we propose for the emergence of pair-bonds in a section below.

Romantic Love Is a Complex Suite of Adaptations and By-Products

In evolutionary psychology, an adaptation is “…an inherited and reliably developing characteristic that came into existence as a feature of a species through natural selection because it helped to directly or indirectly facilitate reproduction during the period of its evolution” ( Buss et al., 1998 , p. 535; see also Williams, 2019 ). This approach is based, rightly, on the difficulty of testing hypotheses about the adaptive benefits of traits in ancestral environments. There is an equally valid approach, however, adopted by behavioral ecologists, that views current utility of adaptations as evidence that can be extrapolated to the past ( Fox and Westneat, 2010 ). One definition that has arisen from this approach is that “[a]n adaptation is a phenotypic variant that results in the highest fitness among a specified set of variants in a given environment” ( Reeve and Sherman, 1993 , p. 9).

Taken together, these two approaches to adaptation support the view that romantic love is a “complex suite of adaptations” ( Buss, 2019 , p. 42). The numerous mechanisms recruited in romantic love, the large number of psychological characteristics, and the multiple functions it serves suggest that romantic love may be an amalgamation of numerous adaptations that respond to a variety of adaptive challenges. However, while romantic love may comprise several inter-related adaptations, this does not preclude the possibility that some components are by-products. A by-product is a trait that evolved “not because it was selectively advantageous, but because it was inextricably linked…to another trait that was reproductively advantageous” ( Andrews et al., 2002 , p. 48).

Health-promoting benefits of romantic love, such as elevated mood, increased sleep quality, and up-regulated immune responses, for example, may be by-products of mood circuitry (see Nettle and Bateson, 2012 ; D’Acquisto, 2017 ; Jahangard et al., 2017 ) or other mechanisms, even though they offer some survival or reproductive advantage. Elevated mood, better sleep quality, and an associated up-regulated immune system probably evolved prior to the emergence of romantic love (see Flajnik and Kasahara, 2010 ; Loonen and Ivanova, 2015 ). As a result, it might be prudent to contend that romantic love is a complex suite of adaptations and by-products.

Further, while the evidence points to romantic love as a suite of adaptations and by-products, it is not adaptive in every context. Romantic love continues to have its reproduction-promoting functions in the modern world in some circumstances, either by immediately promoting reproduction, or indirectly promoting reproduction via the formation of romantic relationships, the members of which later reproduce. To that extent, romantic love is sometimes adaptive (see Laland and Brown, 2011 , for distinction between “adaptation” and “adaptive” and lists of benefits, above, for examples of how romantic love can be adaptive). There are circumstances when romantic love may be maladaptive, however, as is evidenced by the substantial fitness-relevant costs of romantic love detailed above. Cogent examples of this are when a loved one is already in a committed relationship or otherwise not interested, when an individual engages in obsessive pursuit that can have social or even legal ramifications, or when violence ensues.

When applied to romantic love, the fourth of Tinbergen’s (1963) four questions asks, “What is the evolutionary history of romantic love?” Phylogenetic explanations focus on the origin and maintenance of a trait in historical evolutionary terms ( Tinbergen, 1963 ; Bateson and Laland, 2013 ). They put a biological trait in a comparative perspective by focusing on the presence or absence of the trait in closely, and sometimes more distantly, related species. In this section, we describe the theory of independent emotion systems and articulate a theory of co-opting mother-infant bonding mechanisms. We examine the primitive structures related to romantic love that arose in our mammalian evolutionary past and were restructured in pair-bonded species. We also examine the particular history of pair-bonds, and thus romantic love, in hominin evolution, with a comparison to other species of primates, especially apes. Finally, we examine the effect of gene-cultural evolutionary issues with regard to romantic love.

Independent Emotion Systems

Fisher’s ( 1998 , 2000 , see also Fisher et al., 2002 ) evolutionary theory of independent emotions systems delineates sex drive (lust), attraction (romantic love), and attachment (pair-bonds). Sex drive is primarily associated with estrogens and androgens and serves to motivate individuals to engage in sexual activity, generally. Attraction is primarily associated with the catecholamines (i.e., dopamine and norepinephrine), phenylethylamine, and serotonin and serves to focus efforts on preferred mating partners. Attachment is primarily associated with oxytocin and vasopressin and serves to enable individuals to engage in positive social behaviors and connections of a sufficient length of time to satisfy species-specific parenting approaches ( Fisher, 1998 ). Sex drive relates most to the sex function of romantic love, attraction to the mate choice and courtship functions, and attachment to the pair-bonding function. Romantic love shares similarities with the ‘courtship attraction system’ found in many mammals ( Fisher et al., 2006 ).

Co-opting Mother Infant Bonding Mechanisms

While the theory of independent emotion systems ( Fisher, 1998 , 2000 ; Fisher et al., 2002 ) has been the predominate theoretical account of the evolution of romantic love for more 20 years, comparative studies, imaging studies, and assessments of psychological characteristics have raised the possibility of a complimentary evolutionary theory, that of co-opting mother-infant bonding mechanisms. Literature on romantic love, maternal love (of which mother-infant bonding is a part), mother–infant bonding, and pair-bonding ( Bartels and Zeki, 2004 ; Ortigue et al., 2010 ; Numan and Young, 2016 ; Walum and Young, 2018 ) suggests romantic love may have evolved by co-opting mother-infant bonding mechanisms. Co-option is an evolutionary process whereby a trait (e.g., mechanism, morphology, behavior) is repurposed – that is, it serves a different function to that which it originally served (see McLennan, 2008 ).

Animal research, focusing on mammals, and involving, monogamous prairie voles, finds substantial similarities between mother-infant bonding mechanisms and pair-bonding mechanisms ( Numan and Young, 2016 ). “[A]mygdala and nucleus accumbens–ventral pallidum (NA–VP) circuits are involved in both types of bond formation, and dopamine and oxytocin actions within NA appear to promote the synaptic plasticity that allows either infant or mating partner stimuli to persistently activate NA–VP attraction circuits, leading to an enduring social attraction and bonding” ( Numan and Young, 2016 , p. 98). Some of these circuits do not appear to be involved in human romantic love, but there are other similarities that support a theory of co-opting mother-infant bonding in humans.

Several brain regions implicated in romantic love overlap precisely with that involved in maternal love. This includes activity in numerous regions that are associated with a high density of oxytocin and vasopressin receptors ( Bartels and Zeki, 2000 , 2004 ) although it should be noted that in the study that asserts this, participants included mothers experiencing maternal love beyond the mother-infant bonding stage. A meta-analysis of love also found romantic and maternal love shared activity in dopamine-rich areas ( Ortigue et al., 2010 ). Almost nothing is known about the mechanisms regulating the infant side of mother-infant bonding. However, some inferences have been made from animal models which suggest that the mechanisms may be similar to those regulating the maternal side, but without involvement of the amygdala (see Sullivan et al., 2011 , for review).

There are substantial psychological similarities between romantic love and early parental love, of which mother–infant bonding is a part. Extreme similarities exist between romantic love and early parental love in the domains of altered mental state, longing for reciprocity, idealization of the other, and dichotomous resolution of the establishment of intimate mutually satisfying reciprocal patterns of interaction usually marked by a culturally defined ritual ( Leckman and Mayes, 1999 ). Similar trajectories of preoccupation in romantic love and parental love also exist. In romantic love, preoccupation increases through the courtship phase and peaks at the point of reciprocity where preoccupation begins to slowly diminish. In parental love, preoccupation increases throughout pregnancy and peaks at the point of birth where preoccupation begins to diminish.

Mammalian Antecedents

Romantic love in humans is caused by physiological mechanisms whose evolutionary roots were planted in our early mammalian ancestors. These evolutionary roots provided the raw materials that were fleshed out, in evolutionary time, to form the basis of a wide range of social behaviors in mammals, including those related to sex drive, mate choice, and attachment ( Fisher, 1998 , 2000 ; Fisher et al., 2002 ; Broad et al., 2006 ; Carter and Perkeybile, 2018 ; Curley and Keverne, 2005 ; Fisher et al., 2006 ; Fischer et al., 2019 ; Johnson and Young, 2015 ; Numan and Young, 2016 ; Porges, 1998 ). Romantic love may have evolved after the neural circuitry associated with mate choice became populated by oxytocin receptors which played a role in the evolution of enduring social attraction and pair-bond formation (see Numan and Young, 2016 ). “[P]air bonding is the evolutionary antecedent of romantic love and…the pair bond is an essential element of romantic love” ( Walum and Young, 2018 , p. 12).

Examining the similarities between the neurobiological and endocrinological mechanisms involved in mother-infant bonding and pair-bonding in mammals, it becomes apparent that the maternal functions of this suite of adaptations arose deep in the evolutionary history of mammals ( Numan and Young, 2016 ). Their derived, pair-bonding functions would have arisen later in a very small number of species (only 3–5% pair-bond). As such, the neural circuitry and other proximate mechanisms involved in mother-infant bonding in mammals “may have provided a primordial neural scaffold upon which other types of strong social bonds, such as pair bonds, have been built” ( Numan and Young, 2016 , p. 99). We are, thus, on reasonably solid ground to posit evolutionary trajectories of romantic love. Figure 1 presents information and hypotheses about the evolutionary history of romantic love. Evolutionary trajectories of romantic love start with the ancestral mammalian mother–infant bonding mechanisms and culminate in their co-option and modification for pair-bonding in several mammalian lineages ( Numan and Young, 2016 ). Human romantic love results from one of these trajectories. In another trajectory—the one that includes pair-bonding prairie voles ( Microtus ochrogaster )—we know quite a lot about the functioning of oxytocin, vasopressin, and dopamine in facilitating pair-bonding (e.g., Carter and Getz, 1993 ; Carter and Perkeybile, 2018 ; Walum and Young, 2018 ). Although these derived changes to the primitive mammalian machinery may not be the direct evolutionary antecedents of those at work in humans (they are, rather, the product of parallel evolution), they provide a window into how basic machinery can be modified to affect those ends. One substantive difference appears to be the relative importance of the hormonal drivers in the smaller species, and the dopamine-related ones in humans ( Broad et al., 2006 ; Fisher et al., 2016 ).

Phylogenetic relationships among select mammal species that pair-bond.

Pair-Bonds in Primates

Humans are members of the primate superfamily Anthropoidea, amongst whom there is great diversity in social systems, and whose ancestral state likely included complex group-based social relationships ( Kay et al., 1997 ; Shultz and Dunbar, 2007 ). This would have included long-term association between unrelated males and females—which is a far cry from the solitary system that is modal and ancestral for mammals ( Lukas and Clutton-Brock, 2013 ; Opie et al., 2013 ). There are even some members of this lineage who have evolved pair-bonds, such as the marmosets and tamarins (Callitrichidae), and gibbons (Hylobatidae). The similarities between these species and humans in terms of the adaptive suite related to pair-bonds, like the similarities between humans and voles, are due to convergent/parallel evolution ( French et al., 2018 ).

Our closest living relatives are the common chimpanzee ( Pan troglodytes ) and bonobo ( Pan paniscus ) with whom we share a common ancestor just 5–8 million years ago. While bonobos are alluring due to their free-willed sexual nature, common chimpanzees provide a better glimpse into the behavior of our direct ancestors. Although the common chimpanzee mating system is defined as promiscuous, there are, in fact, three forms of common chimpanzee mating tactics ( Morin, 1993 ). The first two—possessive mating and consortships—involve some of the characteristics we associate with romantic love, such as a more-than-fleeting association and mate guarding, but they are much rarer than the third type, opportunistic mating. The comparison of chimpanzees and humans, thus, suggests that one possible hypothesis for the emergence of romantic love is that it originated in their common ancestor (H1 in Figure 1 ). Alternatively, it might be that the common ancestor had an adaptive repertoire that was primed for its emergence when the requisite socioecological context arose. In this way, the evolution of romantic love from chimp-like mating is similar to the evolution of human culture from chimp-like culture.

For some, the origin of romantic love was more likely to have fallen somewhere on our side of the human–chimpanzee split (e.g., Fisher et al., 2016 ). Even so, we are left with the difficulty of pinpointing exactly when it arose—attributable to there being only one extant hominin species from amongst the many that have existed ( Pigliucci and Kaplan, 2006 ) and the lack of direct fossil evidence for romantic love. If we accept the conventional view that romantic love evolved to facilitate pair-bonding, then we can search for clues about the evolution of the former by tracing the evolution of the latter ( Fletcher et al., 2015 ). A transition from ape-like to human-like sexual behavior in our lineage may have pre-dated the emergence of the genus Homo ( Lovejoy, 1981 )—and, thus, we have a second hypothesis (H2 in Figure 1 ). A comparison of sexual dimorphism in Australopithecus and early genus Homo , however, suggests a third hypothesis—that it arose after their emergence (H3 in Figure 1 ). Several lines of evidence suggest that the earliest members of our species, Homo sapiens , pair-bonded but were not necessarily monogamous. Based on an examination of the distribution of mating systems in modern, small-scale human societies and three correlates of primate mating systems ( Dixson, 2009 ), it is possible to conclude that pair-bonds are a “ubiquitous” feature of human mating that can manifest through polygyny or polyandry, but most commonly occur in the form of serial monogamy ( Schacht and Kramer, 2019 ). The final hypothesis, thus, is that romantic love is the unique domain of our species (H4 in Figure 1 ).

The transition to mostly monogamous and some polygynous groupings could have had a transitional phase where polygynous groupings were the norm ( Chapais, 2008 , 2013 ). Pair-bonds may have arisen from a complex interaction between the fitness benefits and costs of mating and parental care ( Quinlan, 2008 ). The transition from ape-like promiscuity to human pair-bonds may have been driven by the provision of females by low-ranking males ( Gavrilets, 2012 ). The direct benefits for females was the food provided, for the males, the mating opportunity. This may have led to selection for males that were less aggressive and more prosocial. The female mate-choice mechanism is a distinct possibility for explaining human self-domestication ( Gleeson and Kushnick, 2018 ).

Gene-Culture Coevolution

Romantic love is a universal or near-universal feature in human societies ( Jankowiak and Fischer, 1992 ; Gottschall and Nordlund, 2006 ; Jankowiak and Paladino, 2008 ; Fletcher et al., 2015 ; Buss, 2019 ; Sorokowski et al., 2020 ). A small number of genetic correlation studies show that there are a number of genes associated with romantic love ( Emanuele et al., 2007 ; Murray et al., 2019 ; Acevedo et al., 2020 ). Other insights into the genetic evolution of romantic love can be garnered from elsewhere, however. For example, life history theory provides insight into ethnic or geographical variation in romantic love and its role in providing sexual access by women.

Romantic love is among the most common reasons female adolescents give for having sex ( Ozer et al., 2003 ). A “slow” life history strategy is associated with eros more than other loving styles ( Marzec and Łukasik, 2017 ). Psychopathology associated with impulsivity is a feature of a “fast” life history strategy, as is promiscuous sexuality ( Del Giudice, 2016 ). Greater impulsivity is associated with a reduced likelihood of giving romantic love as a reason for having sex among adolescent females ( Dawson et al., 2008 ).

As a result, genetic determinants of life history strategies (e.g., Figueredo et al., 2004 ) may influence the occurrence of romantic love. National scores on the life history strategy genetic factor index correlate with adolescent fertility rates indicating that genetic predictors of a fast life history are associated with higher rates of adolescent pregnancy ( Luoto, 2019b ). This ethnic or geographical variation in the genetic determinants of life history strategies may also represent ethnic or geographic variation in the genetic determinants and reproductive relevance of romantic love.

In addition to this, cultural factors may have affected the role of romantic love in mating and marriage decisions—and this has implications for understanding the evolution of romantic love ( Fletcher et al., 2015 ). Arranged marriages are the norm in 80% of 200 forager societies from the Ethnographic Atlas ( Apostolou, 2007 ). Phylogenetic methods to reconstruct the ancestral marriage patterns of our species using the same data found that there were likely marriage transactions (brideprice or brideservice) but only a limited amount of polygyny ( Walker et al., 2011 ). While the ancestral state for arranged marriages was not definitive, arranged marriages were likely present around 50 thousand years ago, when our ancestors expanded their range beyond Africa. So, despite romantic love being viewed as an important component of marriage and mating, it may have played a role of decreasing importance in the recent evolutionary history of our species. Arranged marriages may have limited the role of female mate choice in intersexual selection ( Apostolou, 2007 ). Further, despite romantic love’s decreased role in courtship and marriage, it may have continued to serve a role in facilitating pair-bonding as romantic love can develop even in the arranged-marriage context. The role of romantic love in facilitating mate choice, courtship, and marriage may now be increasing with the decline and modification of arranged marriages in many parts of the world (e.g., Allendorf and Pandian, 2016 ). This may be the result of the increasing sexual equality of women (e.g., de Munck and Korotayev, 1999 ).

Romantic love is a complex and multifaceted aspect of human biology and psychology. Our approach in this review has been to highlight how Tinbergen’s (1963) “four questions” can help us to synthesize the important strands related to the mechanisms, development, fitness-relevant functions, and evolutionary history of this phenomenon. Here, we synthesize what this review has presented in each level of explanation and suggest what this indicates about other levels of explanation. We then highlight some gaps in our knowledge that could be filled with future research and present a new ethologically informed working definition of romantic love.

What Do Tinbergen’s Four Questions Tell Us?

One of the benefits of using Tinbergen’s four questions as a framework to describe a complex trait such as romantic love is its ability for one level of explanation to provide insights into the other level of explanation (see Tinbergen, 1963 ; Bateson and Laland, 2013 ; Zietsch et al., 2020 ). In particular, an understanding of the proximate causes of romantic love has provided insights into the functions and phylogeny of romantic love although an understanding of the ultimate level of explanation provides some insights into the mechanisms of romantic love.

Multiple mechanistic systems involved in romantic love suggests it may serve multiple functions and may be a suite of adaptations and by-products rather than a single adaptation. We found that romantic love is associated with activity in a number of neural systems: reward and motivation, emotions, sexual desire and arousal, and social cognition. It is also associated with activity in higher-order cortical brain areas that are involved in attention, memory, mental associations, and self-representation. We also found that romantic love is associated with a number of endocrine systems: sex hormones, serotonin, dopamine, oxytocin, cortisol, and nerve growth factor. This is consistent with our position that romantic love serves mate choice, courtship, sex, and pair-bonding functions. Reward and motivation system activity may be particularly involved in the mate choice function of romantic love. Cortisol may be particularly indicative of the courtship function of romantic love, which overlaps with pair-bonding. Neural areas associated with sexual desire and arousal and the activity of sex hormones may play a particular role in the sex function. Finally, reward and motivation regions of the brain (rich with oxytocin receptors) and activity of the oxytocin system may play a particular role in the pair-bonding function of romantic love. Our understanding of the biological mechanisms that cause romantic love supports our description of romantic love’s functions.

Mechanistic similarities between romantic love and mother-infant bonding suggest that romantic love may have evolved by co-opting mother-infant bonding mechanisms. This articulates one hypothesis about the evolutionary history of romantic love that complements the predominate theory of independent emotion systems ( Fisher, 1998 , 2000 ; Fisher et al., 2002 ). This is supported by the psychological similarities between romantic love and early parental love.

Evidence of substantial activity of oxytocin receptor rich brain regions and the oxytocin endocrine system in romantic love lends weight to the position that romantic love only evolved after the neural circuitry associated with mate choice, specifically, regions of the mesolimbic reward pathway and dopamine rich areas, became populated by oxytocin receptors specifically receptive to stimuli from mating partners. That played a role in the evolution of enduring social attraction and pair-bond formation ( Numan and Young, 2016 ). This supports our claim that romantic love probably evolved in conjunction with pair-bonds in humans. As a result, we are bolstered when we contend that romantic love emerged relatively recently in the history of humans.

The duration of romantic love also raises questions about the functions of romantic love. It has been said that the psychological features of romantic love can last from 18 months to 3 years in reciprocated romantic love. However, in our evolutionary history, romantic love would have usually occurred in the context of pregnancy and child birth. Mother-infant bonding becomes active around the time of childbirth. We are not aware of any research that has investigated whether romantic love can occur at the same time as mother-infant bonding or whether it must subside for mother-infant bonding to become active. Answering this question would elucidate if the functions of romantic love extinguish once reproduction has been successful. The existence of long-term romantic love also raises questions about the functions of romantic love. It has been posited that long-term romantic love is “part of a broad mammalian strategy for reproduction and long-term attachment” ( Acevedo et al., 2020 , p. 1). This may indicate that long-term romantic love serves similar functions to romantic love that lasts a shorter period of time.

Just as the multiple biological mechanisms involved in romantic love suggests a variety of functions, the functions of romantic love specified in our review suggests specific biological mechanisms are involved. As outlined above, specific functions may be associated with specific mechanisms and this should be an area of targeted research.

The possibility of romantic love evolving by co-opting mother-infant bonding mechanisms raises a number of possibilities in relation to the proximate causes of romantic love. It suggests that social activity associated with mother–infant bonding (e.g., filling of needs, specific cues) may be particularly important precursors to, or features of, romantic love. It suggests that many of the genes and polymorphisms involved in causing romantic love may have been present in mammals since the emergence of mother–infant bonding, making comparative animal research using mammals relevant. It also suggests that further research into shared neural activity between romantic love and mother–infant bonding is warranted.

We contend that romantic love probably emerged in conjunction with pair-bonds in humans or human ancestors. As such, further information about the similarities and differences between romantic love (pair-bonding) and companionate love (established pair-bonds) is needed. In particular, information about any role of the mesolimbic pathway (see Loth and Donaldson, 2021 ) or regions associated with sexual desire in companionate love would help to shed light on the evolutionary history of pair-bonding and pair-bonds. Specifically, this could shed light on if, as has been suggested (see Walum and Young, 2018 ), romantic love and pair-bonds are inextricably linked.

Areas of Future Research

One issue with research into the mechanisms of romantic love is that it has, with some exceptions (e.g., Fisher et al., 2010 ), utilized samples of people experiencing romantic love who are in a relationship with their loved one. Romantic love serves a mate choice and courtship function, and as a result, a large proportion of people experiencing romantic love are not in a relationship with their loved one (e.g., Bringle et al., 2013 ). A small number of studies have directly investigated unrequited love (e.g., Tennov, 1979 ; Baumeister et al., 1993 ; Hill et al., 1997 ; Aron et al., 1998 ; Bringle et al., 2013 ), but none of these investigated the mechanisms that cause romantic love. Studying such people might identify the specific contributions of particular mechanisms to particular functions. For example, the mechanisms associated with the pair-bonding function of romantic love may not be active in individuals who are engaging in courtship and the mechanisms involved in courtship may not be present in lovers who are already in a relationship with their loved one. Research would benefit from considering the mechanisms that underlie related psychopathologies and it would be useful to understand the relationship between mate preferences and romantic love.

Molecular genetics research, such as that undertaken by Acevedo et al. (2020) , could further identify contributions of genes in people experiencing romantic love. Resting state fMRI provide an opportunity to investigate networks characteristic of psychopathology related to romantic love. Research should investigate the automatic/internal emotional regulatory network and the volitional/external regulatory network associated with mania/hypomania in people experiencing romantic love. Further research is required into the endocrinology of romantic love. In particular, further research is needed into the role of opioids, corticotropin-releasing factor, glutamate, acetylcholine, and vasopressin in romantic love. Efforts should be made to combine psychological and mechanisms research. For example, differences in neural or endocrine activity may be present in people experiencing romantic love who display elevated symptoms of depression compared to those who display reduced symptoms. As a result, neuroimaging and endocrinological studies could categorize people experiencing romantic love according to their levels of depression or type of hypomanic symptoms.

Given the large number of fMRI studies, interpreting the neuroimaging literature can be overwhelming. It has been nearly 10 years since the last meta-analysis of fMRI studies including romantic love. It is time for another one that focuses solely on romantic love. There is also a pressing need to attempt to replicate and extend endocrine studies and to specifically investigate the oxytocin system in people experiencing romantic love using validated measures of romantic love. As with many areas of psychological research ( Henrich et al., 2010 ), and specifically in areas related to mating psychology ( Apicella et al., 2019 ; Scelza et al., 2020 ), there is a pressing need to ensure that samples used in research are not exclusively Western, educated, industrialized, rich, and democratic.

Limited ontogeny research has elucidated the mechanisms causing romantic love across the lifespan. The literature that has (e.g., Luoto, 2019a ), has focused on mate choice, rather than romantic love, per se . We know nothing about the neurobiology or endocrinology of romantic love in children or about the endocrinology of long-term romantic love. It would be useful to investigate how the functions of romantic love differ according to age of individuals or the duration of romantic love. Internal and external factors influence romantic love, although there has been surprisingly little research into this topic. It would be prudent to continue to develop a more detailed understanding of the factors that lead to romantic love (e.g., Riela et al., 2010 , 2017 ). It would be useful to better understand the relationship between attachment styles and romantic love. Research should investigate if romantic love can occur at the same time as mother-infant bonding, or if they are mutually exclusive states.

Research into the functions of romantic love is sparse. There is a need for clear, evidence-informed definitions and descriptions of each of the functions of romantic love. It is likely that different mechanisms moderate different functions, and research should attempt to determine the contribution of specific genetic, neural, and endocrine activity to each individual function (see Zietsch et al., 2020 ). The advent of contraception and the adoption of family planning strategies means romantic love now serves more of a sex function than a pregnancy function in some environments. This is particularly the case early in a relationship. Pregnancy may become a feature as a relationship progresses and the fitness consequences of romantic love need to be investigated. Romantic love’s role as a suite of adaptations and by-products should be investigated. There is theoretical support for the notion that romantic love serves a health-promoting function (e.g., Esch and Stefano, 2005 ); however, there is a limited number of studies demonstrating a health-promoting effect of romantic love.

The relative infancy of genetic research, the lack of a clear fossil record, and the small number of species with which comparative analysis can be undertaken, means novel and creative means of investigating the phylogeny of romantic love must be undertaken. There is a need to pin-point the phylogenetic emergence of romantic love and the factors that caused it. To do this, more research into the genetics of romantic love must be conducted, and this should consider the phylogeny of specific genes and polymorphisms (e.g., Acevedo et al., 2020 ; see also Walum and Young, 2018 ). Efforts to assess the contribution of sexual selection to the evolution of romantic love are warranted. Studies of newly discovered fossils can help to identify shifts in sexual dimorphism that are indicative of pair-bonds. Further observational and experimental research into romantic love in hunter-gatherer tribes could tell us more about how romantic love functioned in our evolutionary history. Comparative research still has much to contribute. Research should explore the possibility that initial changes to the ancestral mammalian physiology that led directly to human romantic love arose in response to selection on both mating and non-mating-related behavior, such as pro-sociality (e.g., Barron and Hare, 2020 ; Luoto, 2020 ) or unique aspects of our species’ parenting repertoire. It might be fruitful to further investigate the relationship between romantic love and life history theory (e.g., Olderbak and Figueredo, 2009 ; Marzec and Łukasik, 2017 ). Finally, efforts should be made to elaborate and test the theory that romantic love emerged by co-opting mother–infant bonding mechanisms.

A New Working Definition of Romantic Love

The introduction to this review provided four definitions or descriptions of romantic love. For decades, most definitions ( Hendrick and Hendrick, 1986 ; Sternberg, 1986 ; Hatfield and Rapson, 1993 ) of romantic love have informed research into the cognitive, emotional, and behavioral characteristics of romantic love. The past two decades, however, have seen an increasing focus on the biology of romantic love. Only recently has an evolution-informed definition been proposed ( Fletcher et al., 2015 ). That working definition, however, does not incorporate much of the research that provides insight into the proximate and ultimate causes of romantic love.

We believe that the analytical approach taken in this review has identified sufficient information to justify the development of a new ethologically informed working definition of romantic love. The purpose would be to create an inclusive definition that is useful for researchers in varied disciplines investigating romantic love’s psychological characteristics, genetics, neurobiology, endocrinology, development, fitness-relevant functions, and evolutionary history. It may also be of use to psychologists and psychiatrists attempting to understand the experience and etiology of romantic love in their practice. It should be sufficiently precise and descriptive to both guide and link research. We provide, here, a working definition of romantic love:

• Romantic love is a motivational state typically associated with a desire for long-term mating with a particular individual. It occurs across the lifespan and is associated with distinctive cognitive, emotional, behavioral, social, genetic, neural, and endocrine activity in both sexes. Throughout much of the life course, it serves mate choice, courtship, sex, and pair-bonding functions. It is a suite of adaptations and by-products that arose sometime during the recent evolutionary history of humans.

We situate the study of romantic love within the context of existing human mating literature. Our definition recognizes that romantic love is experienced across the lifetime of an individual, that research has shed light on the social, psychological, genetic, neural, and endocrine characteristics associated with it, and that it occurs in both sexes. Our definition also recognizes that romantic love serves a variety of functions and that these functions may vary across the lifespan. It does not exclude long-term or unrequited romantic love from the definition. Health is not identified as a function of romantic love in our definition despite being considered in our review. If more evidence comes to light, this definition can be amended to incorporate health.

Our definition has similarities and differences with the definition proposed by Fletcher et al. (2015) . This is appropriate given both are informed by evolutionary approaches which differ somewhat. We do not specifically define romantic love as being a commitment device or reference passion, intimacy, and caregiving. In our review, we recognize that romantic love is a commitment device and serves to display commitment and signal fidelity as part of its courtship function. We believe that reference to romantic love’s behavioral activity and courtship and pair-bonding functions sufficiently encapsulate this concept. Sternberg’s (1997) definition of romantic love and Fletcher et al.’s (2015) definition include references to passion and intimacy. Caregiving (e.g., provision of psychological and emotional resources, sharing resources), while associated with pair-bonding, is not sufficiently definitive of romantic love using Tinbergen’s four questions as a framework to include in our definition.

We do not reference the universality of romantic love. While some experts assert its universality (e.g., Fletcher et al., 2015 ; Buss, 2019 ), we believe that the finding of Jankowiak and Fischer (1992) leaves enough uncertainty for it to be prudent to omit this aspect from our definition. Their research has found no evidence of romantic love in fifteen cultures (see Jankowiak and Paladino, 2008 , for update to the original investigation) although this is probably the result of lack of data rather than evidence to the contrary. Once this matter is settled, which could be achieved by further investigating those societies where no evidence of romantic love was found, the definition can be amended. Fletcher et al. (2015) state that romantic love is associated with pair-bonds. We do the same by stating that pair-bonding is one of the functions of romantic love.

We also do not make specific reference to romantic love suppressing the search for mates. We recognize this as a cost in our review, but do not believe that this is so definitive of romantic love to include in our definition. Rather, we believe that our reference to “behavioral” activity and the “mate choice” function of romantic love in our definition sufficiently accommodates this feature. Our definition provides more detail than that provided by Fletcher et al. (2015) by including elements derived from substantial research into the mechanisms, ontogeny, functions, and phylogeny of romantic love. Like the Fletcher et al. (2015) definition, our definition recognizes that romantic love has distinct psychological characteristics and that we know about some of the proximate mechanisms that regulate it. However, as explained above, we do not include reference to the health-promoting effects of romantic love.

As more information about romantic love is gathered, we anticipate the definition to develop. However, we believe that this definition is an improvement upon previous definitions and adequately captures what is currently known about romantic love’s proximate and ultimate causes. It would be useful for researchers investigating romantic love from myriad perspectives. This definition should be critiqued and improved, and we welcome any such efforts from researchers and theorists across the spectrum of academic disciplines.

Our review provides a comprehensive account of the phenomenon known as romantic love. It covers topics such as social precipitants, psychology, genetics, neurobiology, and endocrinology. It provides an account of romantic love across the lifetime of an individual and is the first to propose four discrete reproduction-related functions of romantic love supported in the literature: mate choice, courtship, sex, and pair-bonding. It provides a summary of the benefits and costs of romantic love, outlines possible selective pressures, and posits that it is a complex suite of adaptations and by-products. We propose four potential evolutionary histories of romantic love and introduce the theory of co-opting mother-infant bonding mechanisms. We have identified a number of specific and general areas for future research. Our review suggests a new, ethologically informed working definition of romantic love that synthesizes a broad range of research. The working definition we propose serves to define a complex trait in a way that can both guide and link research from a variety of fields.

Author Contributions

AB conceived the manuscript. AB and GK collaborated on the development of the analytical framework and writing of the manuscript. Both authors approved the final version.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

We would like to thank the reviewers for comments that helped to improve the manuscript.

Supplementary Material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fpsyg.2021.573123/full#supplementary-material

• Abler B., Greenhouse I., Ongur D., Walter H., Heckers S. (2008). Abnormal reward system activation in mania. Neuropsychopharmacology 33 2217–2227. 10.1038/sj.npp.1301620 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Acevedo B. P., Aron A. (2009). Does a long-term relationship kill romantic love? Rev. Gen. Psychol. 13 59–65. 10.1037/a0014226 [ CrossRef ] [ Google Scholar ]
• Acevedo B. P., Aron A., Fisher H. E., Brown L. L. (2012). Neural correlates of long-term intense romantic love. Soc. Cogn. Affect. Neurosci. 7 145–159. 10.1093/scan/nsq092 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Acevedo B. P., Poulin M. J., Collins N. L., Brown L. L. (2020). After the honeymoon: neural and genetic correlates of romantic love in newlywed marriages. Front. Psychol. 11 : 634 . 10.3389/fpsyg.2020.00634 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Adolphs R. (2001). The neurobiology of social cognition. Curr. Opin. Neurobiol. 11 231–239. 10.1016/s0959-4388(00)00202-6 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Aktipis A., Cronk L., Alcock J., Ayers J. D., Baciu C., Balliet D., et al. (2018). Understanding cooperation through fitness interdependence. Nat. Hum. Behav. 2 429–431. 10.1038/s41562-018-0378-4 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Allendorf K., Pandian R. K. (2016). The decline of arranged marriage? Marital change and continuity in India. Popul. Dev. Rev. 42 435–464. 10.1111/j.1728-4457.2016.00149.x [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Aloe L., Rocco M. L., Balzamino B. O., Micera A. (2015). Nerve growth factor: a focus on neuroscience and therapy. Curr. Neuropharmacol. 13 294–303. 10.2174/1570159x13666150403231920 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Andersson M., Simmons L. W. (2006). Sexual selection and mate choice. Trends Ecol. Evol. 21 296–302. 10.1016/j.tree.2006.03.015 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Andrews P. W., Gangestad S. W., Matthews D. (2002). Adaptationism - how to carry out an exaptationist program. Behav. Brain Sci. 25 489–504. [ PubMed ] [ Google Scholar ]
• Apicella C., Norenzayan A., Henrich J. (2019). Beyond WEIRD: a review of the last decade and a look ahead to the global laboratory of the future. Evol. Hum. Behav . 41 319–329. 10.1016/j.evolhumbehav.2020.07.015 [ CrossRef ] [ Google Scholar ]
• Apostolou M. (2007). Sexual selection under parental choice: the role of parents in the evolution of human mating. Evol. Hum. Behav. 28 403–409. 10.1016/j.evolhumbehav.2007.05.007 [ CrossRef ] [ Google Scholar ]
• Arnold A. P. (2020). Sexual differentiation of brain and other tissues: five questions for the next 50 years. Horm. Behav. 120 104691 . 10.1016/j.yhbeh.2020.104691 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Aron A., Aron E. N., Allen J. (1998). Motivations for unreciprocated love. Pers. Soc. Psychol. Bull. 24 787–796. 10.1177/0146167298248001 [ CrossRef ] [ Google Scholar ]
• Aron A., Dutton D. G., Aron E. N., Iverson A. (1989). Experiences of falling in love. J. Soc. Pers. Relationsh. 6 243–257. 10.1177/0265407589063001 [ CrossRef ] [ Google Scholar ]
• Aron A., Fisher H., Mashek D. J., Strong G., Li H. F., Brown L. L. (2005). Reward, motivation, and emotion systems associated with early-stage intense romantic love. J. Neurophysiol. 94 327–337. 10.1152/jn.00838.2004 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Aron A., Tomlinson J. M. (2019). “Love as expansion of the self ,” in The New Psychology of Love ,eds. Sternberg R. J., Sternberg K. 2nd Edn (United Kingdom: Cambridge University Press; ), 1–24. 10.1017/9781108658225.002 [ CrossRef ] [ Google Scholar ]
• Ayano G. (2016). Dopamine: receptors, functions, synthesis, pathways, locations and mental disorders: review of literatures. J. Ment. Disord. Treat. 2 120–124. [ Google Scholar ]
• Bajoghli H., Farnia V., Joshaghani N., Haghighi M., Jahangard L., Ahmadpanah M., et al. (2017). “I love you forever (more or less)” - stability and change in adolescents’ romantic love status and associations with mood states. Rev. Brasil. Psiquiatr. 39 323–329. 10.1590/1516-4446-2016-2126 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Bajoghli H., Joshaghani N., Gerber M., Mohammadi M. R., Holsboer-Trachsler E., Brand S. (2013). In Iranian female and male adolescents, romantic love is related to hypomania and low depressive symptoms, but also to higher state anxiety. Int. J. Psychiatry Clin. Pract. 17 98–109. 10.3109/13651501.2012.697564 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Bajoghli H., Joshaghani N., Mohammadi M. R., Holsboer-Trachsler E., Brand S. (2011). In female adolescents, romantic love is related to hypomanic-like stages and increased physical activity, but not to sleep or depressive symptoms. Int. J. Psychiatry Clin. Pract. 15 164–170. 10.3109/13651501.2010.549340 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Bajoghli H., Keshavarzi Z., Mohammadi M. R., Schmidt N. B., Norton P. J., Holsboer-Trachsler E., et al. (2014). “I love you more than I can stand!” - romantic love, symptoms of depression and anxiety, and sleep complaints are related among young adults. Int. J. Psychiatry Clin. Pract. 18 169–174. 10.3109/13651501.2014.902072 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Barron A. B., Hare B. (2020). Prosociality and a sociosexual hypothesis for the evolution of same-sex attraction in humans. Front. Psychol. 10 : 2955 . 10.3389/fpsyg.2019.02955 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Bartels A., Zeki S. (2000). The neural basis of romantic love. Neuroreport 11 3829–3834. 10.1097/00001756-200011270-00046 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Bartels A., Zeki S. (2004). The neural correlates of maternal and romantic love. Neuroimage 21 1155–1166. 10.1016/j.neuroimage.2003.11.003 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Bateson P., Laland K. N. (2013). Tinbergen’s four questions: an appreciation and an update. Trends Ecol. Evol. 28 712–718. 10.1016/j.tree.2013.09.013 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Baumeister R. F., Wotman S. R., Stillwell A. M. (1993). Unrequited love - on heartbreak, anger, guilt, scriptlessness, and humiliation. J. Pers. Soc. Psychol. 64 377–394. 10.1037/0022-3514.64.3.377 [ CrossRef ] [ Google Scholar ]
• Baumgarten H. G., Grozdanovic Z. (1998). Role of serotonin in obsessive-compulsive disorder. Br. J. Psychiatry Suppl. 35 13–20. [ PubMed ] [ Google Scholar ]
• Bear A., Rand D. G. (2019). Can strategic ignorance explain the evolution of love? Top. Cogn. Sci. 11 393–408. 10.1111/tops.12342 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Belujon P., Grace A. A. (2017). Dopamine system dysregulation in major depressive disorders. Int. J. Neuropsychopharmacol. 20 1036–1046. 10.1093/ijnp/pyx056 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Berry A., Bindocci E., Alleva E. (2012). - NGF, brain and behavioral plasticity. - 2012. Neural Plast. 2012 : 784040 . [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Bindl U. K., Parker S. K., Totterdell P., Hagger-Johnson G. (2012). Fuel of the self-starter: how mood relates to proactive goal regulation. J. Appl. Psychol. 97 134–150. 10.1037/a0024368 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Bowers R. I., Place S. S., Todd P. M., Penke L., Asendorpf J. B. (2012). Generalization in mate-choice copying in humans. Behav. Ecol. 23 112–124. 10.1093/beheco/arr164 [ CrossRef ] [ Google Scholar ]
• Bowlby J. (1969). Attachment and Loss: Attachment , Vol. 1 . New York, NY: Basic Books. [ Google Scholar ]
• Bowlby J. (1973). Attachment and Loss: Separation: Anxiety and Anger. New York, NY: Basic Books. [ Google Scholar ]
• Bowlby J. (1980). Attachment and Loss: Loss , Vol. 3 . New York, NY: Basic Books. [ Google Scholar ]
• Brand S., Foell S., Bajoghli H., Keshavarzi Z., Kalak N., Gerber M., et al. (2015). “Tell me, how bright your hypomania is, and I tell you, if you are happily in love!”-among younlove!”-among young adults in love, bright side hypomania is related to reduced depression and anxiety, and better sleep quality. Int. J. Psychiatry Clin. Pract. 19 24–31. 10.3109/13651501.2014.968588 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Brand S., Luethi M., von Planta A., Hatzinger M., Holsboer-Trachsler E. (2007). Romantic love, hypomania, and sleep pattern in adolescents. J. Adoles. Health 41 69–76. 10.1016/j.jadohealth.2007.01.012 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Bribiescas R. G., Ellison P. T., Gray P. B. (2012). Male life history, reproductive effort, and the evolution of the genus homo new directions and perspectives. Curr. Anthropol. 53 S424–S435. 10.1086/667538 [ CrossRef ] [ Google Scholar ]
• Bringle R. G., Winnick T., Rydell R. J. (2013). The prevalence and nature of unrequited love. SAGE Open 3 : 2158244013492160 . 10.1177/2158244013492160 [ CrossRef ] [ Google Scholar ]
• Broad K. D., Curley J. P., Keverne E. B. (2006). Mother-infant bonding and the evolution of mammalian social relationships. Philos. Trans. R. Soc. B Biol. Sci. 361 2199–2214. 10.1098/rstb.2006.1940 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Burton-Chellew M. N., Dunbar R. I. M. (2015). Romance and reproduction are socially costly. Evol. Behav. Sci. 9 229–241. 10.1037/ebs0000046 [ CrossRef ] [ Google Scholar ]
• Buss D. M. (1988). The evolution of human intrasexual competition - tactics of mate attraction. J. Pers. Soc. Psychol. 54 616–628. 10.1037/0022-3514.54.4.616 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Buss D. M. (1989). Sex-differences in human mate preferences - evolutionary hypothesis tested in 37 cultures. Behav. Brain Sci. 12 1–14. 10.1017/s0140525x00023992 [ CrossRef ] [ Google Scholar ]
• Buss D. M. (2000). The Dangerous Passion: Why Jealousy is as Necessary as Love and Sex. New York, NY: The Free Press. [ Google Scholar ]
• Buss D. M. (2006). Strategies of human mating. Psychol. Top. 15 239–260. [ Google Scholar ]
• Buss D. M. (2016). The Evolution of Desire: Strategies of Human Mating (Revised and updated ed.). New York, NY: Basic Books. [ Google Scholar ]
• Buss D. M. (2019). “The evolution of love in humans ,” in The New Psychology of Love , 2nd Edn, eds Sternberg R. J., Sternberg K. (Cambridge: Cambridge University Press; ). [ Google Scholar ]
• Buss D. M., Abbott M., Angleitner A., Asherian A., Biaggio A., Blancovillasenor A., et al. (1990). Internaitonal preferences in selecting mates - a study of 37 cultures. J. Cross Cult. Psychol. 21 5–47. 10.1177/0022022190211001 [ CrossRef ] [ Google Scholar ]
• Buss D. M., Barnes M. (1986). Preferences in mate selection. J. Pers. Soc. Psychol. 50 559–570. 10.1037/0022-3514.50.3.559 [ CrossRef ] [ Google Scholar ]
• Buss D. M., Durkee P. K., Shackelford T. K., Bowdle B. F., Schmitt D. P., Brase G. L., et al. (2020). Human status criteria: sex differences and similaritis across 14 nations. J. Pers. Soc. Psychol. 119 979–998. 10.1037/pspa0000206 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Buss D. M., Haselton M. G., Shackelford T. K., Bleske A. L., Wakefield J. C. (1998). Adaptations, exaptations, and spandrels. Am. Psychol. 53 533–548. 10.1037/0003-066x.53.5.533 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Buss D. M., Schmitt D. P. (1993). Sexual strategies theory - an evolutionary perspective on human mating. Psychol. Rev. 100 204–232. 10.1037/0033-295x.100.2.204 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Buss D. M., Schmitt D. P. (2019). Mate preferences and their behavioral manifestations. Annu. Rev. Psychol. 70 77–110. [ PubMed ] [ Google Scholar ]
• Buss D. M., Shackelford T. K., McKibbin W. F. (2008). The mate retention inventory-short form (MRI-SF). Pers. Indiv. Differ. 44 322–334. 10.1016/j.paid.2007.08.013 [ CrossRef ] [ Google Scholar ]
• Cacioppo S. (2019). “Neuroimaging of love in the twenty-first crentury ,” in The New Psychology of Love , 2nd Edn, eds Sternberg R. J., Sternberg K. (Cambridge: Cambridge University Press; ), 64–83. [ Google Scholar ]
• Cacioppo S., Bianchi-Demicheli F., Frum C., Pfaus J. G., Lewis J. W. (2012a). The common neural bases between sexual desire and love: a multilevel kernel density fMRI analysis. J. Sex. Med. 9 1048–1054. 10.1111/j.1743-6109.2012.02651.x [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Cacioppo S., Bianchi-Demicheli F., Hatfield E., Rapson R. L. (2012b). Social neuroscience of love. Clin. Neuropsychiatry 9 3–13. [ Google Scholar ]
• Calabrò R. S., Cacciola A., Bruschetta D., Milardi D., Quattrini F., Sciarrone F., et al. (2019). Neuroanatomy and function of human sexual behavior: a neglected or unknown issue? Brain Behav. 9 : e01389 . 10.1002/brb3.1389 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Calisi R. M., Saldanha C. J. (2015). Neurohormones, brain, and behavior: a comparative approach to understanding rapid neuroendocrine action. Integr. Comp. Biol. 55 264–267. 10.1093/icb/icv007 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Call V., Sprecher S., Schwartz P. (1995). The incidence and frequency of marital sex in a national sample. J. Marr. Fam. 57 639–652. 10.2307/353919 [ CrossRef ] [ Google Scholar ]
• Cannas Aghedu F., Veneziani C. A., Manari T., Feybesse C., Bisiacchi P. S. (2018). Assessing passionate love: Italian validation of the PLS (reduced version). Sex. Relationsh. Ther. 35 77–88. 10.1080/14681994.2018.1442570 [ CrossRef ] [ Google Scholar ]
• Carter C. S., Perkeybile A. M. (2018). The monogamy paradox: what do love and sex have to do with it? Front. Ecol. Evol. 6 : 202 . 10.3389/fevo.2018.00202 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Chapais B. (2008). Primeval Kinship: How Pair-Bonding Gave Birth to Human Society. Cambridge, MA: Harvard University Press. [ Google Scholar ]
• Chapais B. (2013). Monogamy, strongly bonded groups, and the evolution of human social structure. Evol. Anthropol. Issues News Rev. 22 52–65. 10.1002/evan.21345 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Chappel S. C., Howles C. (1991). REVIEW: reevaluation of the roles of luteinizing hormone and follicle-stimulating hormone in the ovulatory process. Hum. Reprod. 6 1206–1212. 10.1093/oxfordjournals.humrep.a137513 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Conroy-Beam D., Buss D. M. (2016). How are mate preferences linked with actual mate selection? Tests of mate preference integration algorithms using computer simulations and actual mating couples. PLos One 11 : e0156078 . 10.1371/journal.pone.0156078 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Conroy-Beam D., Goetz C. D., Buss D. M. (2015). “Chapter One - Why do humans form long-term mateships? An evolutionary game-theoretic model ,” in Advances in Experimental Social Psychology , eds Olson J. M., Zanna M. P. (Cambridge, MA: Academic Press; ), 1–39. [ Google Scholar ]
• Conroy-Beam D., Goetz C. D., Buss D. M. (2016). What predicts romantic relationship satisfaction and mate retention intensity: mate preference fulfillment or mate value discrepancies? Evol. Hum. Behav. 37 440–448. 10.1016/j.evolhumbehav.2016.04.003 [ CrossRef ] [ Google Scholar ]
• Curley J. P., Keverne E. B. (2005). Genes, brains and mammalian social bonds. Trends Ecol. Evol. 20 561–567. 10.1016/j.tree.2005.05.018 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• D’Acquisto F. (2017). Affective immunology: where emotions and the immune response converge. Dialog. Clin Neurosci 19 9–19. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Darwin C. (1859). On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. London: John Murray. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Darwin C. (2013). The Descent of Man and Selection in Relation to Sex. Cambridge: Cambridge University Press. [ Google Scholar ]
• Dawkins R. (1982). The Extended Phenotype: The Gene as the Unit of Selection. Oxford, UK: Oxford University Press. [ Google Scholar ]
• Dawson L. H., Shih M. C., de Moor C., Shrier L. (2008). Reasons why adolescents and young adults have sex: associations with psychological characteristics and sexual behavior. J. Sex Res. 45 225–232. 10.1080/00224490801987457 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• de Boer A., van Buel E. M., Ter Horst G. J. (2012). Love is more than just a kiss: a neurobiological perspective on love and affection. Neuroscience 201 114–124. 10.1016/j.neuroscience.2011.11.017 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• de Munck V. C., Korotayev A. (1999). Sexual equality and romantic love: a reanalysis of Rosenblatt’s study on the function of romantic love. Cross Cult. Res. 33 265–277. 10.1177/106939719903300303 [ CrossRef ] [ Google Scholar ]
• Dean J., Keshavan M. (2017). The neurobiology of depression: an integrated view. Asian J. Psychiatry 27 101–111. 10.1016/j.ajp.2017.01.025 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Del Giudice M. (2016). The life history model of psychopathology explains the structure of psychiatric disorders and the emergence of the p factor: a simulation study. Clin. Psychol. Sci. 4 299–311. 10.1177/2167702615583628 [ CrossRef ] [ Google Scholar ]
• DePaulo B. M., Morris W. L. (2006). The unrecognized stereotyping and discrimination against singles. Curr. Direct. Psychol. Sci. 15 251–254. 10.1111/j.1467-8721.2006.00446.x [ CrossRef ] [ Google Scholar ]
• Diamond L. M. (2004). Emerging perspectives on distinctions between romantic love and sexual desire. Curr. Direct. Psychol. Sci. 13 116–119. 10.1111/j.0963-7214.2004.00287.x [ CrossRef ] [ Google Scholar ]
• Diamond L. M., Dickenson J. A. (2012). The neuroimaging of love and desire: review and future directions. Clin. Neuropsychiatry J. Treat. Eval. 9 39–46. [ Google Scholar ]
• Dixson A. (2009). Sexual Selection and the Origins of Human Mating Systems. Oxford: Oxford University Press. [ Google Scholar ]
• Dunbar R. I. M. (2012). The Science of Love and Betrayal. London: Faber and Faber. [ Google Scholar ]
• Dundon C. M., Rellini A. H. (2012). Emotional states of love moderate the association between catecholamines and female sexual responses in the laboratory. J. Sex. Med. 9 2617–2630. 10.1111/j.1743-6109.2012.02799.x [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Durdiakova J. B., Celec P., Koborova I., Sedlackova T., Minarik G., Ostatnikova D. (2017). How do we love? Romantic love style in men is related to lower testosterone levels. Physiol. Res. 66 695–703. 10.33549/physiolres.933523 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Durisko Z., Mulsant B. H., McKenzie K., Andrews P. W. (2016). Using evolutionary theory to guide mental health research. Can. J. Psychiatry 61 159–165. 10.1177/0706743716632517 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Dutra S. J., Cunningham W. A., Kober H., Gruber J. (2015). Elevated striatal reactivity across monetary and social rewards in bipolar I disorder. J. Abnorm. Psychol. 124 890–904. 10.1037/abn0000092 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Edward D. A. (2015). The description of mate choice. Behav. Ecol. 26 301–310. 10.1093/beheco/aru142 [ CrossRef ] [ Google Scholar ]
• Emanuele E., Brondino N., Pesent S., Re S., Geroldi D. (2007). Genetic loading on human loving styles. Neuroendocrinol. Lett. 28 815–821. [ PubMed ] [ Google Scholar ]
• Emanuele E., Politi P., Bianchi M., Minoretti P., Bertona M., Geroldi D. (2006). Raised plasma nerve growth factor levels associated with early-stage romantic love. Psychoneuroendocrinology 31 288–294. 10.1016/j.psyneuen.2005.09.002 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Esch T., Stefano G. B. (2005). Love promotes health. Neuroendocrinol. Lett. 26 264–267. [ PubMed ] [ Google Scholar ]
• Feybesse C., Hatfield E. (2019). “Passionate love ,” in The New Psychology of Love , 2nd Edn, eds Sternberg R. J., Sternberg K. (Cambridge: Cambridge University Press; ). [ Google Scholar ]
• Figueredo A. J., Vásquez G., Brumbach B. H., Schneider S. M. (2004). The heritability of life history strategy: the k-factor, covitality, and personality. Soc. Biol. 51 121–143. 10.1080/19485565.2004.9989090 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Fischer E. K., Nowicki J. P., O’Connell L. A. (2019). Evolution of affiliation: patterns of convergence from genomes to behaviour. Philos. Trans. R. Soc. B Biol. Sci. 374 : 20180242 . 10.1098/rstb.2018.0242 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Fisher H. (1995). “The nature and evolution of romantic love ,” in Romantic Passion: A Universal Experience , ed. Jankowiak W. R. (New York, NY: Columbia University Press; ), 23–41. [ Google Scholar ]
• Fisher H. (2000). Lust, attraction, attachment: biology and evolution of the three primary emotion systems for mating, reproduction, and parenting. J. Sex Educ. Ther. 25 96–104. 10.1080/01614576.2000.11074334 [ CrossRef ] [ Google Scholar ]
• Fisher H. (2006). “ The drive to love: the neural mechanism for mate selection ,” in The New Psychology of Love , eds Sternberg R. J., Weis K. (New Haven, CT: Yale Unviersity Press; ), 87–115. [ Google Scholar ]
• Fisher H. (2011). Why Him? Why Her?: How to Find and Keep Lasting Love , 2nd Edn. London: Oneworld. [ Google Scholar ]
• Fisher H. E. (1998). Lust, attraction, and attachment in mammalian reproduction. Hum. Nat. Interdiscipl. Biosoc. Perspect. 9 23–52. 10.1007/s12110-998-1010-5 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Fisher H. E. (2004). Why We Love: The Nature and Chemistry of Romantic Love. New York, NY: St Martin’s Griffin. [ Google Scholar ]
• Fisher H. E. (2016). Anatomy of Love: A natural History of Mating, Marriage, and Why We Stray. New York, NY: W. W. Norton & Company. [ Google Scholar ]
• Fisher H., Aron A., Brown L. L. (2005). Romantic love: an fMRI study of a neural mechanism for mate choice. J. Comp. Neurol. 493 58–62. 10.1002/cne.20772 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Fisher H. E., Aron A., Brown L. L. (2006). Romantic love: a mammalian brain system for mate choice. Philos. Trans. R. Soc. B Biol. Sci. 361 2173–2186. 10.1098/rstb.2006.1938 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Fisher H. E., Aron A., Mashek D., Li H., Brown L. L. (2002). Defining the brain systems of lust, romantic attraction, and attachment. Arch. Sex. Behav. 31 413–419. 10.1023/a:1019888024255 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Fisher H. E., Brown L. L., Aron A., Strong G., Mashek D. (2010). Reward, addiction, and emotion regulation systems associated with rejection in love. J. Neurophysiol. 104 51–60. 10.1152/jn.00784.2009 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Fisher H. E., Xu X. M., Aron A., Brown L. L. (2016). Intense, passionate, romantic love: a natural addiction? How the fields that investigate romance and substance abuse can inform each other. Front. Psychol. 7 : 687 . 10.3389/fpsyg.2016.00687 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Flajnik M. F., Kasahara M. (2010). Origin and evolution of the adaptive immune system: genetic events and selective pressures. Nat. Rev. Genet. 11 47–59. 10.1038/nrg2703 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Fletcher G. J. O., Simpson J. A., Campbell L., Overall N. C. (2015). Pair-bonding, romantic love, and evolution: the curious case of Homo sapiens . Perspect. Psychol. Sci. 10 20–36. 10.1177/1745691614561683 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Fox C. W., Westneat D. F. (2010). “ Adaptation ,” in Evolutionary Behavioural Ecology , eds Westneat D. F., Fox C. W. (New York, NY: Oxford University Press; ), 16–31. [ Google Scholar ]
• Frank R. H. (1988). Passion Within Reason: The Strategic Role of the Emotions. New York, NY: Norton. [ Google Scholar ]
• French J. A., Cavanaugh J., Mustoe A. C., Carp S. B., Womack S. L. (2018). Social monogamy in nonhuman primates: phylogeny, phenotype, and physiology. J. Sex Res. 55 410–434. 10.1080/00224499.2017.1339774 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Garcia C. Y. (1997). Temporal course of basic components of love along the couple relationship. Psicothema 9 1–15. [ Google Scholar ]
• Garrett A., Chang K. (2008). The role of the amygdala in bipolar disorder development. Dev. Psychopathol. 20 1285–1296. 10.1017/s0954579408000618 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Gavrilets S. (2012). Human origins and the transition from promiscuity to pair-bonding. Proc. Natl. Acad. Sci. U.S.A. 109 9923–9928. 10.1073/pnas.1200717109 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Geary D. C., Vigil J., Byrd-Craven J. (2004). Evolution of human mate choice. J. Sex Res. 41 27–42. 10.1080/00224490409552211 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Gleeson B. T., Kushnick G. (2018). Female status, food security, and stature sexual dimorphism: testing mate choice as a mechanism in human self-domestication. Am. J. Phys. Anthropol. 167 458–469. 10.1002/ajpa.23642 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Goetz C. D., Pillsworth E. G., Buss D. M., Conroy-Beam D. (2019). Evolutionary mismatch in mating. Front. Psychol. 10 : 2709 . 10.3389/fpsyg.2019.02709 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Goldenberg R. L., McClure E. M. (2011). Maternal mortality. Am. J. Obstetr. Gynecol. 205 293–295. 10.1016/j.ajog.2011.07.045 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Gottschall J., Nordlund M. (2006). Romantic love: a literary universal? Philos. Liter. 30 450–470. 10.1353/phl.2006.0030 [ CrossRef ] [ Google Scholar ]
• Graham J. M. (2011). Measuring love in romantic relationships: a meta-analysis. J. Soc. Pers. Relationsh. 28 748–771. 10.1177/0265407510389126 [ CrossRef ] [ Google Scholar ]
• Griskevicius V., Tybur J. M., Sundie J. M., Cialdini R. B., Miller G. F., Kenrick D. T. (2007). Blatant benevolence and conspicuous consumption: when romantic motives elicit strategic costly signals. J. Pers. Soc. Psychol. 93 85–102. 10.1037/0022-3514.93.1.85 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Hatfield E., Bensman L., Rapson R. L. (2012). A brief history of social scientists’ attempts to measure passionate love. J. Soc. Pers. Relationsh. 29 143–164. 10.1177/0265407511431055 [ CrossRef ] [ Google Scholar ]
• Hatfield E., Brinton C., Cornelius J. (1989). Passioante love and anxiety in young adolescents. Motiv. Emot. 13 271–289. 10.1007/bf00995539 [ CrossRef ] [ Google Scholar ]
• Hatfield E., Feybesse C., Narine V., Rapson R. L. (2016). “Passionate love: inspired by angels or demons? ,” in The Psychology of Love and Hate in Intimate Relatinships , ed. Aumer K. (New York, NY: Springer; ). [ Google Scholar ]
• Hatfield E., Rapson R. L. (1993). Love, Sex, and Intimacy: Their Psychology, Biology, and History. New York, NY: HarperCollins College Publishers. [ Google Scholar ]
• Hatfield E., Rapson R. L. (2009). “ The neuropsychology of passionate love and sexual desire ,” in Psychology of Social Relationships , eds Cuyler E., Ackhart M. (Hauppauge, NY: Nova Science; ). [ Google Scholar ]
• Hatfield E., Schmitz E., Cornelius J., Rapson R. L. (1988). Passionate love: how early does it begin? J. Psychol. Hum. Sex. 1 35–51. 10.1300/J056v01n01_04 [ CrossRef ] [ Google Scholar ]
• Hatfield E., Sprecher S. (1986). Measuring passionate love in intimate relationships. J. Adolesc. 9 383–410. 10.1016/S0140-1971(86)80043-4 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Hatfield E., Sprecher S. (2011). “The passionate love scale ,” in Handbook of Sexuality-Related Measures: A Compendium , 3rd Edn, eds Fisher T. D., Davis C. M., Yaber W. L., Davis S. L. (Thousand Oaks, CA: Taylor & Francis; ). [ Google Scholar ]
• Hatfield E., Traupmann J. P., O’Brien M. U., Le Y.-C. L. (2008). The endurance of love: passionate and companionate love in newlywed and long-term marriages. Interpers. Int. J. Pers. Relationsh. 2 35–64. 10.5964/ijpr.v2i1.17 [ CrossRef ] [ Google Scholar ]
• Hatfield E., Walster G. W. (1985). A New Look at Love. Lanham, MD: University Press of America. [ Google Scholar ]
• Hazan C., Diamond L. (2000). The place of attachment in human mating. Rev. Gen. Psychol. 4 186–204. 10.1037/1089-2680.4.2.186 [ CrossRef ] [ Google Scholar ]
• Hazan C., Shaver P. (1987). Romantic love conceptualized as an attachment process. J. Pers. Soc. Psychol. 52 511–524. 10.1037/0022-3514.52.3.511 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Hendrick C., Hendrick S. (1986). A theory and method of love. J. Pers. Soc. Psychol. 50 392–402. 10.1037/0022-3514.50.2.392 [ CrossRef ] [ Google Scholar ]
• Hendrick C., Hendrick S. S. (1989). Research on love - does it measure up. J. Pers. Soc. Psychol. 56 784–794. 10.1037/0022-3514.56.5.784 [ CrossRef ] [ Google Scholar ]
• Hendrick C., Hendrick S. S. (1991). Dimensions of love - a sociobiological interpretation. J. Soc. Clin. Psychol. 10 206–230. 10.1521/jscp.1991.10.2.206 [ CrossRef ] [ Google Scholar ]
• Hendrick C., Hendrick S. S. (2019). “ Styles of romantic love ,” in The New Pscyhology of Love , 2nd Edn, eds Sternberg R. J., Sternberg K. (Cambridge: Cambridge University Press; ). [ Google Scholar ]
• Hendrick C., Hendrick S. S., Dicke A. (1998). The love attitudes scale: short form. J. Soc. Pers. Relationsh. 15 147–159. 10.1177/0265407598152001 [ CrossRef ] [ Google Scholar ]
• Hendrick S. S., Hendrick C. (1995). Gender differences and similarities in sex and love. Pers. Relationsh. 2 55–65. 10.1111/j.1475-6811.1995.tb00077.x [ CrossRef ] [ Google Scholar ]
• Henrich J., Heine S. J., Norenzayan A. (2010). The weirdest people in the world? Behav. Brain Sci. 33 61–83. 10.1017/s0140525x0999152x [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Hill C. A., Blakemore J. E. O., Drumm P. (1997). Mutual and unrequited love in adolescence and young adulthood. Pers. Relationsh. 4 15–23. 10.1111/j.1475-6811.1997.tb00127.x [ CrossRef ] [ Google Scholar ]
• Holloway V., Wylie K. (2015). Sex drive and sexual desire. Curr. Opin. Psychiatry 28 424–429. 10.1097/yco.0000000000000199 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• IsHak W. W., Kahloon M., Fakhry H. (2011). Oxytocin role in enhancing well-being: a literature review. J. Affect. Disord. 130 1–9. 10.1016/j.jad.2010.06.001 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Jahangard L., Rahmani A., Haghighi M., Ahmadpanah M., Sadeghi Bahmani D., Soltanian A. R., et al. (2017). “Always look on the bright side of life!” – Higher hypomania scores are associated with higher mental toughness, increased physical activity, and lower symptoms of depression and lower sleep complaints. Front. Psychol. 8 : 2130 . 10.3389/fpsyg.2017.02130 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Jankowiak W. R. (ed.) (1995). Romantic Passion: A Universal Experience?. New York, NY: Columbia University Press. [ Google Scholar ]
• Jankowiak W. R. (ed.) (2008). Intimacies: Love and Sex Across Cultures. New York, NY: Columbia University Press. [ Google Scholar ]
• Jankowiak W. R., Fischer E. F. (1992). A cross-cultural perspective on romantic love. Ethnology 31 149–155. 10.2307/3773618 [ CrossRef ] [ Google Scholar ]
• Jankowiak W. R., Paladino T. (2008). “ Desiring sex, longing for love: a tripartite continuum ,” in Intimacies: Love and Sex Across Cultures , ed. Jankowiak W. R. (New York: Columbia University Press; ), 1–36. [ Google Scholar ]
• Jonsson E. G., Nothen M. M., Grunhage F., Farde L., Nakashima Y., Propping P., et al. (1999). Polymorphisms in the dopamine D2 receptor gene and their relationships to striatal dopamine receptor density of healthy volunteers. Mol. Psychiatry 4 290–296. 10.1038/sj.mp.4000532 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Johnson Z. V., Young L. J. (2015). Neurobiological mechanisms of social attachment and pair bonding. Curr. Opin. Behav. Sci. 3 38–44. 10.1016/j.cobeha.2015.01.009 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Johnstone R. A., Earn D. J. D. (1999). Imperfect female choice and male mating skew on leks of different sizes. Behav. Ecol. Sociobiol. 45 277–281. 10.1007/s002650050562 [ CrossRef ] [ Google Scholar ]
• Jones A. G., Ratterman N. L. (2009). Mate choice and sexual selection: what have we learned since Darwin? Proc. Natl. Acad. Sci. U.S.A. 106 ( Suppl. 1 ), 10001–10008. 10.1073/pnas.0901129106 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Jørgensen T. N., Christensen P. M., Gether U. (2014). Serotonin-induced down-regulation of cell surface serotonin transporter. Neurochem. Int. 73 107–112. 10.1016/j.neuint.2014.01.005 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Kay R. F., Ross C., Williams B. A. (1997). Anthropoid origins. Science 275 797 . 10.1126/science.275.5301.797 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Kenrick D. T. (2006). “A dynamical evolutionary view of love ,” in The New Psychology of Love , eds Sternberg R. J., Weis K. (New Haven, CT: Yale University Press; ). [ Google Scholar ]
• Kenrick D. T., Sadalla E. K., Groth G., Trost M. R. (1990). Evolution, traits, and the stages of human courship - qualifying the parental investment model. J. Pers. 58 97–116. 10.1111/j.1467-6494.1990.tb00909.x [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Klug H. (2018). Why monogamy? A review of potential ultimate drivers. Front. Ecol. Evol. 6 : 30 . 10.3389/fevo.2018.00030 [ CrossRef ] [ Google Scholar ]
• Koehn M. A., Jonason P. K. (2018). “Costs of short-term mating for women ,” in Encyclopedia of Evolutionary Psychological Science , eds Shackelford T. K., Weekes-Shackelford V. A. (Cham: Springer International Publishing; ), 1–6. [ Google Scholar ]
• Koob G. F., Volkow N. D. (2016). Neurobiology of addiction: a neurocircuitry analysis. Lancet Psychiatry 3 760–773. 10.1016/S2215-0366(16)00104-8 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Kushnick G. (2016). “Ecology of pairbond stability ,” in Encyclopedia of Evolutionary Psychological Science , eds Shackelford T., Weekes-Shackelford V. (New York, NY: Springer; ), 1–7. [ Google Scholar ]
• Kushnick G. (2019). The cradle of humankind: evolutionary approaches to technology and parenting. SocArXiv 10.31235/osf.io/k23md [ CrossRef ] [ Google Scholar ]
• Kuula L., Partonen T., Pesonen A. K. (2020). Emotions relating to romantic love-further disruptors of adolescent sleep. Sleep Health 6 159–165. 10.1016/j.sleh.2020.01.006 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Laland K. N., Brown G. R. (2011). Sense and Nonsense: Evolutionary Perspectives on Human Behaviour , 2nd Edn. Oxford: Oxford University Press. [ Google Scholar ]
• Langeslag S. J. E., van der Veen F. M., Fekkes D. (2012). Blood levels of serotonin are differentially affected by romantic love in men and women. J. Psychophysiol. 26 92–98. 10.1027/0269-8803/a000071 [ CrossRef ] [ Google Scholar ]
• Leckman J. F., Mayes L. C. (1999). Preoccupations and behaviors associated with romantic and parental love - Perspectives on the origin of obsessive-compulsive disorder. Child Adoles. Psychiatr. Clin. N. Am. 8 635–665. [ PubMed ] [ Google Scholar ]
• Lee J. (1976). The Colours of Love. Englewood Cliffs, NJ: Prentice-Hall. [ Google Scholar ]
• Li N. P., Bailey J. M., Kenrick D. T., Linsenmeier J. A. W. (2002). The necessities and luxuries of mate preferences: testing the tradeoffs. J. Pers. Soc. Psychol. 82 947–955. 10.1037//0022-3514.82.6.947 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Li N. P., Meltzer A. L. (2015). The validity of sex-differentiated mate preferences: reconciling the seemingly conflicting evidence. Evol. Behav. Sci. 9 89–106. 10.1037/ebs0000036 [ CrossRef ] [ Google Scholar ]
• Li N. P., van Vugt M., Colarelli S. M. (2018). The evolutionary mismatch hypothesis: implications for psychological science. Curr. Direct. Psychol. Sci. 27 38–44. 10.1177/0963721417731378 [ CrossRef ] [ Google Scholar ]
• Li N. P., Yong J. C., Tov W., Sng O., Fletcher G. J. O., Valentine K. A., et al. (2013). Mate preferences do predict attraction and choices in the early stages of mate selection. J. Pers. Soc. Psychol. 105 757–776. 10.1037/a0033777 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Lieberman D., Hatfield E. (2006). “ Passionate love: cross-cultural and evolutionary perspectives ,” in The New Psychology of Love , (New Haven, CT: Yale University Press; ), 274–297. [ Google Scholar ]
• Liu X., Zhang T., He S., Hong B., Peng D., Su H., et al. (2014). Nerve growth factor variations in patients with mood disorders: no changes in eight weeks of clinical treatment. Neuropsychiatr. Dis. Treat. 10 835–840. 10.2147/NDT.S62741 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Loonen A. J. M., Ivanova S. A. (2015). Circuits regulating pleasure and happiness: the evolution of reward-seeking and misery-fleeing behavioral mechanisms in vertebrates. Front. Neurosci. 9 : 394 . 10.3389/fnins.2015.00394 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Loth M. K., Donaldson Z. R. (2021). Oxytocin, dopamine, and opioid interactions underlying pair bonding: highlighting a potential role for microglia. Endocrinol. 162 : bqaa223 . 10.1210/endocr/bqaa223 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Lovejoy C. O. (1981). The origin of man. Science 211 341–350. 10.1126/science.211.4480.341 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Lukas D., Clutton-Brock T. H. (2013). The evolution of social monogamy in mammals. Science 341 : 526 . 10.1126/science.1238677 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Luoto S. (2019a). An updated theoretical framework for human sexual selection: from ecology, genetics, and life history to extended phenotypes. Adapt. Hum. Behav. Physiol. 5 48–102. 10.1007/s40750-018-0103-6 [ CrossRef ] [ Google Scholar ]
• Luoto S. (2019b). Response to commentaries: life history genetics, fluid intelligence, and extended phenotypes. Adapt. Hum. Behav. Physiol. 5 112–115. 10.1007/s40750-019-0109-8 [ CrossRef ] [ Google Scholar ]
• Luoto S. (2020). Did prosociality drive the evolution of homosexuality? Arch. Sex. Behav . 49 2239–2244. 10.1007/s10508-020-01749-0 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Luoto S., Krams I., Rantala M. J. (2019). A life history approach to the female sexual orientation spectrum: evolution, development, causal mechanisms, and health. Arch. Sex. Behav. 48 1273–1308. 10.1007/s10508-018-1261-0 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Luttbeg B. (2002). Assessing the robustness and optimality of alternative decision rules with varying assumptions. Anim. Behav. 63 805–814. 10.1006/anbe.2001.1979 [ CrossRef ] [ Google Scholar ]
• Maletic V., Raison C. (2014). Integrated neurobiology of bipolar disorder. Front. Psychiatry 5 : 98 . 10.3389/fpsyt.2014.00098 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Manji H. K., Quiroz J. A., Payne J. L., Singh J., Lopes B. P., Viegas J. S., et al. (2003). The underlying neurobiology of bipolar disorder. World Psychiatry 2 136–146. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Marazziti D., Akiskal H. S., Rossi A., Cassano G. B. (1999). Alteration of the platelet serotonin transporter in romantic love. Psychol. Med. 29 741–745. 10.1017/s0033291798007946 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Marazziti D., Baroni S., Giannaccini G., Piccinni A., Mucci F., Catena-Dell’Osso M., et al. (2017). Decreased lymphocyte dopamine transporter in romantic lovers. CNS Spectrums 22 290–294. 10.1017/s109285291600050x [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Marazziti D., Canale D. (2004). Hormonal changes when falling in love. Psychoneuroendocrinology 29 931–936. 10.1016/j.psyneuen.2003.08.006 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Marazziti D., Falaschi V., Lombardi A., Mungai F., Dell’osso L. (2015). Stalking: a neurobiological perspective. Riv. Psichiatr. 50 12–18. Retrieved from <Go to ISI>://WOS:000350408600004 [ PubMed ] [ Google Scholar ]
• Marlowe F. W. (2003). A critical period for provisioning by Hadza men: implications for pair bonding. Evol. Hum. Behav. 24 217–229. 10.1016/s1090-5138(03)00014-x [ CrossRef ] [ Google Scholar ]
• Martin E. I., Ressler K. J., Binder E., Nemeroff C. B. (2009). The neurobiology of anxiety disorders: brain imaging, genetics, and psychoneuroendocrinology. Psychiatr. Clin. North Am. 32 549–575. 10.1016/j.psc.2009.05.004 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Marzec M., Łukasik A. (2017). Love styles in the context of life history theory. Polish Psychol. Bull. 48 237–249. 10.1515/ppb-2017-0027 [ CrossRef ] [ Google Scholar ]
• Masuda M. (2003). Meta-analyses of love scales: do various love scales measure the same psychological constructs? Jpn. Psychol. Res. 45 25–37. 10.1111/1468-5884.00030 [ CrossRef ] [ Google Scholar ]
• Mayr E. (1961). Cause and effect in biology - kinds of causes, predictability, and teleology are viewed by a practicing biologist. Science 134 1501–1506. 10.1126/science.134.3489.1501 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• McCarthy M. M. (2020). A new view of sexual differentiation of mammalian brain. J. Comp. Physiol. Neuroethol. Sens. Neural Behav. Physiol. 206 369–378. 10.1007/s00359-019-01376-8 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• McLennan D. A. (2008). The concept of co-option: why evolution often looks miraculous. Evol. Educ. Outreach 1 247–258. 10.1007/s12052-008-0053-8 [ CrossRef ] [ Google Scholar ]
• McQuaid R. J., McInnis O. A., Abizaid A., Anisman H. (2014). Making room for oxytocin in understanding depression. Neurosci. Biobehav. Rev. 45 305–322. 10.1016/j.neubiorev.2014.07.005 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Meltzer A. L., Makhanova A., Hicks L. L., French J. E., McNulty J. K., Bradbury T. N. (2017). Quantifying the sexual afterglow: the lingering benefits of sex and their implications for pair-bonded relationships. Psychol. Sci. 28 587–598. 10.1177/0956797617691361 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Mercado C. P., Kilic F. (2010). Molecular mechanisms of SERT in platelets: regulation of plasma serotonin levels. Mol. Intervent. 10 231–241. 10.1124/mi.10.4.6 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Mercado E., Hibel L. C. (2017). I love you from the bottom of my hypothalamus: the role of stress physiology in romantic pair bond formation and maintenance. Soc. Pers. Psychol. Compass 11 : e12298 . 10.1111/spc3.12298 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Meston C. M., Buss D. M. (2007). Why humans have sex. Arch. Sex. Behav. 36 477–507. 10.1007/s10508-007-9175-2 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Meston C. M., Buss D. M. (2009). Why Women Have Sex. New York, NY: St Martin’s Griffin. [ Google Scholar ]
• Miller G. F., Todd P. M. (1998). Mate choice turns cognitive. Trends Cogn. Sci. 2 190–198. 10.1016/s1364-6613(98)01169-3 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Mohammad-Zadeh L. F., Moses L., Gwaltney-Brant S. M. (2008). Serotonin: a review. J. Vet. Pharmacol. Therapeut. 31 187–199. 10.1111/j.1365-2885.2008.00944.x [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Mooradian A. D., Morley J. E., Korenman S. G. (1987). Biological actions of androgens. Endocr. Rev. 8 1–28. 10.1210/edrv-8-1-1 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Morin P. A. (1993). Reproductive strategies in chimpanzees. Am. J. Phys. Anthropol. 36 179–212. 10.1002/ajpa.1330360610 [ CrossRef ] [ Google Scholar ]
• Morris W. N. (2003). “The mood system ,” in Well-Being: Foundations of Hedonic Psychology , eds Kahneman D., Diener E., Schwarz N. (New York, NY: Russell Sage Foundation; ), 169–189. [ Google Scholar ]
• Motta-Mena N. V., Puts D. A. (2017). Endocrinology of human female sexuality, mating, and reproductive behavior. Hormon. Behav. 91 19–35. 10.1016/j.yhbeh.2016.11.012 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Murray D. R., Haselton M. G., Fales M., Cole S. W. (2019). Falling in love is associated with immune system gene regulation. Psychoneuroendocrinology 100 120–126. 10.1016/j.psyneuen.2018.09.043 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Nesse R. (2019). Good Reasons for Bad Feelings: Insights Form the Frontier of Evolutionary Psychiatry. Great Britain, UK: Allen Lane. [ Google Scholar ]
• Nesse R. M. (2013). Tinbergen’s four questions, organized: a response to Bateson and Laland. Trends Ecol. Evol. 28 681–682. 10.1016/j.tree.2013.10.008 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Nettle D., Bateson M. (2012). The evolutionary origins of mood and its disorders. Curr. Biol. 22 R712–R721. 10.1016/j.cub.2012.06.020 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Neumann I. D., Landgraf R. (2012). Balance of brain oxytocin and vasopressin: implications for anxiety, depression, and social behaviors. Trends Neurosci. 35 649–659. 10.1016/j.tins.2012.08.004 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Numan M., Young L. J. (2016). Neural mechanisms of mother-infant bonding and pair bonding: similarities, differences, and broader implications. Hormon. Behav. 77 98–112. 10.1016/j.yhbeh.2015.05.015 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Oesch N., Miklousic I. (2012). The dating mind: evolutionary psychology and the emerging science of human courtship. Evol. Psychol. 10 : 147470491201000511 . 10.1177/147470491201000511 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Olderbak S., Figueredo A. J. (2009). Predicting romantic relationship satisfaction from life history strategy. Pers. Indiv. Differ. 46 604–610. 10.1016/j.paid.2008.12.019 [ CrossRef ] [ Google Scholar ]
• O’Leary K. D., Acevedo B. P., Aron A., Huddy L., Mashek D. (2011). Is long-term love more than a rare phenomenon? If so, what are its correlates? Soc. Psychol. Pers. Sci. 3 241–249. 10.1177/1948550611417015 [ CrossRef ] [ Google Scholar ]
• Opie C., Atkinson Q. D., Dunbar R. I. M., Shultz S. (2013). Male infanticide leads to social monogamy in primates. Proc. Natl. Acad. Sci. U.S.A. 110 13328–13332. 10.1073/pnas.1307903110 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Ortigue S., Bianchi-Demicheli F., Hamilton A., Grafton S. T. (2007). The neural basis of love as a subliminal prime: an event-related functional magnetic resonance imaging study. J. Cogn. Neurosci. 19 1218–1230. 10.1162/jocn.2007.19.7.1218 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Ortigue S., Bianchi-Demicheli F., Patel N., Frum C., Lewis J. W. (2010). Neuroimaging of love: fMRI meta-analysis evidence toward new perspectives in sexual medicine. J. Sex. Med. 7 3541–3552. 10.1111/j.1743-6109.2010.01999.x [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Ozer E. J., Dolcini M. M., Harper G. W. (2003). Adolescents’ reasons for having sex: gender differences. J. Adolesc. Health 33 317–319. 10.1016/j.jadohealth.2003.06.012 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Pigliucci M., Kaplan J. (2006). “Testing adaptive hypotheses: historical evidence and human adaptations ,” in Making Sense of Evolution: The Conceptual Foundations of Evolutionary Biology , eds Pigliucci M., Kaplan J. (Chicago, IL: University of Chicago Press; ), 150–174. [ Google Scholar ]
• Pines A. M. (2001). The role of gender and culture in romantic attraction. Eur. Psychol. 6 96–102. 10.1027//1016-9040.6.2.96 [ CrossRef ] [ Google Scholar ]
• Pines A. M. (2005). Falling in Love: Why We Choose The Lovers We Choose , 2nd Edn. New York, NY: Routledge. [ Google Scholar ]
• Porges S. W. (1998). Love: an emergent property of the mammalian autonomic nervous system. Psychoneuroendocrinology 23 837–861. [ PubMed ] [ Google Scholar ]
• Price M., Hides L., Cockshaw W., Staneva A. A., Stoyanov S. R. (2016). Young love: romantic concerns and associated mental health issues among adolescent help-seekers. Behav. Sci. 6 : 14 . 10.3390/bs6020009 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Purba J. S., Hoogendijk W. J. G., Hofman M. A., Swaab D. F. (1996). Increased number of vasopressin- and oxytocin-expressing neurons in the paraventricular nucleus of the hypothalamus in depression. Arch. Gen. Psychiatry 53 137–143. [ PubMed ] [ Google Scholar ]
• Quinlan R. J. (2008). Human pair-bonds: evolutionary functions, ecological variation, and adaptive development. Evol. Anthropol. 17 227–238. 10.1002/evan.20191 [ CrossRef ] [ Google Scholar ]
• Rantala M. J., Luoto S., Krama T., Krams I. (2019). Eating disorders: an evolutionary psychoneuroimmunological approach. Front. Psychol. 10 : 2200 . 10.3389/fpsyg.2019.02200 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Rantala M. J., Luoto S., Krams I., Karlsson H. (2018). Depression subtyping based on evolutionary psychiatry: proximate mechanisms and ultimate functions. Brain Behav. Immun. 69 603–617. 10.1016/j.bbi.2017.10.012 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Reeve H. K., Sherman P. W. (1993). Adaptation and the goals of evolutionary research. Q. Rev. Biol. 68 1–32. 10.1086/417909 [ CrossRef ] [ Google Scholar ]
• Reynaud M., Karila L., Blecha L., Benyamina A. (2010). Is love passion an addictive disorder? Am. J. Drug Alcohol Abuse 36 261–267. 10.3109/00952990.2010.495183 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Riela S., Bajoghli H., Xu X. M., Farnia V., Golshani S., Shakeri J. (2017). Falling in love and passionate love in an iranian sample. Interpersona 11 141–155. 10.5964/ijpr.v11i2.272 [ CrossRef ] [ Google Scholar ]
• Riela S., Rodriguez G., Aron A., Xu X. M., Acevedo B. P. (2010). Experiences of falling in love: investigating culture, ethnicity, gender, and speed. J. Soc. Pers. Relationsh. 27 473–493. 10.1177/0265407510363508 [ CrossRef ] [ Google Scholar ]
• Rosenfeld M. J., Thomas R. J., Hausen S. (2019). Disintermediating your friends: how online dating in the United States displaces other ways of meeting. Proc. Natl. Acad. Sci. U.S.A. 116 17753–17758. 10.1073/pnas.1908630116 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Salska I., Frederick D. A., Pawlowski B., Reilly A. H., Laird K. T., Rudd N. A. (2008). Conditional mate preferences: factors influencing preferences for height. Pers. Indiv. Differ. 44 203–215. 10.1016/j.paid.2007.08.008 [ CrossRef ] [ Google Scholar ]
• Satake A. (2018). “Flowering time as a model trait to bridge proximate and evolutionary questions ,” in Mathematical Modelling in Plant Biology , ed. Morris R. (Switzerland: Springer Nature; ), 171–194. [ Google Scholar ]
• Scelza B. A., Prall S. P., Blumenfield T., Crittenden A. N., Gurven M., Kline M., et al. (2020). Patterns of paternal investment predict cross-cultural variation in jealous response. Nat. Hum. Behav. 4 20–26. 10.1038/s41562-019-0654-y [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Schacht R., Kramer K. L. (2019). Are we monogamous? A review of the evolution of pair-bonding in humans and its contemporary variation cross-culturally. Front. Ecol. Evol. 7 : 230 . 10.3389/fevo.2019.00230 [ CrossRef ] [ Google Scholar ]
• Scheele D., Wille A., Kendrick K. M., Stoffel-Wagner B., Becker B., Gunturkun O., et al. (2013). Oxytocin enhances brain reward system responses in men viewing the face of their female partner. Proc. Natl. Acad. Sci. USA 110 20308–20313. 10.1073/pnas.1314190110 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Schmitt D. P. (2006). “Evolutionary and cross-cultural perspectives on love: the influence of gender, personality, and local ecology on emotional investment in romantic relationships ,” in The New Pscyhology of Love , eds Sternberg R. J., Weis K. (New Haven, CT: Yale University Press; ). [ Google Scholar ]
• Schneiderman I., Kanat-Maymon Y., Zagoory-Sharon O., Feldman R. (2014). Mutual influences between partners’ hormones shape conflict dialog and relationship duration at the initiation of romantic love. Soc. Neurosci. 9 337–351. 10.1080/17470919.2014.893925 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Schneiderman I., Zagoory-Sharon O., Leckman J. F., Feldman R. (2012). Oxytocin during the initial stages of romantic attachment: relations to couples’ interactive reciprocity. Psychoneuroendocrinology 37 1277–1285. 10.1016/j.psyneuen.2011.12.021 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Seymour R. M., Sozou P. D. (2009). Duration of courtship effort as a costly signal. J. Theoret. Biol. 256 1–13. 10.1016/j.jtbi.2008.09.026 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Shackelford T. K., Buss D. M., Weekes-Shackelford V. A. (2003). Wife killings committed in the context of a lovers triangle. Basic Appl. Soc. Psychol. 25 137–143. 10.1207/s15324834basp2502_4 [ CrossRef ] [ Google Scholar ]
• Sheets V. L. (2013). Passion for life: self-expansion and passionate love across the life span. J. Soc. Pers. Relationsh. 31 958–974. 10.1177/0265407513515618 [ CrossRef ] [ Google Scholar ]
• Shiah I. S., Yatham L. N. (2000). Serotonin in mania and in the mechanism of action of mood stabilizers: a review of clinical studies. Bipolar Disord. 2 77–92. 10.1034/j.1399-5618.2000.020201.x [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Shizuka D., Hudson E. J. (2020). To accept or reject heterospecific mates: behavioural decisions underlying premating isolation. Philos. Trans. R. S. B Biol. Sci. 375 : 20190484 . 10.1098/rstb.2019.0484 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Shohayeb B., Diab M., Ahmed M., Ng D. C. H. (2018). Factors that influence adult neurogenesis as potential therapy. Transl. Neurodegen. 7 : 4 . 10.1186/s40035-018-0109-9 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Shultz S., Dunbar R. I. M. (2007). The evolution of the social brain: anthropoid primates contrast with other vertebrates. Proc. R. Soc. B Biol. Sci. 274 2429–2436. 10.1098/rspb.2007.0693 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Silver M., Sabini J., Parrott W. G. (1987). Embarrassment - a dramarugic account. J. Theory Soc. Behav. 17 47–61. 10.1111/j.1468-5914.1987.tb00087.x [ CrossRef ] [ Google Scholar ]
• Song H., Zhang Y., Zuo L., Chen X., Cao G., d’Oleire Uquillas F., et al. (2019). Improving relationships by elevating positive illusion and the underlying psychological and neural mechanisms. Front. Hum. Neurosci. 12 : 526 . 10.3389/fnhum.2018.00526 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Song H. W., Zou Z. L., Kou J., Liu Y., Yang L. Z., Zilverstand A., et al. (2015). Love-related changes in the brain: a resting-state functional magnetic resonance imaging study. Front. Hum. Neurosci. 9 : 13 . 10.3389/fnhum.2015.00071 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Sorokowski P., Sorokowska A., Butovskaya M., Karwowski M., Groyecka A., Wojciszke B., et al. (2017). Love influences reproductive success in humans. Front. Psychol. 8 : 1922 . 10.3389/fpsyg.2017.01922 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Sorokowski P., Sorokowska A., Karwowski M., Groyecka A., Aavik T., Akello G., et al. (2020). Universality of the triangular theory of love: adaptation and psychometric properties of the triangular love scale in 25 countries. J. Sex Res. 58 106–115. 10.1080/00224499.2020.1787318 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Sorokowski P., Zelazniewicz A., Nowak J., Groyecka A., Kaleta M., Lech W., et al. (2019). Romantic love and reproductive hormones in women. International J. Environ. Res. Publ. Health 16 : 4224 . 10.3390/ijerph16214224 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Spitzberg B. H., Cupach W. R. (2003). What mad pursuit? Obsessive relational intrusion and stalking related phenomena. Aggr. Viol. Behav. 8 345–375. 10.1016/s1359-1789(02)00068-x [ CrossRef ] [ Google Scholar ]
• Sprecher S., Aron A., Hatfield E., Cortese A., Potapova E., Levitskaya A. (1994). Love: american style, russian style, and japanese style. Pers. Relationsh. 1 349–369. 10.1111/j.1475-6811.1994.tb00070.x [ CrossRef ] [ Google Scholar ]
• Stephen I. D., Burke D., Sulikowski D. (2017). Tinbergen’s “four questions” provides a formal framework for a more complete understanding of prosocial biases in favour of attractive people. Behav. Brain Sci. 40 38–39. 10.1017/s0140525x16000650 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Sternberg R. J. (1986). A triangular theory of love. Psychol. Rev. 93 119–135. 10.1037/0033-295x.93.2.119 [ CrossRef ] [ Google Scholar ]
• Sternberg R. J. (1997). Construct validation of a triangular love scale. Eur. J. Soc. Psychol. 27 313–335. 10.1002/(sici)1099-0992(199705)27:3<313::Aid-ejsp824<3.3.Co;2-w [ CrossRef ] [ Google Scholar ]
• Sternberg R. J., Sternberg K. (eds) (2019). The New Psychology of Love , 2nd Edn. Cambridge: Cambridge University Press. [ Google Scholar ]
• Stewart-Williams S., Thomas A. G. (2013). The ape that thought it was a peacock: does evolutionary psychology exaggerate human sex differences? Psychol. Inq. 24 137–168. 10.1080/1047840X.2013.804899 [ CrossRef ] [ Google Scholar ]
• Stoessel C., Stiller J., Bleich S., Boensch D., Doerfler A., Garcia M., et al. (2011). Differences and similarities on neuronal activities of people being happily and unhappily in love: a functional magnetic resonance imaging study. Neuropsychobiology 64 52–60. 10.1159/000325076 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Storey A. E., Alloway H., Walsh C. J. (2020). Dads: Progress in understanding the neuroendocrine basis of human fathering behavior. Hormon. Behav. 119 : 104660 . 10.1016/j.yhbeh.2019.104660 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Stulp G., Buunk A. P., Pollet T. V., Nettle D., Verhulst S. (2013). Are human mating preferences with respect to height reflected in actual pairings? PLoS One 8 : e54186 . 10.1371/journal.pone.0054186 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Sugiyama L. S. (2015). “ Physical attractiveness: an adaptationist perspective ,” in The Handbook of Evolutionary Psychology , 2nd Edn, ed. Buss D. M. (Cambridge: Cambridge University Press; ), 412–414. [ Google Scholar ]
• Sullivan R., Perry R., Sloan A., Kleinhaus K., Burtchen N. (2011). Infant bonding and attachment to the caregiver: insights from basic and clinical science. Clin. Perinatol. 38 643–655. 10.1016/j.clp.2011.08.011 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Sumter S. R., Valkenburg P. M., Peter J. (2013). Perceptions of love across the lifespan: differences in passion, intimacy, and commitment. Int. J. Behav. Dev. 37 417–427. 10.1177/0165025413492486 [ CrossRef ] [ Google Scholar ]
• Swami V., Stieger S., Haubner T., Voracek M., Furnham A. (2009). Evaluating the physical attractiveness of oneself and one’s romantic partner individual and relationship correlates of the love-is-blind bias. J. Indiv. Differ. 30 35–43. 10.1027/1614-0001.30.1.35 [ CrossRef ] [ Google Scholar ]
• Takahashi K., Mizuno K., Sasaki A. T., Wada Y., Tanaka M., Ishii A., et al. (2015). Imaging the passionate stage of romantic love by dopamine dynamics. Front. Hum. Neurosci. 9 : 191 . 10.3389/fnhum.2015.00191 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Tarlaci S. (2012). The brain in love: has neuroscience stolen the secret of love? Neuroquantology 10 744–753. 10.14704/nq.2012.10.4.581 [ CrossRef ] [ Google Scholar ]
• Tennov D. (1979). Love and Limerence: The Experience of Being in Love. New York, NY: Stein & Day. [ Google Scholar ]
• Thomas A. G., Jonason P. K., Blackburn J. D., Kennair L. E. O., Lowe R., Malouff J., et al. (2020). Mate preference priorities in the East and West: a cross-cultural test of the mate preference priority model. J. Pers. 88 606–620. 10.1111/jopy.12514 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Tinbergen N. (1963). On aims and methods of Ethology. Zeitschrift Tierpsychol. 20 410–433. 10.1111/j.1439-0310.1963.tb01161.x [ CrossRef ] [ Google Scholar ]
• Todd P. M., Penke L., Fasolo B., Lenton A. P. (2007). Different cognitive processes underlie human mate choices and mate preferences. Proc. Natl. Acad. Sci. U.S.A. 104 15011–15016. 10.1073/pnas.0705290104 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Tomlinson J. M., Aron A., Hatfield E. (2018). “ Romantic love ,” in The Cambridge Handbook of Personal Relationships , eds Vangelisti A. L., Perlman D. (Cambridge: Cambridge University Press; ). [ Google Scholar ]
• Trivers R. L. (1972). “ Parental investment and sexual selection ,” in Sexual Selection and the Descent of Man , ed. Campbell B. (Chicago, IL: Aldine; ), 136–179. [ Google Scholar ]
• Turan T., Uysal C., Asdemir A., Kilic E. (2013). May oxytocin be a trait marker for bipolar disorder? Psychoneuroendocrinology 38 2890–2896. 10.1016/j.psyneuen.2013.07.017 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Ulmer-Yaniv A., Avitsur R., Kanat-Maymon Y., Schneiderman I., Zagoory-Sharon O., Feldman R. (2016). Affiliation, reward, and immune biomarkers coalesce to support social synchrony during periods of bond formation in humans. Brain Behav. Immun. 56 130–139. 10.1016/j.bbi.2016.02.017 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Van Londen L., Goekoop J. G., Zwinderman A. H., Lanser J. B. K., Wiegant V. M., De Wied D. (1998). Neuropsychological performance and plasma cortisol, arginine vasopressin and oxytocin in patients with major depression. Psychol. Med. 28 275–284. 10.1017/s0033291797006284 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Van Overwalle F. (2009). Social cognition and the brain: a meta-analysis. Hum. Brain Mapp. 30 829–858. 10.1002/hbm.20547 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Verhallen A. M., Renken R. J., Marsman J. B. C., ter Horst G. J. (2019). Romantic relationship breakup: an experimental model to study effects of stress on depression (-like) symptoms. PLoS One 14 : e0217320 . 10.1371/journal.pone.0217320 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Wachtmeister C.-A., Enquist M. (2000). The evolution of courtship rituals in monogamous species. Behav. Ecol. 11 405–410. 10.1093/beheco/11.4.405 [ CrossRef ] [ Google Scholar ]
• Walker R. S., Hill K. R., Flinn M. V., Ellsworth R. M. (2011). Evolutionary history of hunter-gatherer marriage practices. PLoS One 6 : e19066 . 10.1371/journal.pone.0019066 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Walster E. H., Walster G. W. (1978). A New Look at Love. Reading, MA: Addison-Wesley. [ Google Scholar ]
• Walter K. V., Conroy-Beam D., Buss D. M., Asao K., Sorokowska A., Sorokowski P., et al. (2020). Sex differences in mate preferences across 45 countries: a large-scale replication. Psychol. Sci. 31 408–423. 10.1177/0956797620904154 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Walum H., Young L. J. (2018). The neural mechanisms and circuitry of the pair bond. Nat. Rev. Neurosci. 19 643–654. 10.1038/s41583-018-0072-6 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Wang A. Y., Nguyen H. T. (1995). Passionate love and anxiety - a cross-generational study. J. Soc. Psychol. 135 459–470. 10.1080/00224545.1995.9712215 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Wang Y. Y., Xu D. D., Feng Y., Chow I. H. I., Ng C. H., Ungvari G. S., et al. (2020). Short versions of the 32-item hypomania checklist: a systematic review. Perspect. Psychiatr. Care 56 102–111. 10.1111/ppc.12388 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Weisman O., Schneiderman I., Zagoory-Sharon O., Feldman R. (2015). Early stage romantic love is associated with reduced daily cortisol production. Adapt. Hum. Behav. Physiol. 1 41–53. 10.1007/s40750-014-0007-z [ CrossRef ] [ Google Scholar ]
• Williams G. C. (2019). Adaptation and Natural Selection: A Critique of Some Current Evolutionary Thought. Princeton, NJ: Princeton University Press. [ Google Scholar ]
• Winterhalder B., Smith E. A. (1992). “ Evolutionary ecology and the social sciences ,” in Evolutionary Ecology and Human Behavior , eds Smith E. A., Winterhalder B. (Hawthorne, NY: Aldine de Gruyter; ), 3–23. [ Google Scholar ]
• Wooderson S. C., Gallagher P., Watson S., Young A. H. (2015). An exploration of testosterone levels in patients with bipolar disorder. Bjpsych. Open 1 136–138. 10.1192/bjpo.bp.115.001008 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Wrosch C., Miller G. E. (2009). Depressive symptoms can be useful: self-regulatory and emotional benefits of dysphoric mood in adolescence. J. Pers. Soc. Psychol. 96 1181–1190. 10.1037/a0015172 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Xu X. M., Aron A., Brown L., Cao G. K., Feng T. Y., Weng X. C. (2011). Reward and motivation systems: a brain mapping study of early-stage intense romantic love in chinese participants. Hum. Brain Mapp. 32 249–257. 10.1002/hbm.21017 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Xu X. M., Brown L., Aron A., Cao G. K., Feng T. Y., Acevedo B., et al. (2012a). Regional brain activity during early-stage intense romantic love predicted relationship outcomes after 40 months: an fMRI assessment. Neurosci. Lett. 526 33–38. 10.1016/j.neulet.2012.08.004 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Xu X. M., Wang J., Aron A., Lei W., Westmaas J. L., Weng X. C. (2012b). Intense passionate love attenuates cigarette cue-reactivity in nicotine-deprived smokers: an fMRI study. PLoS One 7 : e42235 . 10.1371/journal.pone.0042235 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Xu X. M., Weng X. C., Aron A. (2015). “The mesolimbic dopamine pathway and romantic love ,” in Brain Mapping: An Encyclopedic Reference , eds Toga A. W., Mesulam M. M., Kastner S. (Oxford: Elsevier; ). [ Google Scholar ]
• Yancey G., Emerson M. O. (2014). Does height matter? An examination of height preferences in romantic coupling. J. Fam. Issues 37 53–73. 10.1177/0192513X13519256 [ CrossRef ] [ Google Scholar ]
• Young K. A., Gobrogge K. L., Liu Y., Wang Z. X. (2011). The neurobiology of pair bonding: insights from a socially monogamous rodent. Front. Neuroendocrinol. 32 :53–69. 10.1016/j.yfrne.2010.07.006 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Younger J., Aron A., Parke S., Chatterjee N., Mackey S. (2010). Viewing pictures of a romantic partner reduces experimental pain: involvement of neural reward systems. PLoS One 5 : e13309 . 10.1371/journal.pone.0013309 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Zaikman Y., Marks M. J. (2017). Promoting theory-based perspectives in sexual double standard research. Sex Roles 76 407–420. 10.1007/s11199-016-0677-z [ CrossRef ] [ Google Scholar ]
• Zeifman D. M. (2001). An ethological analysis of human infant crying: answering Tinbergen’s four questions. Dev. Psychobiol. 39 265–285. 10.1002/dev.1005 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Zeki S. (2007). The neurobiology of love. FEBS Lett. 581 2575–2579. 10.1016/j.febslet.2007.03.094 [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Zeki S., Romaya J. P. (2010). The brain reaction to viewing faces of opposite- and same-sex romantic partners. PLoS One 5 : e15802 . 10.1371/journal.pone.0015802 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Zietsch B. P., Sidari M. J., Murphy S. C., Sherlock J. M., Lee A. J. (2020). For the good of evolutionary psychology, let’s reunite proximate and ultimate explanations. Evol. Hum. Behav . 42 76–78. 10.1016/j.evolhumbehav.2020.06.009 [ CrossRef ] [ Google Scholar ]
• Zou Z., Song H., Zhang Y., Zhang X. (2016). Romantic love vs. drug addiction may inspire a new treatment for addiction. Front. Psychol. 7 : 1436 . 10.3389/fpsyg.2016.01436 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Zsok F., Haucke M., De Wit C. Y., Barelds D. P. H. (2017). What kind of love is love at first sight? An empirical investigation. Pers. Relationsh. 24 869–885. 10.1111/pere.12218 [ CrossRef ] [ Google Scholar ]

What is love?

Associate professor in Social Psychology / Relationship Science, Deakin University

Disclosure statement

Gery Karantzas receives funding from the Australian Research Council. He is the founder of relationshipscienceonline.com

Deakin University provides funding as a member of The Conversation AU.

View all partners

• Bahasa Indonesia

From songs and poems to novels and movies, romantic love is one of the most enduring subjects for artworks through the ages. But what about the science?

Historical, cultural and even evolutionary evidence suggests love existed during ancient times and across many parts of the world. Romantic love has been found to exist in 147 of 166 cultures looked at in one study.

The complexity of love has much to do with how people experience it differently and how it can change over time.

Read more: Friday essay: finding spaces for love

Like, love, or ‘in love’?

Psychological research over the past 50 years has investigated the differences between liking someone, loving someone and being “in love”.

Liking is described as having positive thoughts and feelings towards someone and finding that person’s company rewarding. We often also experience warmth and closeness towards the people we like. In some instances we choose to be emotionally intimate with these people.

When we love someone we experience the same positive thoughts and experiences as when we like a person. But we also experience a deep sense of care and commitment towards that person.

Being “ in love ” includes all the above but also involves feelings of sexual arousal and attraction. However, research into people’s own views of love suggests that not all love is the same.

Passionate vs companionate love

Romantic love consists of two types: passionate and companionate love. Most romantic relationships, whether they be heterosexual or same sex , involve both these parts.

Passionate love is what people typically consider being “in love”. It includes feelings of passion and an intense longing for someone, to the point they might obsessively think about wanting to be in their arms.

The second part is known as companionate love . It’s not felt as intensely, but it’s complex and connects feelings of emotional intimacy and commitment with a deep attachment toward the romantic partner.

How does love change over time?

Research looking at changes in romantic love over time typically finds that although passionate love starts high, it declines over the course of a relationship.

There are various reasons for this.

As partners learn more about each other and become more confident in the long-term future of the relationship, routines develop. The opportunities to experience novelty and excitement can also decline, as can the frequency of sexual activity . This can cause passionate love to subside.

Although a reduction in passionate love is not experienced by all couples, various studies report approximately 20-40% of couples experience this downturn. Of couples who have been married in excess of ten years, the steepest downturn is most likely to occur over the second decade .

Life events and transitions can also make it challenging to experience passion. People have competing responsibilities which affect their energy and limit the opportunities to foster passion. Parenthood is an example of this.

Read more: Love by design: when science meets sex, lust, attraction and attachment

In contrast, companionate love is typically found to increase over time.

Although research finds most romantic relationships consist of both passionate and companionate love, it’s the absence or reductions in companionate love, moreso than passionate love, that can negatively affect the longevity of a romantic relationship.

But what’s the point of love?

Love is an emotion that keeps people bonded and committed to one another. From an evolutionary psychology perspective, love evolved to keep the parents of children together long enough for them to survive and reach sexual maturity .

Read more: What is this thing called love?

The period of childhood is much longer for humans than other species. As offspring rely on adults for many years to survive and to develop the skills and abilities needed for successful living, love is especially important for humans.

Without love, it’s difficult to see how the human species could have evolved .

A biological foundation too

Not only is there an evolutionary foundation to love, love is rooted in biology. Neurophysiological studies into romantic love show that people who are in the throes of passionate love experience increased activation in brain regions associated with reward and pleasure.

Read more: Love lockdown: the pandemic has put pressure on many relationships, but here's how to tell if yours will survive

In fact, the brain regions activated are the same as those activated by cocaine.

These regions release chemicals such as oxytocin, vasopressin and dopamine, which produce feelings of happiness and euphoria that are also linked to sexual arousal and excitement.

Interestingly, these brain regions are not activated when thinking about non-romantic relationships such as friends. These findings tell us that liking someone is not the same as being in love with someone.

What’s your love style?

Research has found three primary styles of love. First coined by psychologist John Lee , the love styles are eros, ludus and storge. These styles include people’s beliefs and attitudes about love and act as a guide for how to approach romantic relationships.

This style of love refers to erotic love and is focused on physical attraction and engaging in sex, the quick development of strong and passionate feelings for another and intense intimacy.

This style involves being emotionally distant and often involves “game-playing”. It’s not surprising people who endorse this love style are unlikely to commit, feel comfortable ending relationships and often start a new relationship before ending the current one.

Storge is often regarded as a more mature form of love. Priority is given to having a relationship with a person who has similar interests, affection is openly expressed and there is less emphasis on physical attractiveness. People high on storge love are trusting of others and are not needy or dependent on others.

Or is a mixture more your style?

You may see yourself in more than one of these styles.

Evidence suggests some people possess a mixture of the three main love styles; these mixtures were labelled by Lee as mania, pragma and agape.

Read more: Darling, I love you ... from the bottom of my brain

Manic love includes intense feelings for a partner as well as worry about committing to the relationship. Pragmatic love involves making sensible relationship choices in finding a partner who will make a good companion and friend. Agape is a self-sacrificing love that is driven by a sense of duty and selflessness.

Why do you love the way you do?

A person’s love style has little to do with their genetics . Rather, it’s associated with the development of personality and a person’s past relationship experiences.

Some studies have found people who are high on dark traits, such as narcissism, psychopathy and machiavellianism, endorse more of a ludus or pragma love style.

Read more: There are six styles of love. Which one best describes you?

People who have an insecure attachment style , involving a high need for validation and preoccupation with relationship partners, endorse more mania love, while those who are uncomfortable with intimacy and closeness do not endorse eros love.

No matter the differences in the way love is experienced, one thing remains common for all: we as humans are social animals who have a deep fascination for it.

• Relationships

Director, Defence and Security

Director, NIKERI Institute

Communications and Events Officer

Lecturer (Hindi-Urdu)

Opportunities with the new CIEHF

Feb 20, 2023

250-500 Word Example Essays About Love and Romance

Got an Essay assignment about Love and Romance? Let us help you out with these inspiring Examples!

Love, an emotion that has captivated the hearts and minds of poets, authors, and artists throughout history, remains a profound and multi-faceted subject. While the depth and complexity of this emotion can make it a daunting topic to explore in an essay, the right resources can turn this challenge into a rewarding endeavor. For those looking to capture the essence of love and romance in their writing, our essay writer can be a beacon of inspiration and assistance. This tool, powered by Jenni.ai, offers a seamless journey through the essay-writing process, from brainstorming ideas to refining the final draft. 

Whether you're delving into argumentative, persuasive , or reflective essays about love, Jenni.ai ensures clarity, coherence, and a touch of elegance in your prose. It's a trusted companion for students, educators, and seasoned writers alike, simplifying the writing journey every step of the way.

1. The Evolution of Love: A Study of the Changing Nature of Romance throughout History

Introduction.

Love is one of humanity's most complicated and mysterious emotions. People have strived to comprehend and define Love throughout history, resulting in many works of literature, art, and music dedicated to the subject. Despite its universal appeal, the nature of Love has evolved significantly throughout time, reflecting evolving cultural, social, and economic situations. In this essay, we will look at the evolution of Love, from ancient times to the present.

Ancient Love

A. Greek and Roman Love

Love was viewed as a complex and varied feeling in ancient Greece and Rome, comprising characteristics of desire, friendship, and awe. Love was frequently represented as a tremendous force in ancient civilizations, capable of both propelling individuals to high heights of success and bringing them down into the depths of sorrow. This was especially true of romantic Love, which was glorified in epic poems like the Iliad and Odyssey , as well as works of art and literature depicting the hardships and sufferings of star-crossed lovers.

B. Medieval Love

A chivalric code known as courtly Love emerged in medieval Europe. Its core tenants were the importance of Love, honour, and devotion. During this time, romantic Love was typically portrayed as an unrequited emotion, with the lover pining for the affections of a faraway and unreachable beloved. Medieval poets and troubadours mirrored this romanticised picture of Love in their works by singing and writing about the highs and lows of passionate Love.

Modern Love

A. The Renaissance

The idealized picture of Love that had ruled for centuries was called into question by artists and intellectuals during the Renaissance, marking a turning point in the development of romantic relationships. During this time, romantic Love was portrayed as more tactile and visceral. Shakespeare, for instance, reflected the shifting beliefs of his day by exploring the nuanced and often tragic nature of Love in his works.

B. The Enlightenment

The concepts of reason and individuality began to gain root during the Enlightenment, and with that came a shift in how people saw Love. Political marriages and alliances were often formed based on Love, which was now considered a more sensible and practical feeling. Thinkers from the Enlightenment period, including Voltaire and Jean-Jacques Rousseau, shared this perspective on Love as a tool for bettering society and the individual.

C. The Modern Era

Today, the word "love" is most often used to describe a feeling one has when they are in a committed relationship or when one has achieved their own goals. Love has become a consumable good thanks to the spread of consumerism and the worship of the individual. The media and arts reflect this conception of Love by depicting it as a means to one's fulfillment and contentment.

The changing cultural, social, and economic conditions of each historical epoch are reflected in the history of Love. The essence of Love has changed dramatically throughout the years, from its idealised image in ancient Greece and Rome to its depiction as a spiritual tie in mediaeval Europe to its current identification with romantic relationships and personal fulfilment. Despite these changes, Love remains a strong and enduring force in human existence, inspiring numerous works of art, literature, and music and affecting how we live and interact with one another.

2. The Power of Love: Examining the Impact of Love on Our Lives and Relationships

Love is a strong feeling that may dramatically alter our life and the bonds we form with others. love, whether romantic, familial, or platonic, can unite us and improve our lives in countless ways., the benefits of love.

A. Improved Physical Health

Love has been demonstrated to improve physical health by decreasing stress, lowering blood pressure, and increasing immunity. The hormone oxytocin, which is released in response to social bonding and has been demonstrated to reduce physiological responses to stress, is thought to be at play here.

B. Enhanced Mental Health

In addition to its physical benefits, Love has been shown to have a beneficial effect on our mental health, lowering stress and anxiety levels and boosting our general sense of happiness. The protective powers of Love against the negative consequences of stress and other difficulties in life are well accepted.

C. Strengthened Relationships

A stronger tie may be formed between two people via the power of Love. Relationships of all kinds, whether romantic, familial, or platonic, may benefit from the strengthening effects of Love by increasing their levels of closeness, trust, and mutual understanding.

The Challenges of Love

A. Love can be painful

Sometimes Love hurts, as when a relationship ends or when we can't find the one we're looking for. One of life's most trying events is losing someone we care about, which may leave us feeling isolated, discouraged, and empty.

The Power of Love to Overcome Challenges

Despite these difficulties, Love may help us overcome them and grow closer to one another. The strength of Love is that it may help us learn and grow, both as people and as a community, via its many forms, such as forgiveness, compromise, and the willingness to persevere through adversity.

Finally, Love is a strong and transformational force that may profoundly influence our lives and relationships. Love may provide us joy, comfort, and a feeling of purpose, whether between friends, family, or romantic partners. Despite its numerous advantages, Love may also bring with it difficulties such as heartbreak and strife. Nonetheless, never underestimate the power of Love. 

It has the potential to draw people together and form deep, long-lasting bonds. Love has the power to make the world a better place, whether through acts of kindness, selflessness, or simply being there for one another. So, let us embrace Love in all of its manifestations and harness its potential to improve our lives and the lives of those around us.

3. The Science of Love: Understanding the Biology and Psychology Behind Love and Attraction

For millennia, people have been drawn and intrigued by the intricate and intriguing feeling of Love. Despite its enormous global significance, the science of Love is now being thoroughly investigated. This paper will investigate the biology and psychology of Love and attraction, delving into the different elements that impact these powerful emotions and how they form our relationships.

The Biology of Love

A. Hormone Function

Love is a biological process controlled by chemicals such as dopamine, serotonin, and oxytocin. These hormones influence our sensations of attraction, enthusiasm, and enjoyment and boost sentiments of trust and closeness.

B. The Influence of Genetics

Genetics also has an impact on Love and attraction, with some personality qualities and physical characteristics that are considered to be appealing to potential spouses being handed down from generation to generation. This suggests that particular preferences for specific sorts of people are hardwired into our genetics, influencing our romantic and sexual attraction patterns.

The Psychology of Love

A. The Role of Attachment Styles

Our attachment types, which we acquire from our early connections with our caretakers, also affect our Love. These attachment types can significantly influence our later relationships, influencing how we build and keep deep attachments with others.

B. The Impact of Social Norms and Values

Cultural Values

Social conventions and cultural ideas also impact Love and attraction, with societal expectations and values impacting our romantic and sexual impulses. These social conventions and cultural ideas influence everything from who we are attracted to and how we approach and pursue relationships.

The Meeting of Biology and

Love Psychology

The biology and psychology of Love are inextricably linked and interdependent, with one having a complicated and subtle impact on the other. This suggests that, while biology influences our sentiments of attraction and Love, our psychological experiences and beliefs may equally shape these emotions.

To summarise, love science is a complicated and intriguing discipline that encompasses the biology and psychology of this strong and transformational emotion. By investigating the elements that impact Love and attraction, we may gain a deeper understanding of the systems that underpin these feelings and how they shape our lives and relationships. The study of Love is a vital and beneficial effort, whether we seek Love, attempt to preserve Love, or wonder about the science underlying this feeling.

4. The Fine Line Between Love and Obsession: Exploring the Dark Side of Love

Love is a powerful and transformative emotion that can bring immense joy and fulfilment to our lives. But Love can also turn dark and dangerous when it crosses the line into obsession. This essay will examine the fine line between Love and obsession, exploring how Love can become unhealthy and dangerous.

The Characteristics of Obsessive Love

A. Unhealthy Attachment

Obsessive Love is characterized by an unhealthy attachment to another person, with the obsessed person becoming overly dependent on their partner for emotional fulfilment. This can lead to feelings of possessiveness and jealousy, as well as a need for constant attention and validation.

B. Control and Manipulation

Obsessive Love can also involve control and manipulation, with the obsessed person trying to control every aspect of their partner's life and behaviour. This can range from minor acts of manipulation, such as trying to dictate what their partner wears or who they spend time with, to more serious forms of control, such as physical abuse or stalking.

The Dark Side of Love

A. Stalking and Harassment

The dark side of Love can take many forms, with stalking and harassment being among the most extreme and dangerous forms of obsessive behaviour. Stalking and harassment can have serious and long-lasting consequences for the victim, causing fear, stress, and trauma that can impact their mental and physical well-being.

B. Domestic Violence

Domestic violence is another form of the dark side of Love, with physical, sexual, and psychological abuse being used as a means of control and domination. Domestic violence can have devastating consequences for the victim, often leading to serious injury or even death.

The Roots of Obsessive Love

A. Psychological Issues

Obsessive Love can have its roots in psychological issues, including depression, anxiety, and borderline personality disorder. These conditions can lead to feelings of insecurity and low self-esteem, making it difficult for individuals to form healthy relationships.

B. Cultural and Social Factors

Cultural and social factors can also play a role in the development of obsessive Love, with certain societal beliefs and norms promoting possessiveness and control in relationships. This can include gender roles, expectations, and cultural beliefs about Love and relationships.

In conclusion, the fine line between Love and obsession is delicate and dangerous, with Love crossing over into unhealthy and dangerous territory when it becomes obsessive. By understanding the characteristics of obsessive Love and how it can take dark and dangerous forms, we can better protect ourselves and our loved ones from the negative consequences of this powerful emotion.

5. The Concept of Unconditional Love: An Analysis of the Ideal of Selfless Love

All kinds of different things count as Love since it's such a complicated and diverse feeling. Unconditional Love is frequently depicted as altruistic, all-encompassing, and unshakable, making it one of the most romanticized types. In this essay, I'd discuss the idea of unconditional Love, defining it and contrasting it with other types of affection.

An Explanation of Selfless Love

A. Selfless Love

The term "unconditional love" is commonly used to describe a type of Love that puts the other person's needs before its own. In this kind of Love, one person cares for another without any thought of return or compensation.

B. Love that encompasses everything

Many people use the term "all-encompassing" to express how unconditional Love embraces a person regardless of who they are or what they've done in their lives. A love like this doesn't depend on the other person changing or improving in any way; rather, it's an unconditional embrace of the person as they are.

The Ideal of Unconditional Love

A. Love Without Conditions

Unconditional Love is a romantic ideal in which the lover places no restrictions on the object of his affection. Since it involves so much giving of oneself, this kind of Love is typically held up as the pinnacle of romantic relationships.

B. Putting the Feeling into Action

However, since we are all flawed human beings, practising unconditional Love can be challenging in daily life. Although this may be the case, the ideal of unconditional Love is still significant since it motivates us to improve our Love and compassion towards others.

The Advantages of Unconditional Love

A. Stronger Connections

Unconditional Love has the potential to improve our connections with others, leading to deeper and more meaningful bonds. This kind of Love creates a non-judgmental and welcoming attitude towards people, which can assist to lessen conflict and improve understanding.

B. More Joy and Satisfaction

As a result of the more profound relationships it fosters, unconditional Love may also increase a person's sense of well-being and contentment. Finding Love like this may give our life new meaning and make us feel whole.

In conclusion, many of us hold unconditional Love as a relationship goal. Even if it's not always possible, the ideal of unconditional Love is worthwhile since it motivates us to increase our Love and compassion. The concept of unconditional Love may lead us to a more meaningful and happy lifestyle, whether our goal is to better our relationships or to find more pleasure and contentment in general.

6. The Importance of Communication in Love Relationships: A Study of the Role of Communication in Maintaining Love

Love relationships, like all others, benefit greatly from open lines of communication between partners. Connecting with one another on a regular basis, whether it's to chat about the day, express emotions, or problem-solve, is crucial to keeping the Love alive between you. This essay will discuss the significance of communication in romantic relationships, specifically how it helps couples stay together and grow closer over time.

Advantages of good communication

Increased Compatibility and Mutual Understanding

Love partnerships benefit significantly from open lines of communication that facilitate mutual understanding and closeness. Sharing our innermost ideas, emotions, and experiences with our partners via direct and honest communication strengthens our bonds with them.

Reduced Conflict

As we can better address difficulties and find positive solutions to differences when communicating effectively, we experience less conflict in our relationships. Relationships may be stronger and more loving by talking through differences and finding common ground.

The Difficulties in Expressing Your Feelings in a Romantic Relationship

A. Confusing Messages and Confused Intents

Good communication can sometimes be difficult, especially in romantic partnerships, despite its many advantages. Conflict, anger and a lack of trust may all result from poor communication and misunderstandings in relationships.

B. Vulnerability and Emotional Safety

Likewise, it takes courage and trust to open up and talk about your feelings with the person you love. It may be nerve-wracking to communicate our innermost thoughts and feelings with a partner because of the risk of being judged harshly or rejected.

The Importance of Active Listening

What is Active Listening?

Maintaining positive connections with others requires not just good talkers but also good listeners. Paying close attention to the other person as they speak and making an effort to get their viewpoint and requirements is an essential component of active listening.

The Benefits of Active Listening

The ability to listen attentively and process information can have a significant influence on interpersonal bonds. You may show your spouse how much you value their opinion and the commitment you have to the relationship by listening attentively to what they have to say.

Finally, it's important to note that communication is a cornerstone of successful, loving partnerships. Communication is crucial for developing and maintaining healthy relationships , whether it is via problem-solving, venting, or just listening. Your relationship may grow stronger and become more rewarding and loving if you put an emphasis on communicating well with one another.

Final Words

Love is a complicated and varied theme that has inspired numerous works of art, literature, and music. Whether it is the science of Love, the power of Love, or the development of Love, there is a great deal to learn and comprehend about this universal feeling. 

Students now have access to a potent tool that may assist them in writing essays about Love with ease and assurance thanks to Jenni.ai. From giving ideas and recommendations to leading you through the writing process, Jenni.ai is the ideal option for anyone who wants to write about Love and relationships. Why then wait? Sign up for a free trial of Jenni.ai today and explore its numerous writing perks!

Try Jenni for free today

Create your first piece of content with Jenni today and never look back

Essays About Love: 20 Intriguing Ideas for Students

Love can make a fascinating essay topic, but sometimes finding the perfect topic idea is challenging. Here are 20 of the best essays about love.

Writers have often explored the subject of love and what it means throughout history. In his book Essays in Love , Alain de Botton creates an in-depth essay on what love looks like, exploring a fictional couple’s relationship while highlighting many facts about love. This book shows how much there is to say about love as it beautifully merges non-fiction with fiction work.

The New York Times  published an entire column dedicated to essays on modern love, and many prize-winning reporters often contribute to the collection. With so many published works available, the subject of love has much to be explored.

If you are going to write an essay about love and its effects, you will need a winning topic idea. Here are the top 20 topic ideas for essays about love. These topics will give you plenty to think about and explore as you take a stab at the subject that has stumped philosophers, writers, and poets since the dawn of time.

For help with your essays, check out our round-up of the best essay checkers .

1. Outline the Definition of Love

2. describe your favorite love story, 3. what true love looks like, 4. discuss how human beings are hard-wired for love, 5. explore the different types of love, 6. determine the true meaning of love, 7. discuss the power of love, 8. do soul mates exist, 9. determine if all relationships should experience a break-up, 10. does love at first sight exist, 11. explore love between parents and children, 12. discuss the disadvantages of love, 13. ask if love is blind, 14. discuss the chemical changes that love causes, 15. outline the ethics of love, 16. the inevitability of heartbreak, 17. the role of love in a particular genre of literature, 18. is love freeing or oppressing, 19. does love make people do foolish things, 20. explore the theme of love from your favorite book or movie.

Defining love may not be as easy as you think. While it seems simple, love is an abstract concept with multiple potential meanings. Exploring these meanings and then creating your own definition of love can make an engaging essay topic.

To do this, first, consider the various conventional definitions of love. Then, compare and contrast them until you come up with your own definition of love.

One essay about love you could tackle is describing and analyzing a favorite love story. This story could be from a fiction tale or real life. It could even be your love story.

As you analyze and explain the love story, talk about the highs and lows of love. Showcase the hard and great parts of this love story, then end the essay by talking about what real love looks like (outside the flowers and chocolates).

This essay will explore what true love looks like. With this essay idea, you could contrast true love with the romantic love often shown in movies. This contrast would help the reader see how true love looks in real life.

An essay about what true love looks like could allow you to explore this kind of love in many different facets. It would allow you to discuss whether or not someone is, in fact, in true love. You could demonstrate why saying “I love you” is not enough through the essay.

There seems to be something ingrained in human nature to seek love. This fact could make an interesting essay on love and its meaning, allowing you to explore why this might be and how it plays out in human relationships.

Because humans seem to gravitate toward committed relationships, you could argue that we are hard-wired for love. But, again, this is an essay option that has room for growth as you develop your thoughts.

There are many different types of love. For example, while you can have romantic love between a couple, you may also have family love among family members and love between friends. Each of these types of love has a different expression, which could lend itself well to an interesting essay topic.

Writing an essay that compares and contrasts the different types of love would allow you to delve more deeply into the concept of love and what makes up a loving relationship.

What does love mean? This question is not as easy to answer as you might think. However, this essay topic could give you quite a bit of room to develop your ideas about love.

While exploring this essay topic, you may discover that love means different things to different people. For some, love is about how someone makes another person feel. To others, it is about actions performed. By exploring this in an essay, you can attempt to define love for your readers.

What can love make people do? This question could lend itself well to an essay topic. The power of love is quite intense, and it can make people do things they never thought they could or would do.

With this love essay, you could look at historical examples of love, fiction stories about love relationships, or your own life story and what love had the power to do. Then, at the end of your essay, you can determine how powerful love is.

The idea of a soul mate is someone who you are destined to be with and love above all others. This essay topic would allow you to explore whether or not each individual has a soul mate.

If you determine that they do, you could further discuss how you would identify that soul mate. How can you tell when you have found “the one” right for you? Expanding on this idea could create a very interesting and unique essay.

Break-ups seem inevitable, and strong relationships often come back together afterward. Yet are break-ups truly inevitable? Or are they necessary to create a strong bond? This idea could turn into a fascinating essay topic if you look at both sides of the argument.

On the one hand, you could argue that the break-up experience shows you whether or not your relationship can weather difficult times. On the other hand, you could argue that breaking up damages the trust you’re working to build. Regardless of your conclusion, you can build a solid essay off of this topic idea.

Love, at first sight is a common theme in romance stories, but is it possible? Explore this idea in your essay. You will likely find that love, at first sight, is nothing more than infatuation, not genuine love.

Yet you may discover that sometimes, love, at first sight, does happen. So, determine in your essay how you can differentiate between love and infatuation if it happens to you. Then, conclude with your take on love at first sight and if you think it is possible.

The love between a parent and child is much different than the love between a pair of lovers. This type of love is one-sided, with care and self-sacrifice on the parent’s side. However, the child’s love is often unconditional.

Exploring this dynamic, especially when contrasting parental love with romantic love, provides a compelling essay topic. You would have the opportunity to define this type of love and explore what it looks like in day-to-day life.

Most people want to fall in love and enjoy a loving relationship, but does love have a downside? In an essay, you can explore the disadvantages of love and show how even one of life’s greatest gifts is not without its challenges.

This essay would require you to dig deep and find the potential downsides of love. However, if you give it a little thought, you should be able to discuss several. Finally, end the essay by telling the reader whether or not love is worth it despite the many challenges.

Love is blind is a popular phrase that indicates love allows someone not to see another person’s faults. But is love blind, or is it simply a metaphor that indicates the ability to overlook issues when love is at the helm.

If you think more deeply about this quote, you will probably determine that love is not blind. Rather, love for someone can overshadow their character flaws and shortcomings. When love is strong, these things fall by the wayside. Discuss this in your essay, and draw your own conclusion to decide if love is blind.

When someone falls in love, their body feels specific hormonal and chemical changes. These changes make it easier to want to spend time with the person. Yet they can be fascinating to study, and you could ask whether or not love is just chemical reactions or something more.

Grab a science book or two and see if you can explore these physiological changes from love. From the additional sweating to the flushing of the face, you will find quite a few chemical changes that happen when someone is in love.

Love feels like a positive emotion that does not have many ethical concerns, but this is not true. Several ethical questions come from the world of love. Exploring these would make for an interesting and thoughtful essay.

For example, you could discuss if it is ethically acceptable to love an object or even oneself or love other people. You could discuss if it is appropriate to enter into a physical relationship if there is no love present or if love needs to come first. There are many questions to explore with this love essay.

If you choose to love someone, is heartbreak inevitable? This question could create a lengthy essay. However, some would argue that it is because either your object of affection will eventually leave you through a break-up or death.

Yet do these actions have to cause heartbreak, or are they simply part of the process? Again, this question lends itself well to an essay because it has many aspects and opinions to explore.

Literature is full of stories of love. You could choose a genre, like mythology or science fiction, and explore the role of love in that particular genre. With this essay topic, you may find many instances where love is a vital central theme of the work.

Keep in mind that in some genres, like myths, love becomes a driving force in the plot, while in others, like historical fiction, it may simply be a background part of the story. Therefore, the type of literature you choose for this essay would significantly impact the way your essay develops.

Most people want to fall in love, but is love freeing or oppressing? The answer may depend on who your loved ones are. Love should free individuals to authentically be who they are, not tie them into something they are not.

Yet there is a side of love that can be viewed as oppressive, deepening on your viewpoint. For example, you should stay committed to just that individual when you are in a committed relationship with someone else. Is this freeing or oppressive? Gather opinions through research and compare the answers for a compelling essay.

You can easily find stories of people that did foolish things for love. These stories could translate into interesting and engaging essays. You could conclude the answer to whether or not love makes people do foolish things.

Your answer will depend on your research, but chances are you will find that, yes, love makes people foolish at times. Then you could use your essay to discuss whether or not it is still reasonable to think that falling in love is a good thing, although it makes people act foolishly at times.

Most fiction works have love in them in some way. This may not be romantic love, but you will likely find characters who love something or someone.

Use that fact to create an essay. Pick your favorite story, either through film or written works, and explore what love looks like in that work. Discuss the character development, storyline, and themes and show how love is used to create compelling storylines.

If you are interested in learning more, check out our essay writing tips !

Bryan Collins is the owner of Become a Writer Today. He's an author from Ireland who helps writers build authority and earn a living from their creative work. He's also a former Forbes columnist and his work has appeared in publications like Lifehacker and Fast Company.

View all posts

Free Romantic Relationship Essay Examples & Topics

A relationship is a connection between two or more people. Relationships vary in nature and can be positive, negative, platonic, intimate, etc. That is to say, there are numerous types of relationships. Yet, four basic ones are generally recognized in society. You’re likely to be familiar with acquaintanceships, friendships, romantic and family relationships.

Typically, “being in a relationship” refers to a romantic connection between two people. This kind of love is an emotional attachment between individuals, with passion being just one of the prominent features. Romantic relationships involve both spiritual and physical intimacy, commitment, and trust.

In your romantic relationship essay, you can explore this phenomenon using fictional characters from literature or movies. You also have the opportunity to ponder upon the concept of love, its different types and manifestations or analyze your relationships. In this article, our team collected tips that will be useful for writing such a paper. In addition, you will find romantic essay examples and topics on this page.

Romantic Relationship Essay Tips

Your essay about a romantic relationship will depend on the assignment you receive. Besides argumentative and persuasive papers, you may be asked to write reflective or analytical work. Regardless of the essay type, they all have the same basic academic structure. So, here we’ll explain how to start and end this task.

The following aspects will be suitable for argumentative essays about a romantic relationship:

• A catchy hook. Come up with a creative way to grab your readers’ attention from the very first sentence. Ask a question, use a metaphor, or include a quote. You can even provide statistics – use any method to ensure your audience is captivated.
• Some context. The introduction is the place to familiarize your audience with your topic. Provide a general background that will give some context to the rest of your essay. This is also the place to clarify any terms unfamiliar to your readers.
• Thesis statement. Write a sentence that will reflect the main point you are trying to make. A strong thesis statement should guide your readers through your essay. Include the key argument that you will develop in the body of your paper.
• Arguments & supporting evidence. In the main body, develop each key point separately. Here, each paragraph should include a topic sentence, supporting details, and examples. Make sure your arguments are backed up by solid evidence. We recommend you use only trustworthy sources of information (academic articles, official websites with the domain .gov, .edu, etc.).
• Short summary and restatement. In your conclusion, summarize the key points and restate your thesis statement. Do not add any new arguments, facts, or details. The conclusion is the place to review your findings and propose further areas for study.
• A concluding sentence. The key to successful essay writing is a solid and dynamic concluding sentence. It must provide a sense of closure and open space for further study. Spend some time drafting up the perfect last sentence of your essay.

14 Topics about Romantic Relationships

Any successful romantic love essay requires an appropriate topic. Unfortunately, they can be hard to find, especially regarding such a sensitive subject. We created a list of unique ideas to explore and consider in this section. You can also try out our title generator. It will propose even more topics about romantic relationships.

• Factors affecting attractions towards other people during teenage years.
• The role of meaningful conversations in maintaining a healthy relationship between partners.
• The “ideal” boyfriend and girlfriend: fake portrayals of romantic love on social media.
• How can love letters improve the romantic relationship between partners in the digital era?
• Romeo and Juliet as an example of enduring love, commitment, and passion.
• The main principles of interpersonal communication used in conflict resolution.
• Similarities and differences in love expression between adolescents and grownups.
• How may the poor basis for interpersonal relationships affect marriage in the long run?
• Unrequired love among teenagers. What are the threats of experiencing it at a young age?
• What is romantic love? How do you distinguish it from a short-term crush?
• The major stages of relationship development.
• What are some major takeaways about love that we can get from the literature of the Romanic Era?
• How can you be more romantic and maintain passion after long years of married life?
• My ideal love story: the model of romantic relationship I would like to have in my life.

Thank you for your attention! Below you will find romantic essay examples. They will show you how other students handled such an assignment.

57 Best Essay Examples on Romantic Relationship

Why beautiful women prefer unattractive men.

• Words: 1140

Long-Distance and Extended Time Effect on Relationships

• Words: 1991

Arguments: What Is Love?

A woman’s love.

• Words: 1385

Culture Influence on Intimacy and Human Relationships

• Words: 1978

Creating a Healthy Loving Relationship

Students and faculty members’ romantic relations.

• Words: 1457

Love and Its Nature: “Perception of Love in Young Adults”

5 love languages description, gender communication in romantic relationship.

• Words: 1591

The History of Dating and Romantic Relationships

• Words: 1002

Rules of Modern Love and Art of Courtly Love

The influence of pornography on the internet, online relationships are real and positive, “are gen z more pragmatic about love and sex” by klein, love. characteristics of a true feeling, adolescent romantic relationships, “six styles of love” by hendricks and john allan lee, love components in sternberg’s triangular theory, couple relationship: key dimensions.

• Words: 1227

Sexuality and Sexual Happiness Analysis

Interracial romantic relationships, responsibility in romantic relationships, “biochemistry of love” by carter & porges, sociology of the family: love and relationships.

• Words: 1413

Online Dating Platforms, Sex, and Relationships

Love and marriage: “the lady with the pet dog” and “the birthmark”.

• Words: 1009

Dating in Los Angeles: The City of Dreams That Come True

Self-happiness and its impact on romantic relationships, attachment styles and relationships.

• Words: 1416

Interpersonal Attraction Between Two People

• Words: 1059

Mate Preference Based on Personality Traits

The biology of love in knox and schacht’s book and stanislawski’s video, romantic relationship: main aspects.

• Words: 1122

McDonald’s and Romantic Relationships

• Words: 1369

Shteyngart: The Case of Lenny and Eunice

The role of secrecy in erotic romantic love.

• Words: 1547

Matchmaker, Matchmaker, Make Me a Match

• Words: 3969

Dating Online as a Part of Human Life

Ideas of love: western civilizations.

• Words: 4463

What Is The Meaning Of Love?

Long-term intimate relationships.

• Words: 2423

First Date: Sociological Analysis

“sex and the city”: the question of monogamy and polygamy, why people idealize love but do not practice it, why do people search for love.

• Words: 1049

Abusive Intimate Relationships and Turning Points

Attraction and relationships analysis, early dating rituals in filter theory, dual relationships and boundaries in adolescents, infidelity in sexual relationships and marriage.

• Words: 1034

Romantic Relationship Stages and Characteristics

Common conflict areas in marital and couple relationships, creation and breaking of relationships in you’ve got mail and annie hall.

• Words: 1447

Love in a Relationship Without Sex

• Words: 1713

Love, in the Form of Romance, Can Never Give Us What We Want

• Words: 3514

Maintaining and Repairing Relationships

• Words: 1408

REVIEW article

Proximate and ultimate perspectives on romantic love.

A correction has been applied to this article in:

Corrigendum: Proximate and Ultimate Perspectives on Romantic Love

• Read correction

• Human Behavioural Ecology Research Group, School of Archaeology and Anthropology, ANU College of Arts and Social Sciences, The Australian National University, Canberra, ACT, Australia

Romantic love is a phenomenon of immense interest to the general public as well as to scholars in several disciplines. It is known to be present in almost all human societies and has been studied from a number of perspectives. In this integrative review, we bring together what is known about romantic love using Tinbergen’s “four questions” framework originating from evolutionary biology. Under the first question, related to mechanisms, we show that it is caused by social, psychological mate choice, genetic, neural, and endocrine mechanisms. The mechanisms regulating psychopathology, cognitive biases, and animal models provide further insights into the mechanisms that regulate romantic love. Under the second question, related to development, we show that romantic love exists across the human lifespan in both sexes. We summarize what is known about its development and the internal and external factors that influence it. We consider cross-cultural perspectives and raise the issue of evolutionary mismatch. Under the third question, related to function, we discuss the fitness-relevant benefits and costs of romantic love with reference to mate choice, courtship, sex, and pair-bonding. We outline three possible selective pressures and contend that romantic love is a suite of adaptions and by-products. Under the fourth question, related to phylogeny, we summarize theories of romantic love’s evolutionary history and show that romantic love probably evolved in concert with pair-bonds in our recent ancestors. We describe the mammalian antecedents to romantic love and the contribution of genes and culture to the expression of modern romantic love. We advance four potential scenarios for the evolution of romantic love. We conclude by summarizing what Tinbergen’s four questions tell us, highlighting outstanding questions as avenues of potential future research, and suggesting a novel ethologically informed working definition to accommodate the multi-faceted understanding of romantic love advanced in this review.

Introduction

Romantic love is a complex suite of adaptations and by-products that serves a range of functions related to reproduction ( Fletcher et al., 2015 ; Buss, 2019 ). It often occurs early in a romantic relationship but can lead to long-term mating. It is a universal or near-universal ( Jankowiak and Fischer, 1992 ; Gottschall and Nordlund, 2006 ; Jankowiak and Paladino, 2008 ; Fletcher et al., 2015 ; Buss, 2019 ; Sorokowski et al., 2020 ) and is characterized by a range of cognitive, emotional, behavioral, social, genetic, neural, and endocrine activity. It occurs across the lifespan in both sexes. Romantic love serves a variety of functions that vary according to life-stage and duration, including mate choice, courtship, sex, and pair-bonding. Its evolutionary history is probably coupled with the emergence of pair-bonds relatively recently in human evolutionary history.

Romantic love has received attention from scholars in diverse fields, including neurobiology, endocrinology, psychology, and anthropology. Our review aims to synthesize multiple threads of knowledge into a more well-rounded perspective on romantic love. To accomplish this, we do the following: First, we lay out our analytical framework based on Tinbergen’s (1963) “four questions” for explaining a biological phenomenon. Second, using this framework as an organizing tool, we summarize what is known about the social mechanisms, psychological mate choice mechanisms, genetics, neurobiology, endocrinology, development across the lifetime of an individual, fitness-relevant functions, and evolutionary history of romantic love. Finally, we conclude by summarizing what Tinbergen’s four questions tell us, identifying areas for future research, and providing a new ethologically informed working definition of romantic love.

Analytical Framework

Much work has been done to examine romantic love as a biological characteristic. Numerous reviews have described the neurobiology and endocrinology of romantic love (e.g., Fisher, 2004 , 2006 ; Zeki, 2007 ; Hatfield and Rapson, 2009 ; Reynaud et al., 2010 ; Cacioppo et al., 2012b ; de Boer et al., 2012 ; Diamond and Dickenson, 2012 ; Dunbar, 2012 ; Tarlaci, 2012 ; Xu et al., 2015 ; Fisher et al., 2016 ; Zou et al., 2016 ; Tomlinson et al., 2018 ; Walum and Young, 2018 ; Cacioppo, 2019 ). Two meta-analyses ( Ortigue et al., 2010 ; Cacioppo et al., 2012a ) considered fMRI studies of romantic love. There have been some accounts of romantic love or love from an evolutionary perspective (e.g., Hendrick and Hendrick, 1991 ; Fisher, 1995 , 2016 ; Fisher et al., 2006 , 2016 ; Kenrick, 2006 ; Lieberman and Hatfield, 2006 ; Schmitt, 2006 ; Fletcher et al., 2015 ; Sorokowski et al., 2017 ; Buss, 2019 ).

No one, however, has addressed the full spectrum of approaches used in biology to provide a comprehensive account of romantic love. We fill this gap by framing our review of romantic love around Tinbergen’s (1963) “four questions” for explaining biological traits. It was developed in the context of trying to provide a holistic, integrative understanding of animal behavior, and is an extension of earlier explanatory frameworks, including Mayr’s (1961) distinction between proximate and ultimate explanations in biology ( Bateson and Laland, 2013 ). It includes two proximate explanations, mechanistic and ontogenetic, and two ultimate (evolutionary) explanations, functional and phylogenetic. To illustrate the use of this framework, we refer to elements of Zeifman’s (2001) analysis of infant crying as a biological trait using this framework. An outline of our use of this framework is presented in Table 1 .

Table 1. Summary of romantic love using Tinbergen’s (1963) framework.

Proximate explanations focus on the workings of biological and social systems and their components, both on a short-term (mechanistic) and longer-term (ontogenetic) basis ( Tinbergen, 1963 ; Zeifman, 2001 ). Mechanistic explanations attempt to answer questions about how behavior is produced by an organism. It is about the immediate causation of the behavior. A baby’s cry, under this class of explanation, might be viewed as an expression of emotion regulated by the limbic system. In our analysis, we ask: “What are the mechanisms that cause romantic love?” Ontogenetic explanations attempt to answer questions about how the behavior develops over the life course. A baby’s cry, thus, might be viewed as a vocalization that changes in frequency and context over the first year of life, and then across the rest of childhood. In our analysis, we ask: “How does romantic love develop over the lifetime of an individual?”

Ultimate explanations focus on the application of evolutionary logic to understand behavior, both on a short-term (functional) and long-term (phylogenetic) basis ( Tinbergen, 1963 ; Zeifman, 2001 ). Functional explanations attempt to answer questions about the fitness consequences of behavior and how it functions as an adaptation. A baby’s cry, thus, might be viewed as an adaptation that enhances offspring survival by eliciting care or providing information about its state. As the fitness consequences may be negative as well, it might focus on both benefits and costs. For instance, the cry may decrease survival by attracting predators or depleting scarce energy reserves. In our analysis, we ask: “What are the fitness-relevant functions of romantic love?” Phylogenetic explanations attempt to answer questions about the evolutionary history of a behavior and the mechanisms that produce it. A baby’s cry, thus, might be understood from the perspective of whether similar behaviors are present in closely related species. In our analysis, we ask: “What is the evolutionary history of romantic love?”

Tinbergen’s (1963) framework has been a useful tool for organizing research and theory on behavior and other biological traits across all major kingdoms of life, from plants (e.g., Satake, 2018 ) to humans (e.g., Winterhalder and Smith, 1992 ; Zeifman, 2001 ; Stephen et al., 2017 ; Luoto et al., 2019 ). It allows us to build holistic explanations of biological phenomena by examining complementary, but often non-mutually exclusive, categories of explanation ( Bateson and Laland, 2013 ). We believe that this approach to understanding romantic love will clarify the usefulness and interdependence of the various aspects of the biology of romantic love without falling into the pitfalls of posing explanations for the phenomena that are in opposition rather than complementary ( Nesse, 2013 ).

Definitions

There are a number of definitions and descriptions of romantic love. These definitions and descriptions have different names for romantic love, but all are attempting to define the same construct. We present, here, four definitions or descriptions of romantic love that continue to have relevance to contemporary research.

Walster and Walster (1978) were among the first to scientifically define romantic love. They gave it the name “passionate love” and their definition has been revised several times (e.g., Hatfield and Walster, 1985 ; Hatfield and Rapson, 1993 ). A definition of passionate love is:

A state of intense longing for union with another. Passionate love is a complex functional whole including appraisals or appreciations, subjective feelings, expressions, patterned physiological processes, action tendencies, and instrumental behaviors. Reciprocated love (union with the other) is associated with fulfillment and ecstasy; unrequited love (separation) with emptiness, anxiety, or despair ( Hatfield and Rapson, 1993 , p. 5).

Hendrick and Hendrick (1986) propose a description of romantic love in the context of describing six different “love styles” ( Lee, 1976 ). They label it “eros.” It too has undergone some changes. A recent version of the description is:

Strong physical attraction, emotional intensity, a preferred physical appearance, and a sense of inevitability of the relationship define the central core of eros. Eros can “strike” suddenly in a revolution of feeling and thinking ( Hendrick and Hendrick, 2019 , p. 244).

Sternberg (1986) provides a description of romantic love based on three components of love in close relationships: intimacy, passion and commitment. He calls it “romantic love” and describes it as such:

This kind of love derives from a combination of the intimacy and passion components of love. In essence, it is liking with an added element, namely, the arousal brought about by physical attraction and its concomitants. According to this view, then, romantic lovers are not only drawn physically to each other but are also bonded emotionally ( Sternberg, 1986 , p. 124).

A more recent definition of romantic love informed by evolutionary theory has been proposed by Fletcher et al. (2015) . Rather than providing a discrete series of sentences, they propose a working definition of “romantic love” that is explained with reference to some of the psychological research on romantic love and by summarizing five distinct features of romantic love. These features are:

(1) Romantic love is a powerful commitment device, composed of passion, intimacy, and caregiving;

(2) Romantic love is universal and is associated with pair-bonding across cultures;

(3) Romantic love automatically suppresses effort and attention given to alternative partners;

(4) Romantic love has distinct emotional, behavioral, hormonal, and neuropsychological features; and

(5) Successful pair-bonding predicts better health and survival across cultures for both adults and offspring ( Fletcher et al., 2015 , p. 22).

Despite these attempts to define and describe romantic love, no single term or definition has been universally adopted in the literature. The psychological literature often uses the terms “romantic love,” “love,” and “passionate love” (e.g., Sternberg and Sternberg, 2019 ). Seminal work called it “limerence” ( Tennov, 1979 ). The biological literature generally uses the term “romantic love” and has investigated “early stage intense romantic love” (e.g., Xu et al., 2011 ), “long-term intense romantic love” (e.g., Acevedo et al., 2012 ), or being “in love” (e.g., Marazziti and Canale, 2004 ). In this review, what we term “romantic love” encompasses all of these definitions, descriptions, and terms. Romantic love contrasts with “companionate love,” which is felt less intensely, often follows a period of romantic love ( Hatfield and Walster, 1985 ), and merges feelings of intimacy and commitment ( Sternberg, 1986 ).

Psychological Characteristics

Hatfield and Sprecher (1986) theoretically developed the Passionate Love Scale to assess the cognitive, emotional, and behavioral components of romantic love among people who are in a relationship. There are other ways of measuring romantic love ( Hatfield et al., 2012 ), and some, such as Sternberg’s Triangular Love Scale ( Sternberg, 1997 ; Sumter et al., 2013 ) or the Love Attitudes Scale ( Hendrick and Hendrick, 1986 ; Hendrick et al., 1998 ), measure the same constructs ( Masuda, 2003 ; Graham, 2011 ). The Passionate Love Scale is only valid in people who are in a romantic relationship with their loved one. Regardless, the Passionate Love Scale provides a particularly useful account of some of the psychological characteristics of romantic love. It has been used widely in research investigating romantic love in relationships ( Feybesse and Hatfield, 2019 ).

Cognitive components of romantic love include intrusive thinking or preoccupation with the partner, idealization of the other in the relationship, and desire to know the other and to be known. Emotional components include attraction to the other, especially sexual attraction, negative feelings when things go awry, longing for reciprocity, desire for complete union, and physiological arousal. Behavioral components include actions toward determining the other’s feelings, studying the other person, service to the other, and maintaining physical closeness ( Hatfield and Sprecher, 1986 ).

Romantic love shares a number of physiological and psychological characteristics with addiction. “[T]hey focus on their beloved (salience); and they yearn for their beloved (craving). They feel a “rush” of exhilaration when seeing or thinking about him or her (euphoria/intoxication). As their relationship builds, the lover experiences the common signs of drug withdrawal, too, including protest, crying spells, lethargy, anxiety, insomnia, or hypersomnia, loss of appetite or binge eating, irritability and chronic loneliness.” ( Fisher et al., 2016 , p. 2) A number of reviews have highlighted the behavioral and neurobiological similarities between addiction and romantic love (e.g., Reynaud et al., 2010 ; Fisher et al., 2016 ; Zou et al., 2016 ).

There is evidence that romantic love is associated with increased hypomanic symptoms (elevated mood, Brand et al., 2007 ; Bajoghli et al., 2011 , 2013 , 2014 , 2017 ; Brand et al., 2015 ), a change (increase or decrease) in depression symptoms ( Stoessel et al., 2011 ; Bajoghli et al., 2013 , 2014 , 2017 ; Price et al., 2016 ; Verhallen et al., 2019 ; Kuula et al., 2020 ), and increased state anxiety ( Hatfield et al., 1989 ; Wang and Nguyen, 1995 ; Bajoghli et al., 2013 , 2014 , 2017 ; Brand et al., 2015 ; Kuula et al., 2020 ). See Supplementary Table 1 for information about studies investigating hypomania, depression, and anxiety symptoms in people experiencing romantic love. Romantic love is also characterized by cognitive biases which resemble “positive illusions,” which are a tendency to perceive one’s relationship and one’s loved one in a positive light or bias ( Song et al., 2019 ).

Proximate Perspectives

When applied to romantic love, the first of Tinbergen’s (1963) four questions asks: “What are the mechanisms that cause romantic love?” This can be answered with reference to social mechanisms, psychological mate choice mechanisms, genetics, neurobiology, and endocrinology ( Zeifman, 2001 ; Bateson and Laland, 2013 ). Research into the social mechanisms and genetics of romantic love are in their infancy, but there is substantial theory on psychological mate choice mechanisms and ample research has been undertaken into the neural and endocrine activity associated with romantic love. Additional insights can be garnered from the neurobiology and endocrinology of psychopathology, cognitive biases, and animal models.

Social Mechanisms

Some precursors to romantic love (others discussed below) that act strongly as social mechanisms that cause romantic love are reciprocal liking, propinquity, social influence, and the filling of needs (e.g., Aron et al., 1989 ; Pines, 2001 ; Riela et al., 2010 ). Reciprocal liking (mutual attraction) is “being liked by the other, both in general, as well as when it is expressed through self-disclosure” ( Aron et al., 1989 , p. 245). It has been frequently identified as preceding romantic love among participants from the United States and is cross-culturally identified as the strongest preference in mates among both sexes ( Buss et al., 1990 ). “Whether expressed in a warm smile or a prolonged gaze, the message is unmistakable: ‘It’s safe to approach, I like you too. I’ll be nice. You’re not in danger of being rejected”’ ( Hazan and Diamond, 2000 , p. 197). Reciprocal liking may encourage the social approach and courtship activities characteristic and causative of romantic love.

Propinquity is “familiarity, in terms of having spent time together, living near the other, mere exposure to the other, thinking about the other, or anticipating interaction with the other” ( Aron et al., 1989 , p. 245). It has more recently been named “familiarity” (see Riela et al., 2010 ). The extended exposure of an individual to another helps to cause romantic love and specifically facilities the development of romantic love over extended periods of time. Propinquity, in our evolutionary history, served to ensure that “potential mates who are encountered daily at the river’s edge have an advantage over those residing on the other side” ( Hazan and Diamond, 2000 , p. 201). Given that the pool of potential mates in our evolutionary history would have been limited by the size of the groups in which we lived and the fact that most individuals of reproductive age would already have been involved in long-term mating relationships, propinquity is likely to have played a particularly important role in the generation of romantic love. Until recently (to a somewhat lesser extent, today), with the wide-scale take-up of online dating, propinquity played a role in the formation of many long-term pair-bonds, and presumably, romantic love, as is evidenced by a relatively high proportion of people having met their romantic partners in the places where exposure was facilitated, such as school, college, or work ( Rosenfeld et al., 2019 ). Changes in the importance of certain precursors in causing romantic love may be the result of a mismatch between the modern environment and our genotypes that evolved in a very different environment (discussed in detail below; see Li et al., 2018 ).

Social influences are “both general social norms and approval of others in the social network” ( Aron et al., 1989 , p. 245). This may cause people to fall in love with others who are of a similar attractiveness, cultural group, ethnic group, profession, economic class, or who are members of the same social group. Social influences may, directly, impact who we fall in love with by providing approval to a romantic union or, indirectly, by facilitating propinquity. The effect of social influences is demonstrated in the relatively large number of people who met their romantic partner through friends ( Rosenfeld et al., 2019 ). The filling of needs is “having the self’s needs met or meeting the needs of the other (e.g., he makes me happy, she buys me little presents that show she cares), and typically implies characteristics that are highly valued and beneficial in relationship maintenance (e.g., compassion, respect)” ( Riela et al., 2010 , pp. 474–475). The filling of needs may cause romantic love when social interaction facilitates a union where both partners complement each other.

Psychological Mate Choice Mechanisms

Mate choice, in the fields of evolutionary theory, can be defined as “the process that occurs whenever the effects of traits expressed in one sex lead to non-random allocation of reproductive investment with members of the opposite sex” ( Edward, 2015 , p. 301). It is essentially the process of intersexual selection proposed by Darwin (2013) more than 150 years ago ( Darwin, 1859 ) whereby someone has a preference for mating with a particular individual because of that individual’s characteristics. Mate choice, to that extent, involves the identification of a desirable conspecific ( Fisher et al., 2005 ) and sometimes, the focusing of mating energies on that individual. Mate preferences, sexual desire, and attraction all contribute to romantic love. The concepts of “extended phenotypes” and “overall attractiveness” help to explain how these features operate. Romantic love, as discussed below, serves a mate choice function ( Fisher et al., 2005 ) and these mechanisms and constructs contribute to when, and with whom, an individual falls in love.

A large body of research has developed around universal mate preferences (e.g., Buss and Barnes, 1986 ; Buss, 1989 ; Buss et al., 1990 ; Buss and Schmitt, 2019 ; Walter et al., 2020 ). Women, more than men, show a strong preference for resource potential, social status, a slightly older age, ambition and industriousness, dependability and stability, intelligence, compatibility, certain physical indicators, signs of good health, symmetry, masculinity, love, kindness, and commitment ( Buss, 1989 , 2016 ; Walter et al., 2020 ). Men, more than women, have preferences for youth, physical beauty, certain body shapes, chastity, and fidelity ( Buss, 1989 , 2016 ). Both sexes have particularly strong preferences for kindness and intelligence ( Buss et al., 1990 ). A male-taller-than-female norm exists in mate preferences and there is some evidence that women have a preference for taller-than-average height (e.g., Salska et al., 2008 ; Yancey and Emerson, 2014 ). Mutual attraction and reciprocated love are the most important characteristics that both women and men look for in a potential partner ( Buss et al., 1990 ).

Mate choice and attraction may be based on assessments of “extended phenotypes” ( Dawkins, 1982 ; Luoto, 2019a ), which include biotic and abiotic features of the environment that are influenced by an individual’s genes. For example, an extended phenotype would include an individual’s dwelling, car, pets, and social media presence. These can convey information relevant to fitness. Overall mate attractiveness, which is constituted by signs of health and fertility, neurophysiological efficiency, provisioning ability and resources, and capacity for cooperative relationships ( Miller and Todd, 1998 ) may be another heuristic through which attraction and mate choice operate.

Many mate preferences are relatively universal and therefore are likely to have at least some genetic basis (as suggested by, Sugiyama, 2015 ). While mate preferences are linked to actual mate selection ( Li et al., 2013 ; Li and Meltzer, 2015 ; Conroy-Beam and Buss, 2016 ; Buss and Schmitt, 2019 ), strong mate preferences do not always translate into real-world mate choice ( Todd et al., 2007 ; Stulp et al., 2013 ). This is in part because mate preferences function in a tradeoff manner whereby some preferences are given priority over others (see Li et al., 2002 ; Thomas et al., 2020 ). That is, mate choice is a multivariate process that includes the integration and tradeoff of several preferences ( Conroy-Beam et al., 2016 ). Mate preferences are important because they may serve as a means of screening potential mates, while sexual desire and attraction operationalize these preferences, and romantic love crystalizes them.

Sexual desire and attraction may be antecedents to falling in love and there is evidence that physiologically, sexual desire progresses into romantic love within shared neural structures ( Cacioppo et al., 2012a ). However, although both sexual desire and attraction operationalize mate choice, only attraction, and not sexual desire, may be necessary for romantic love to occur (see Leckman and Mayes, 1999 ; Diamond, 2004 ). Intense attraction is characterized by increased energy, focused attention, feelings of exhilaration, intrusive thinking, and a craving for emotional union ( Fisher, 1998 ) although it exists on a spectrum of intensity.

Changes in the expression of at least 61 genes are associated with falling in love in women ( Murray et al., 2019 ) suggesting that these genes may regulate features of romantic love. The DRD2 Taq I A polymorphism, which regulates Dopamine 2 receptor density ( Jonsson et al., 1999 ), is associated with eros ( Emanuele et al., 2007 ). Polymorphisms of genes that regulate vasopressin receptors (AVPR1a rs3), oxytocin receptors (OXTR rs53576), dopamine 4 receptors (DRD4-7R), and dopamine transmission (COMT rs4680) are associated with activity in the ventral tegmental area which, in turn, is associated with eros in newlyweds ( Acevedo et al., 2020 ).

Neurobiology

Neuroimaging studies (see Supplementary Table 2 ) implicate dozens of brain regions in romantic love. We focus, here, on only some of the most frequently replicated findings in an attempt to simplify a description of the neural activity associated with romantic love and explain its psychological characteristics. Romantic love, at least in people who are in a relationship with their loved one, appears to be associated with activity (activation or deactivation compared with a control condition) in four main overlapping systems: reward and motivation, emotions, sexual desire and arousal, and social cognition.

Reward and motivation structures associated with romantic love include those found in the mesolimbic pathway: the ventral tegmental area, nucleus accumbens, amygdala, and medial prefrontal cortex ( Xu et al., 2015 ). Activity in the mesolimbic pathway substantiates the claim that romantic love is a motivational state ( Fisher et al., 2005 ) and helps to explain why romantic love is characterized by psychological features such as longing for reciprocity, desire for complete union, service to the other, maintaining physical closeness, and physiological arousal ( Hatfield and Sprecher, 1986 ).

Emotional centers of the brain associated with romantic love include the amygdala, the anterior cingulate cortex ( Bartels and Zeki, 2000 ; Aron et al., 2005 ; Fisher et al., 2010 ; Younger et al., 2010 ; Zeki and Romaya, 2010 ; Stoessel et al., 2011 ; Acevedo et al., 2012 ; Scheele et al., 2013 ; Song et al., 2015 ), and the insula ( Bartels and Zeki, 2000 ; Aron et al., 2005 ; Ortigue et al., 2007 ; Fisher et al., 2010 ; Younger et al., 2010 ; Zeki and Romaya, 2010 ; Stoessel et al., 2011 ; Acevedo et al., 2012 ; Xu et al., 2012b ; Song et al., 2015 ). Activity in these structures helps to explain romantic love’s emotional features such as negative feelings when things go awry, longing for reciprocity, desire for complete union, and physiological arousal ( Hatfield and Sprecher, 1986 ).

The primary areas associated with both romantic love and sexual desire and arousal include the caudate, insula, putamen, and anterior cingulate cortex ( Diamond and Dickenson, 2012 ). The involvement of these regions helps to explain why people experiencing romantic love feel extremely sexually attracted to their loved one ( Hatfield and Sprecher, 1986 ). The neural similarities and overlapping psychological characteristics of romantic love and sexual desire are well documented (see Hatfield and Rapson, 2009 ; Cacioppo et al., 2012a ; Diamond and Dickenson, 2012 ).

Social cognition centers in the brain repeatedly associated with romantic love include the amygdala, the insula ( Adolphs, 2001 ), and the medial prefrontal cortex ( Van Overwalle, 2009 ). Social cognition plays a role in the social appraisals and cooperation characteristics of romantic love. Activity in these regions helps to explain psychological characteristics such as actions toward determining the other’s feelings, studying the other person, and service to the other ( Hatfield and Sprecher, 1986 ).

In addition to activity in these four systems, romantic love is associated with activity in higher-order cortical brain areas that are involved in attention, memory, mental associations, and self-representation ( Cacioppo et al., 2012b ). Mate choice (a function of romantic love detailed below) has been specifically associated with the mesolimbic pathway and hypothalamus ( Calabrò et al., 2019 ). The mesolimbic pathway, thalamus, hypothalamus, amygdala, septal region, prefrontal cortex, cingulate cortex, and insula have been specifically associated with human sexual behavior ( Calabrò et al., 2019 ), which has implications for the sex function of romantic love (detailed below).

Isolated studies have identified sex differences in the neurobiological activity associated with romantic love. One study ( Bartels and Zeki, 2004 ) found activity in the region ventral to the genu in only women experiencing romantic love. One preliminary study of romantic love (see Fisher et al., 2006 ) found that “[m]en tended to show more activity than women in a region of the right posterior dorsal insula that has been correlated with penile turgidity and male viewing of beautiful faces. Men also showed more activity in regions associated with the integration of visual stimuli. Women tended to show more activity than men in regions associated with attention, memory and emotion” (p. 2181).

Endocrinology

Romantic love is associated with changes in circulating sex hormones, serotonin, dopamine, oxytocin, cortisol, and nerve growth factor systems. Table 2 presents the endocrine factors which are found to be different, compared to controls, in people experiencing romantic love. More information about the controlled studies discussed in this subsection is presented in Supplementary Table 3 . Endocrine factors associated with romantic love have most of their psychological and other effects because of their role as a hormone (e.g., sex hormones, cortisol) or neurotransmitter (e.g., serotonin, dopamine), although many factors operate as both (see Calisi and Saldanha, 2015 ) or as neurohormones.

Table 2. Significant results of controlled endocrine studies investigating romantic love.

Romantic love is associated with changes in the sex hormones testosterone, follicle-stimulating hormone, and luteinizing hormone ( Marazziti and Canale, 2004 ; Durdiakova et al., 2017 ; Sorokowski et al., 2019 ), although the findings have been inconsistent. Testosterone appears to be lower in men experiencing romantic love than controls ( Marazziti and Canale, 2004 ) and higher eros scores are associated with lower levels of testosterone in men ( Durdiakova et al., 2017 ). Lower levels of testosterone in fathers are associated with greater involvement in parenting (see Storey et al., 2020 , for review). The direction of testosterone change in women is unclear (see Marazziti and Canale, 2004 ; Sorokowski et al., 2019 ). Sex hormones are involved in the establishment and maintenance of sexual characteristics, sexual behavior, and reproductive function ( Mooradian et al., 1987 ; Chappel and Howles, 1991 ; Holloway and Wylie, 2015 ). Some sex hormones can influence behavior through their organizing effects resulting from prenatal and postnatal exposure. In the case of romantic love, however, the effects of sex hormones on the features of romantic love are the result of activating effects associated with behaviorally contemporaneous activity. It is possible that sex hormones influence individual differences in the presentation of romantic love through their organizing effect (see Motta-Mena and Puts, 2017 ; Luoto et al., 2019 ; Arnold, 2020 ; McCarthy, 2020 , for descriptions of organizing and activating effects of testosterone, estradiol, and progesterone). Changes in sex hormones could help to explain the increase in sexual desire and arousal associated with romantic love ( Hatfield and Sprecher, 1986 ; Hatfield and Rapson, 2009 ; Diamond and Dickenson, 2012 ).

Romantic love is associated with decreased serotonin transporter density ( Marazziti et al., 1999 ) and changes in plasma serotonin ( Langeslag et al., 2012 ), although inconsistencies have been found in the direction of change according to sex. In one study, men experiencing romantic love displayed lower serotonin levels than controls and women displayed higher serotonin levels than controls ( Langeslag et al., 2012 ). Decreased serotonin transporter density is indicative of elevated extracellular serotonin levels ( Mercado and Kilic, 2010 ; Jørgensen et al., 2014 ). However, decreased levels of serotonin are thought to play a role in depression, mania, and anxiety disorders ( Mohammad-Zadeh et al., 2008 ), including obsessive-compulsive disorder (for a discussion of the relationship between serotonin and OCD, see Baumgarten and Grozdanovic, 1998 ; Rantala et al., 2019 ). One study showed that a sample of mainly women (85% women) experiencing romantic love have similar levels of serotonin transporter density to a sample of both women and men (50% women) with obsessive-compulsive disorder ( Marazziti et al., 1999 ), which could account for the intrusive thinking or preoccupation with the loved one associated with romantic love ( Hatfield and Sprecher, 1986 ).

Lower dopamine transporter density and lower dopamine transporter maximal velocity in lymphocytes have been found in people experiencing romantic love ( Marazziti et al., 2017 ). This is indicative of increased dopamine levels ( Marazziti et al., 2017 ) and is consistent with neuroimaging studies (e.g., Takahashi et al., 2015 ; Acevedo et al., 2020 ) showing activation of dopamine-rich regions of the mesolimbic pathway. One study ( Dundon and Rellini, 2012 ) found no difference in dopamine levels in urine in women experiencing romantic love compared with a control group. Dopamine is involved in reward behavior, sleep, mood, attention, learning, pain processing, movement, emotion, and cognition ( Ayano, 2016 ). Up-regulation of the dopamine system could help to explain the motivational characteristics of romantic love such as longing for reciprocity, desire for complete union, service to the other, and maintaining physical closeness ( Hatfield and Sprecher, 1986 ).

There are no studies that have specifically investigated oxytocin levels in romantic love (at least none that measure romantic love with a validated scale). However, studies ( Schneiderman et al., 2012 , Schneiderman et al., 2014 ; Ulmer-Yaniv et al., 2016 ) have demonstrated that people in the early stages of their romantic relationship have higher levels of plasma oxytocin than controls (singles and new parents). We infer this to mean that reciprocated romantic love is associated with elevated oxytocin levels. Oxytocin plays a role in social affiliation ( IsHak et al., 2011 ) and pair-bonding ( Young et al., 2011 ; Acevedo et al., 2020 ). Oxytocin receptors are prevalent throughout the brain including in the mesolimbic pathway (e.g., Bartels and Zeki, 2000 ). Elevated oxytocin could account for many of the behavioral features of romantic love such as actions toward determining the other’s feelings, studying the other person, service to the other, and maintaining physical closeness ( Hatfield and Sprecher, 1986 ).

Romantic love has been associated with elevated cortisol levels ( Marazziti and Canale, 2004 ), although this has not been replicated ( Sorokowski et al., 2019 ), and one study measuring cortisol in saliva found the opposite ( Weisman et al., 2015 ). Different results could be attributed to different length of time in a relationship between the samples (see Garcia, 1997 ; de Boer et al., 2012 ). Cortisol plays a role in the human stress response by directing glucose and other resources to various areas of the body involved in responding to environmental stressors while simultaneously deactivating other processes (such as digestion and immune regulation, Mercado and Hibel, 2017 ). Elevated cortisol levels may play a role in pair-bond initiation ( Mercado and Hibel, 2017 ) and are indicative of a stressful environment.

Romantic love is associated with higher levels of nerve growth factor, and the intensity of romantic love correlates with levels of nerve growth factor ( Emanuele et al., 2006 ). Nerve growth factor is a neurotrophic implicated in psycho-neuroendocrine plasticity and neurogenesis ( Berry et al., 2012 ; Aloe et al., 2015 ; Shohayeb et al., 2018 ) and could contribute to some of the neural and endocrine changes associated with romantic love.

Insights From the Mechanisms of Psychopathology

Despite “madness” being mentioned in one review of the neurobiology of love ( Zeki, 2007 ) and psychopathology being discussed in studies investigating the endocrinology of romantic love (e.g., Marazziti et al., 1999 , 2017 ), the similarities between romantic love and psychopathology are under-investigated. An understanding of the mechanisms that regulate addiction, mood disorders, and anxiety disorders may help to shed light on the psychological characteristics and mechanisms underlying romantic love and identify areas for future research.

Conceptualizing romantic love as a “natural addiction” (e.g., Fisher et al., 2016 ) not only helps to explain romantic love’s psychological characteristics but provides insight into the mechanisms underlying it (e.g., Zou et al., 2016 ). For example, a neurocircuitry analysis of addiction, drawing on human and animal studies, reveals mechanisms of different “stages” of addiction that have implications for romantic love: binge/intoxication (encompassing drug reward and incentive salience), withdrawal/negative affect, and preoccupation/anticipation ( Koob and Volkow, 2016 ). Each of these stages is associated with particular neurobiological activity and each stage could be represented in romantic love. This may mean that the findings of studies investigating the neurobiology of romantic love (which rely primarily on studies where visual stimuli of a loved one are presented) equates to the binge/intoxication stage of addiction. Findings from studies investigating romantic rejection ( Fisher et al., 2010 ; Stoessel et al., 2011 ; Song et al., 2015 ) may equate to the withdrawal/negative affect stage of addiction. Findings from resting-state fMRI studies ( Song et al., 2015 ; Wang et al., 2020 ) may equate to the preoccupation/anticipation stage of addiction. The result is that current neuroimaging studies may paint a more detailed picture of the neurobiology of romantic love than might initially be assumed.

Mood is an emotional predictor of the short-term prospects of pleasure and pain ( Morris, 2003 ). The adaptive function of mood is, essentially, to integrate information about the environment and state of the individual to fine-tune decisions about behavioral effort ( Nettle and Bateson, 2012 ). Elevated mood can serve to promote goal-oriented behavior and depressed mood can serve to extinguish such behavior ( Wrosch and Miller, 2009 ; Bindl et al., 2012 ; Nesse, 2019 ). Anxious mood is a response to repeated threats ( Nettle and Bateson, 2012 ). Because romantic love can be a tumultuous time characterized by emotional highs, lows, fear, and trepidation, and can involve sustained and repetitive efforts to pursue and retain a mate, it follows that mood circuitry would be closely intertwined with romantic love. Additionally, because romantic love concerns itself with reproduction, which is the highest goal in the realm of evolutionary fitness, it makes sense that mood may impact upon the way romantic love manifests. Understanding the mechanisms that regulate mood can provide insights into psychological characteristics of romantic love and the mechanisms that regulate it. No studies have directly investigated the mechanisms that contribute to changes in mood in people experiencing romantic love. However, insights can be taken from research into the mechanisms of mood and anxiety disorders.

While addiction, hypomania, depression, and anxiety symptoms in people experiencing romantic love may be the normal manifestation of particular mechanisms, symptoms associated with psychopathology may be the manifestations of malfunctioning mechanisms as a result of evolutionary mismatch (see Durisko et al., 2016 ; Li et al., 2018 ). As a result, the mechanisms that cause romantic love and those that cause psychopathology may not be precise models with which to investigate the other. Nonetheless, the mechanisms that cause psychopathology may provide a useful framework with which to base future research into romantic love. Conversely, it may also be that our understanding of the mechanisms that cause romantic love could be a useful framework with which to further investigate psychopathology.

The drug reward and incentive salience features of the binge/intoxication stage of addiction involve changes in dopamine and opioid peptides in the basal ganglia (i.e., striatum, globus pallidus, subthalamic nucleus, and substantia nigra pars reticulata, Koob and Volkow, 2016 ). No research has investigated opioids in romantic love, despite them being involved in monogamy in primates (see French et al., 2018 ) and pair-bonding in rodents ( Loth and Donaldson, 2021 ). The negative emotional states and dysphoric and stress-like responses in the withdrawal/negative affect stage are caused by decreases in the function of dopamine in the mesolimbic pathway and recruitment of brain stress neurotransmitters (i.e., corticotropin-releasing factor, dynorphin), in the extended amygdala ( Koob and Volkow, 2016 ). No studies have investigated corticotropin-releasing factor in romantic love. The craving and deficits in executive function in the preoccupation/anticipation stage of addiction involve the dysregulation of projections from the prefrontal cortex and insula (e.g., glutamate), to the basal ganglia and extended amygdala ( Koob and Volkow, 2016 ). No studies have investigated glutamate in romantic love. There are at least 18 neurochemically defined mini circuits associated with addiction ( Koob and Volkow, 2016 ) that could be the target of research into romantic love. It is likely that romantic love has similar, although not identical, mechanisms to addiction (see Zou et al., 2016 ; Wang et al., 2020 ).

Mania/hypomania (bipolar disorder)

Similar to the brain regions implicated in romantic love, the ventral tegmental area has been associated with mania ( Abler et al., 2008 ), the ventral striatum has been associated with bipolar disorder ( Dutra et al., 2015 ), and the amygdala has been associated with the development of bipolar disorder ( Garrett and Chang, 2008 ). These findings should be interpreted with caution, however, as replicating neuroimaging findings in bipolar disorder has proven difficult (see Maletic and Raison, 2014 ). Research implicates two interrelated prefrontal–limbic networks in elevated mood, which overlap with activity found in romantic love: the automatic/internal emotional regulatory network which includes the ventromedial prefrontal cortex, subgenual anterior cingulate cortex, nucleus accumbens, globus pallidus, and the thalamus, and the volitional/external regulatory network which includes the ventrolateral prefrontal cortex, mid- and dorsal-cingulate cortex, ventromedial striatum, globus pallidus, and thalamus ( Maletic and Raison, 2014 ).

Norepinephrine (theorized to be involved in romantic love, e.g., Fisher, 1998 , 2000 ), serotonin, dopamine, and acetylcholine play a role in bipolar disorder ( Manji et al., 2003 ). One study ( Dundon and Rellini, 2012 ) found no difference in norepinephrine levels in urine in women experiencing romantic love compared with a control group. No studies have investigated acetylcholine in romantic love but romantic love is associated with serotonin ( Marazziti et al., 1999 ; Langeslag et al., 2012 ) and dopamine activity ( Marazziti et al., 2017 ). Similar to the endocrine factors implicated in romantic love ( Emanuele et al., 2006 ; Schneiderman et al., 2012 , 2014 ; Ulmer-Yaniv et al., 2016 ), bipolar patients in a period of mania have also demonstrated higher oxytocin ( Turan et al., 2013 ) and nerve growth factor ( Liu et al., 2014 ) levels and lower levels of serotonin ( Shiah and Yatham, 2000 ). Additionally, there is some evidence that women diagnosed with bipolar disorder present with higher levels of testosterone whereas men present with lower levels of testosterone compared with sex-matched controls ( Wooderson et al., 2015 ). Similar findings have been found in romantic love ( Marazziti and Canale, 2004 ). Dysfunction in the hypothalamic–pituitary–adrenal axis, where cortisol plays a major role, has also been implicated in bipolar disorder ( Maletic and Raison, 2014 ). Cortisol probably plays a role in romantic love ( Marazziti and Canale, 2004 ; Weisman et al., 2015 ).

Neuroimaging studies have implicated changes in functional connectivity in the neural circuits involved in affect regulation in people experiencing depression ( Dean and Keshavan, 2017 ). Increased functional connectivity has been found in networks involving some of the same regions, such as the amygdala, the medial prefrontal cortex, and nucleus accumbens in both people experiencing romantic love and people who recently ended their relationship while in love ( Song et al., 2015 ).

There are a number of endocrine similarities between romantic love and depression. One major pathophysiological theory of depression is that it is caused by an alteration in levels of one or more monoamines, including serotonin, norepinephrine, and dopamine ( Dean and Keshavan, 2017 ). Altered dopamine transmission in depression may be characterized by a down-regulated dopamine system (see Belujon and Grace, 2017 ), which is inferred from numerous human and animal studies, including successful treatment in humans with a dopamine agonist. In romantic love, however, dopamine appears to be up-regulated, especially in areas of the mesolimbic pathway (e.g., Marazziti et al., 2017 ; Bartels and Zeki, 2000 ; Acevedo et al., 2020 ). This could account for some findings that romantic love is associated with a reduction in depression symptoms ( Bajoghli et al., 2013 , 2017 ). However, these need to be reconciled with contrasting findings that romantic love is associated with increased depression symptoms ( Bajoghli et al., 2014 ; Kuula et al., 2020 ) and evidence suggesting that a relationship breakup in people experiencing romantic love is associated with depression symptoms ( Stoessel et al., 2011 ; Price et al., 2016 ; Verhallen et al., 2019 ). The mechanisms that underlie depression might provide a framework for such efforts.

Dysregulation of the HPA axis and associated elevated levels of cortisol is theorized to be one contributor to depression ( Dean and Keshavan, 2017 ). Changes in oxytocin and vasopressin systems (theorized to be involved in romantic love, e.g., Fisher, 1998 , 2000 ; Carter, 2017 ; Walum and Young, 2018 ) are associated with depression (see Purba et al., 1996 ; Van Londen et al., 1998 ; Neumann and Landgraf, 2012 ; McQuaid et al., 2014 ). No studies have investigated vasopressin in people experiencing romantic love. There is also decreased neurogenesis and neuroplasticity in people experiencing depression ( Dean and Keshavan, 2017 ), the opposite of which can be inferred to occur in romantic love because of its substantial neurobiological activity and elevated nerve growth factor (see Berry et al., 2012 ; Aloe et al., 2015 ; Shohayeb et al., 2018 ).

The insular cortex, cingulate cortex, and amygdala are implicated in anxiety and anxiety disorders ( Martin et al., 2009 ). There is also evidence that cortisol, serotonin and norepinephrine are involved ( Martin et al., 2009 ). The substantial overlap between the mechanisms regulating romantic love and those causing anxiety and anxiety disorders provides an opportunity to investigate specific mechanistic effects on the psychological characteristics of romantic love. Assessing state anxiety and these mechanisms concurrently in people experiencing romantic love may be a fruitful area of research.

There is also a need to clarify the role of the serotonin system in romantic love. Similar serotonin transporter density in platelets in people experiencing romantic love and OCD suggests a similar serotonin-related mechanism in both ( Marazziti et al., 1999 ). However, lower serotonin transporter density in platelets is indicative of higher extracellular serotonin levels ( Mercado and Kilic, 2010 ; Jørgensen et al., 2014 ). This is despite lower levels of serotonin being theorized to contribute to anxiety ( Mohammad-Zadeh et al., 2008 ). One study found lower circulating serotonin levels in men experiencing romantic love than controls and higher levels of circulating levels of serotonin in women experiencing romantic love than controls ( Langeslag et al., 2012 ). Insights from the mechanisms regulating anxiety disorders may help to provide a framework with which to further investigate the role of the serotonin system in romantic love and reconcile these findings.

Insights From Cognitive Biases

Positive illusions are cognitive biases about a relationship and loved one that are thought to have positive relationship effects ( Song et al., 2019 ). The research into positive illusions does not use samples of people explicitly experiencing romantic love, and instead uses people in varied stages of a romantic relationship, including those in longer-term pair-bonds. One study ( Swami et al., 2009 ), however, did find a correlation between the “love-is-blind bias” (one type of positive illusion) and eros scores. We also know that cognitive biases resembling positive illusions do exist in romantic love. Both the Passionate Love Scale (e.g., “For me, ____ is the perfect romantic partner,” Hatfield and Sprecher, 1986 , p. 391) and the eros subscale of the Love Attitudes Scale (e.g., “My lover fits my ideal standards of physical beauty/handsomeness,” Hendrick and Hendrick, 1986 , p. 395) include questions about a respondent’s loved one that resemble measures of positive illusions. Understanding the mechanism that regulates positive illusions will provide a model against which the mechanisms regulating the cognitive features of romantic love can be assessed.

A proposed mechanism of positive illusions includes the caudate nucleus, dorsal anterior cingulate cortex, ventral anterior cingulate cortex, orbitofrontal cortex, ventrolateral prefrontal cortical regions, and dorsal medial prefrontal cortex ( Song et al., 2019 ). These regions overlap with the brain regions associated with romantic love. This suggests that the cognitive biases associated with romantic love may be related to, but are distinct from, positive illusions. Targeted neuroimaging studies could ascertain any involvement of the ventrolateral prefrontal cortex and the dorsal medial prefrontal cortex in romantic love. Such research could help to delineate a mechanism that specifically regulates one cognitive aspect of romantic love from those that regulate other psychological aspects of romantic love.

Insights From Mammalian Pair-Bonding Mechanisms

It is not possible to say with any certainty if other animals experience romantic love. Some certainly engage in pair-bonding and exhibit behaviors that are characteristic of romantic love such as obsessive following, affiliative gestures, and mate guarding (see Fisher et al., 2006 ). While some similarities between humans and other animals may be the result of parallel evolution, an understanding of the mechanisms involved in pair-bond formation in other animals can raise questions and guide research into romantic love in humans. Research into monogamous prairie voles, in particular, has identified neurobiological and endocrinological mechanisms that regulate pair-bonding processes. Drawing on this research, a hypothetical neural circuit model of pair-bond formation (pair-bonding) that includes the ventral tegmental area, nucleus accumbens, paraventricular nucleus, amygdala, hippocampus, anterior olfactory nucleus, and medial prefrontal cortex has been proposed ( Walum and Young, 2018 ). Research implicates oxytocin, vasopressin, dopamine, and, potentially, serotonin and cortisol in pair-bonding ( Walum and Young, 2018 ). Most of these neural regions and endocrine factors have been implicated in romantic love in humans. The implications of this research become apparent when the phylogeny of romantic love is presented.

When applied to romantic love, the second of Tinbergen’s (1963) four questions asks: “How does romantic love develop over the lifetime of an individual?” This can be answered with reference to the age of onset of romantic love, its presence throughout the lifespan, and its duration. Questions of ontogeny also encompass issues around the internal and external influences on romantic love ( Tinbergen, 1963 ; Zeifman, 2001 ). We have also chosen to include some consideration of culture in this section because it influences the causes of romantic love. We find that romantic love first develops in childhood, is experienced at all ages in both sexes, usually lasts months or years, but can exist for many years or decades. It is influenced by a range of internal and external factors and is similar across cultures. The modern environment may influence romantic love in ways not present in our evolutionary history.

Romantic Love Over the Lifetime

Romantic love occurs from childhood through adulthood. It first manifests before puberty ( Hatfield et al., 1988 ), with boys and girls as young as four reporting experiences that equate to romantic love. Adolescence is the time in which romantic love first manifests with all of its characteristic features ( Hatfield and Sprecher, 1986 ), including the onset of sexual desire and activity and, potentially, pair-bonding. Romantic love may be more common among adolescents than young adults. In one study ( Hill et al., 1997 ), American university psychology students reported a greater occurrence of mutual and unrequited love experiences when they were 16–20 years old compared to when they were 21–25 years old. However, romantic love exists at all ages of adulthood in both sexes ( Wang and Nguyen, 1995 ).

There are few studies of psychological sex differences in romantic love. Those that exist (e.g., Hatfield and Sprecher, 1986 ; Hendrick and Hendrick, 1995 ; Cannas Aghedu et al., 2018 ) compare the overall intensity of romantic love and find no difference or slightly more intense romantic love in women than men. To our knowledge, no research has specifically investigated sex differences in duration or form of romantic love although it has been shown that some precursors to romantic love may play a greater role in one sex than the other (see Pines, 2001 ; Sprecher et al., 1994 ; Riela et al., 2010 ). As highlighted above, there are small sex differences in the neurobiology of romantic love ( Bartels and Zeki, 2004 ; Fisher et al., 2006 ) and sex differences may exist in the activity of testosterone ( Marazziti and Canale, 2004 ) and serotonin ( Langeslag et al., 2012 ) in people experiencing romantic love, although findings have been inconsistent. These neurobiological and endocrinological differences may, presumably, have differential effects on the presentation of romantic love which have not yet been identified by research.

The psychological features of romantic love are said to normally last between 18 months to 3 years ( Tennov, 1979 ), although studies have found that serotonin transporter density, cortisol levels, testosterone levels, follicle-stimulating hormone levels, and nerve growth factor levels do not differ from controls 12–24 months after initial measurement ( Marazziti et al., 1999 ; Marazziti and Canale, 2004 ; Emanuele et al., 2006 ). Unrequited love has been shown to last an average duration of between 10 and 17 months, depending on the type of unrequited love ( Bringle et al., 2013 ). In that study, unrequited love for someone that an individual pursued lasted the shortest period of time (10.12 months) and romantic love for someone who an individual knows but has not revealed their love to lasted the longest (18.44 months) in a sample of high school and university students from the United States. This contrasts with reciprocated romantic love that lasted even longer (an average of 21.33 months).

The early stages of romantic love characterized by stress may be distinct from a later period characterized by feelings of safety and calm ( Garcia, 1997 ; de Boer et al., 2012 ). The first stage, which is characterized by approximately the first 6 months of a relationship, has been described as “being in love.” It is marked by all the characteristics of romantic love, including, especially, romantic passion and intimacy. The second phase, which has been said to last from approximately 6 months to 4 years, has been referred to as “passional love.” During this time passion is maintained but commitment and intimacy increase. Passional love gives way to companionate love, passion subsides, and commitment and intimacy reach their peaks. While a description of these phases is informative, it is important to recognize that only one study has investigated these phases and they used a sample of predominately university students ( Garcia, 1997 ). Mechanisms research has not adopted these stages and “early stage” romantic love does not specifically refer to the first 6 months of a romantic relationship.

Romantic love exists on a continuum of intensity but can be classified categorically ( Hatfield and Sprecher, 1986 ). The authors of the Passionate Love Scale ( Hatfield and Sprecher, 2011 ) have developed arbitrary cutoffs for differing intensities of romantic love. However the thresholds that define them are not theoretically or empirically derived and are yet to be widely accepted in the literature.

Romantic love can commence abruptly or build up slowly, although the phenomenon of “love at first sight” may actually be strong attraction rather than romantic love, per se ( Sternberg, 1986 ; Zsok et al., 2017 ). In one study of Chinese and American participants, 38% of participants fell in love fast and 35% fell in love slow, with the remaining unknown ( Riela et al., 2010 ). Another study, of Iranians, found that 70% of participants fell in love slowly or very slowly ( Riela et al., 2017 ). Romantic love can end abruptly but often wanes slowly.

Regardless of the normal duration of romantic love, there is a general inverse relationship between the length of time in a relationship and romantic love ( Hatfield et al., 2008 ; Acevedo and Aron, 2009 ). Romantic love normally gives way to failure of a relationship to form, a relationship breakup, or transition to companionate love. However, in some individuals, romantic love can last many years, or even, decades ( O’Leary et al., 2011 ; Acevedo et al., 2012 ; Sheets, 2013 ). In romantic relationships that last, romantic love serves to bond partners together by creating shared understandings, emotions, and habits ( Hatfield and Walster, 1985 ) characteristic of companionate love and long-term pair-bonds. The transition from romantic love to companionate love is gradual and both types of love share many characteristics. In circumstances where romantic love is maintained beyond the initial few years, obsessive thinking about a partner is no longer a feature (e.g., Acevedo and Aron, 2009 ; O’Leary et al., 2011 ).

Internal and External Influences

A number of internal and external influences affect when, with whom, and how we fall in love. The scenario of attachment, separation, and loss in young children ( Bowlby, 1969 , 1973 , 1980 ) is similar to a “desire for union” and may be the groundwork for romantic attachments in later life ( Hatfield et al., 1988 ). To this extent, romantic love, like newborn/infant attachment, is “prewired” into humans as part of their evolutionary heritage ( Hatfield et al., 1989 ). Researchers “focus their investigations on the effects of mother-infant bonding in order to explain variations in the form, duration, and/or frequency of adult passionate relationships” ( Fisher, 1998 , p. 31). For example, a person’s adult attachment style is determined in part by childhood relationships with parents ( Hazan and Shaver, 1987 ) and this may have implications for the experience of romantic love (e.g., Hendrick and Hendrick, 1989 ; Aron et al., 1998 ). Romantic love is positively associated with a secure attachment style and negatively associated with an avoidant attachment style.

Precursors to romantic love include reciprocal liking, appearance, personality, similarity, social influence, filling needs, arousal, readiness, specific cues, isolation, mysteriousness, and propinquity (see Aron et al., 1989 ; Sprecher et al., 1994 ; Riela et al., 2010 ; Riela et al., 2017 ; see also Hazan and Diamond, 2000 ; Fisher, 2011 ). Research also suggests that conscious variables (personality and appearance), situational variables (proximity and arousal), lover variables (lover finds us attractive, lover fills important needs, similarity, and lover is best friend), and unconscious variables (similarity to relationship with parents, similarity of lover to father, similarity of lover to mother, and love at first sight) contribute to with whom we fall in love ( Pines, 2005 ). The majority of precursors are an interplay between internal and external influences.

Some of the most important precursors to romantic love include personality, reciprocal liking, physical appearance, propinquity, specific cues, readiness, and similarity ( Aron et al., 1989 ; Sprecher et al., 1994 ; Riela et al., 2010 , 2017 ). Personality is the “attractiveness of the other’s personality (e.g., intelligent, humorous)” ( Riela et al., 2010 , p. 474). This represents an interplay between internal influences (the preferences of the individual or what they find attractive) and external influences (the personality characteristics of the potential loved one). Reciprocal liking has been defined above and is a mixture of internal and external influences. Physical appearance, too, is an interplay between what an individual finds attractive, either through genetic predisposition or learned experience, and the physical attributes of the potential loved one. Propinquity has been defined and discussed above and is a combination of internal and external influences. Similarity is “having things in common, including attitudes, experiences, interests, and personal factors such as appearance, personality, and family background ( Riela et al., 2010 , p. 474). This is contingent upon both the individual’s characteristics (internal influence) and the potential loved one’s characteristics (external influence).

There are, however, some precursors that are explicitly internal or external influences. Readiness is “being emotionally or physically prepared for seeking a romantic relationship, such as having just broken up with someone and seeking comfort in a new partner” ( Riela et al., 2010 , p. 475). This can be a largely internal influence that can cause romantic love. Specific cues are “particular characteristics of the other (e.g., smile, shape of the eyes), that are relevant to the perceiver in producing strong attractions. This is not the same as attractiveness in general but refers to highly idiosyncratic features of potential love objects that are specifically important to the individual” ( Riela et al., 2010 , p. 475). These are largely external influences that cause romantic love, although they do trigger a biological or psychological response which is internally determined.

Cross-Cultural Perspectives

There have been a number of books (e.g., Jankowiak, 1995 , 2008 ) and studies that shed light on the cross-cultural nature of romantic love. The sum of research indicates that romantic love is probably universal (although the research is yet to prove this unequivocally) with relatively few psychological differences found between cultures (although cultures respond to love in different ways). An ethnographic analysis of 166 cultures from the Standard Cross-Cultural Sample ( Jankowiak and Fischer, 1992 ; Jankowiak and Paladino, 2008 ) found no evidence of romantic love in only 15 cultures, and this was largely due to lack of data. Validated measures of romantic love (i.e., Passionate Love Scale, Love Attitudes Scale, Triangular Love Scale) have been used in at least 50 countries ( Feybesse and Hatfield, 2019 ). The Triangular Theory of Love is robust cross-culturally ( Sorokowski et al., 2020 ). Cross-cultural accounts of the features and the intensity of romantic love are remarkably similar (see Feybesse and Hatfield, 2019 for a review of cross-cultural perspectives on romantic love). Multiple neuroimaging studies have ascertained that the same neural mechanisms associated with romantic love in American samples are associated with romantic love in Chinese samples ( Xu et al., 2011 , 2012b ).

Romantic love may be thought of more positively among Western countries than other countries and Westerners report falling in love more often (see Feybesse and Hatfield, 2019 ). Cultural differences have also been identified in the role of precursors in causing romantic love. A comparison between Japanese, Russian, and American populations found that culture played a role in the self-reported importance of personality, physical appearance, propinquity, similarity, readiness, isolation, mystery, and social standing ( Sprecher et al., 1994 ). Some differences have also been found between Chinese and Americans ( Riela et al., 2010 ) and between Iranians and Americans ( Riela et al., 2017 ) using similar and different methods. In some cultures, romantic love is suppressed and arranged marriages predominate (discussed below).

Evolutionary Mismatch

The evolutionary mismatch hypothesis argues that humans are now living in environments vastly different from those in which they evolved and, as a result, biological mechanisms may not interact with the environment in the manner that they originally evolved to Li et al. (2018) . Adaptations may malfunction. This has implications for the functioning of mechanisms and psychology. Evolutionary mismatch may influence the occurrence, duration, form, and experience of romantic love. As already suggested, evolutionary mismatch may influence the degree to which certain social mechanisms play a role in causing romantic love. This may have flow-on impacts on the frequency with which an individual falls in love or with whom they fall in love. The increased exposure to potential mates may also lead to greater instances of relationship dissolution and new instances of romantic love than would have been the case in our evolutionary history. Evolutionary mismatch may also influence the duration of romantic love. Under evolutionary conditions, romantic love would usually occur in the context of reproduction, pregnancy, and childbirth (see Goetz et al., 2019 ). This may mean that the duration of romantic love may have been shorter in females than is the case in modern developed societies because they are overcome by mother-infant bonding, possibly at the expense of romantic love.

The form and experience of romantic love may also be impacted by evolutionary mismatch. Technology means that lovers are able to maintain regular contact (e.g., by telephone) or be exposed to images of the loved one (e.g., by photographs) in the absence of physical contact. This consistent exposure may be associated with more frequent activation of neural structures associated with romantic love (i.e., reward and motivation structures) and change the intensity or subjective experience of romantic love compared to evolutionary ancestors who may have been completely separated for periods of time.

Ultimate Perspectives

When applied to romantic love, the third of Tinbergen’s (1963) four questions asks: “What are the fitness-relevant functions of romantic love?” Functional explanations address the fitness ramifications (survival and reproduction) of the behavior or trait of interest ( Tinbergen, 1963 ; Zeifman, 2001 ; Bateson and Laland, 2013 ). We are, thus, concerned with both the fitness-relevant benefits and costs of romantic love. We have outlined the benefits and costs of romantic love associated with five functions based on a small literature on the subject (i.e., Fletcher et al., 2015 ; Buss, 2019 ), reproduction-related literature, and our consideration of the subject. Some of the benefits we describe can be considered functions in their own right (e.g., Buss, 2019 ). Table 3 presents a summary of benefits and costs of romantic love according to five distinct yet interrelated functions: mate choice, courtship, sex, pair-bonding, and health. Our approach is to describe each function, present the benefits associated with each function, and present the costs associated with each function. Where relevant, we have included information about related concepts or theories. We contend that while there is a small amount of evidence for the health promoting benefits of romantic love, the evidence is insufficient to say with certainty that health promotion is a function of romantic love. We conclude this section by summarizing some potential selective pressures and describing romantic love as a complex suite of adaptations and by-products.

Table 3. Reproduction- and survival-related benefits and costs associated with each function of romantic love.

Mate Choice

Romantic love serves a mate choice function ( Fisher et al., 2006 ). Both men and women engage in mate choice ( Stewart-Williams and Thomas, 2013 ). Assessing potential mates has important fitness consequences for individuals, as the benefits of finding a suitable mate are often higher than mating haphazardly or with a randomly selected mate ( Geary et al., 2004 ; Andersson and Simmons, 2006 ; Jones and Ratterman, 2009 ; Shizuka and Hudson, 2020 ). On the other hand, mate choice is a costly and error-prone activity and, thus, it may be adaptive to focus one’s attention on a particular mate that has been identified as a preferred partner ( Bowers et al., 2012 ). Romantic love serves this function.

Mate choice evolved in mammals to enable individuals to conserve their mating energy, choose between potential mates, and focus their attention on particular potential mating partners ( Fisher, 2000 ; Fisher et al., 2006 ). The focus of one’s attention on a single potential mate is not without costs (e.g., Klug, 2018 ; Bear and Rand, 2019 ). Imperfect mate choice (e.g., Johnstone and Earn, 1999 ) could result from imperfect information (e.g., Luttbeg, 2002 ) or acceptance or rejection errors. Imperfect information might include the concealment of information that has detrimental effects on fitness. Time to assess an individual is important in mate choice and imperfect mate choice could potentially be a greater problem in circumstances where romantic love is quick to arise. Mate choice, by definition, excludes other potential mates and romantic love, in fact, suppresses the search for other mates ( Fletcher et al., 2015 ). This cost can be exacerbated in certain environments such as those within which finding additional mates is relatively easy ( Kushnick, 2016 ). Romantic love can detract from other fitness-promoting goals such as career-advancing activities, physical health promoting activities, or forming and maintaining other social relationships.

Romantic love serves a courtship function ( Fisher et al., 2006 , 2016 ). Courtship involves a series of signals and behaviors that serve as a means of assessing potential partner quality and willingness to invest in a relationship ( Trivers, 1972 ; Wachtmeister and Enquist, 2000 ). One function of the attraction system is to pursue potential mates ( Fisher, 2000 ). People in love often engage in courtship of their loved one with the aim of persuading them that they are a good long-term mate.

The primary benefit of courtship in romantic love is that it can secure a mate that is prepared to commit to a relationship. To do this, both sexes can pursue potential mates, display commitment, and signal fidelity ( Buss, 2019 ). These acts are why love has been described as a commitment device ( Frank, 1988 ; Fletcher et al., 2015 ; Buss, 2019 ). Courtship allows individuals to learn about and assess the suitability of potential mates while displaying reproductively relevant resources ( Buss, 2019 ). Men emphasize characteristics such as resources, while women emphasize characteristics such as beauty, in an attempt to increase attractiveness ( Buss, 1988 ; Luoto, 2019a ). Men, at least historically, also provide signals of parental investment ( Buss, 2019 ). Literature on human courtship from an evolutionary perspective supports the notion of greater choosiness among females, predicted by parental investment theory ( Trivers, 1972 ), for short-term mating and less serious commitments. This effect, however, substantially diminishes for long-term mating endeavors and marriage commitment ( Kenrick et al., 1990 ). The literature also suggests that women are looking for specific cues, indicative of evolved preferences, during the courtship process ( Oesch and Miklousic, 2012 ).

There are costs associated with romantic love’s courtship function. These include the expenditure of a significant amount of time and resources and, if courtship efforts are not reciprocated, embarrassment ( Silver et al., 1987 ). Sometimes, individuals in love might engage in intrusive “obsessive pursuit” of someone who is not interested ( Spitzberg and Cupach, 2003 ). Courtship can be a particularly stressful time for an individual. There are also potential costs because individuals who are courting might find themselves in direct intrasexual competition with another individual who has an interest in their potential mate. Intrasexual competition can be costly because an individual must divert additional resources to this endeavor. An individual bears even greater costs if they lose this competition. Both sexes can be subject to costly signaling as part of courtship ( Griskevicius et al., 2007 ), although men are at risk of higher fitness costs associated with temporally extended courtships, despite this being interpreted as a sign of a good mate by women ( Seymour and Sozou, 2009 ).

Romantic love promotes sex and may increase the chances of pregnancy. Sex is an important part of romantic relationships and initiation into sex with a partner, and a greater frequency of sex, is associated with the earlier stages of a romantic relationship ( Call et al., 1995 ). Sex and pregnancy are not, however, features of romantic love in pre-pubescent children and pregnancy is not a feature of romantic love in post-menopausal women. The nature of reproduction is different in societies where contraception and family planning practices are widespread (see Goetz et al., 2019 , for review of evolutionary mismatch in human mating). In such circumstances, immediate pregnancy may not be a feature of romantic love, whereas sex often is. In such circumstances, romantic love may indirectly promote pregnancy by creating pair-bonds whose members later reproduce.

Romantic love provides sexual access ( Buss, 2019 ). Love is one of the most common reasons people give for having sex ( Ozer et al., 2003 ; Meston and Buss, 2007 ; Dawson et al., 2008 ; Meston and Buss, 2009 ). Given the relative willingness of men to engage in short-term mating compared to women, it follows that sex because of love plays a greater role in providing sexual access by women to men than the other way around ( Meston and Buss, 2007 ). Sex can facilitate a gain in reputation ( Meston and Buss, 2007 ) and both sexes increase their status by having children ( Buss et al., 2020 ). Sex is intrinsically pleasurable and reinforcing, and promotes bonding ( Meltzer et al., 2017 ). In times before the advent of contraception, repeated sex with a partner would usually result in pregnancy and childbirth ( Goetz et al., 2019 ; Kushnick, 2019 ). This is still the case in many parts of the world.

For example, there is evidence that features characteristic of romantic love may be associated with a greater number of children among the Hadza, a hunter gatherer tribe in northern Tanzania ( Sorokowski et al., 2017 ). Higher passion, which is definitive of romantic love (e.g., Sternberg, 1986 ), is associated with a greater number of children in women. The findings are important because the lifestyle of the Hadza more closely resembles the environment in which humans evolved than do industrialized or agrarian societies. As a result, inferences can be made about the adaptive function of passion in human evolutionary history. However, intimacy, another component of romantic love ( Sternberg, 1997 ), was found to be negatively correlated with number of children in women. Instead, commitment, a feature of companionate love, was associated with greater number of children in both women and men ( Sorokowski et al., 2017 ). Romantic love is normally relatively short-lived, and therefore the methods used in this study may not have been ideally suited to investigate the fitness consequences of romantic love. Nonetheless, this finding provides some support for the notion that romantic love promotes sexual access by women and facilitates reproduction.

One study ( Sorokowski et al., 2019 ) suggests that romantic love may increase the likelihood of a woman falling pregnant. Higher levels of the gonadotropins, follicle-stimulating hormone, and luteinizing hormone, and a non-significant but positive increase in estradiol to testosterone ratio in women experiencing romantic love could cause increased ovarian activity and increased estradiol synthesis, which might result in higher fecundity ( Sorokowski et al., 2019 ).

The costs associated with romantic love’s sex function are far greater for women than for men ( Trivers, 1972 ). Both sexes could be subject to unwanted pregnancy and associated parenting responsibilities (although this impacts women to a greater extent). There is also, however, a risk of damage to an individual’s reputation. Women are often subject to criticism from other women for engaging in sexual activity ( Koehn and Jonason, 2018 ), especially if a long-term relationship does not result. Men and women risk damage to their reputation for having sex with a low mate value partner, although men are generally treated far more favorably than women for engaging in sexual activity (see Zaikman and Marks, 2017 ). For women, a period of pregnancy followed by a lengthy period of lactation may ensue, and this is costly in terms of the ability to obtain sufficient resources and protecting oneself from harm. There is also the possibility that the relationship will dissolve following pregnancy and the woman may be left to raise a child without the father’s support ( Koehn and Jonason, 2018 ).

Pair-Bonding

Romantic love serves a pair-bonding function ( Fletcher et al., 2015 ). Pair bonding is both a process and a sate characterized by the formation of “enduring, selective attachments between sexual partners” ( Young et al., 2011 , p. 1). It differs from established pair-bonds and the neural characteristics of people experiencing romantic love differ somewhat from what is associated with longer-term pair-bonds (see Acevedo et al., 2012 , for distinction). Evolutionarily, when sex more often led to pregnancy, this pair-bonding would occur in the context of pregnancy and childbirth (although it is unclear if romantic love can exist at the same time as mother-infant bonding). This is still the case in many parts of the world. This is one possible reason for the duration of reciprocated romantic love to be between 18 months and 3 years ( Tennov, 1979 ) when not interrupted by childbirth. The intensity of specific neural activity in people experiencing romantic love is associated with relationship maintenance ( Xu et al., 2012a ).

Romantic love can establish long-term pair-bonds. In both sexes, romantic love promotes the provision of psychological and emotional resources ( Buss, 2019 ) as well as other types of caregiving ( Fletcher et al., 2015 ). It promotes relationship exclusivity through fidelity, jealousy, and mate-guarding ( Buss, 2019 ). Both sexes engage in additional mate retention tactics such as vigilance, mate concealment, monopolization of time, resource display, love and care, or sexual inducements ( Buss et al., 2008 ). Romantic love also promotes the sharing of other resources such as food or money. This benefit for women would have been, and often continues to be, greatest during times of lactation (see Marlowe, 2003 ; Quinlan, 2008 ). Both sexes can also benefit reputationally, as being in a relationship with a high mate value individual confers status, and individuals who are married or in a relationship are viewed more favorably than single people ( DePaulo and Morris, 2006 ). Men experiencing romantic love engage in actions that lead to successful reproductive outcomes ( Buss, 2019 ), such as protecting partners from physical harm. Men also engage in parenting ( Geary et al., 2004 ; Bribiescas et al., 2012 ), which could potentially result in increased offspring survival ( Fletcher et al., 2015 ).

When people are experiencing romantic love they are usually, but not always, interested in pursuing a “long-term mating strategy.” A long-term mating strategy is one that involves commitment, pair-bonding, and the parental investment (if children result) of both partners ( Buss, 2006 ). This contrasts with short-term mating strategies that do not often require public commitment, pair-bonding, and parental investment of the father ( Buss and Schmitt, 1993 ). Pair-bonding is characteristic of a long-term mating strategy.

The concept of romantic love serving as a commitment device is relevant to pair-bonding, as are the concepts of fitness interdependence ( Buss, 2019 ) and self-expansion. Fitness interdependence is the degree to which two people influence each other’s success in replicating their genes ( Aktipis et al., 2018 ). Romantic love binds two individuals together so that the potential reproductive success of one person is contingent upon the success of the other. The self-expansion model suggests that “people seek to expand their potential efficacy to increase their ability to accomplish goals” and that “one way people seek to expand the self is through close relationships, because in a close relationship the other’s resources, perspectives, and identities are experienced, to some extent, as one’s own” ( Aron and Tomlinson, 2019 , p. 2). Fitness interdependence and self-expansion can be increased in people experiencing romantic love.

There are substantial costs associated with pair-bonding ( Kushnick, 2016 ; Klug, 2018 ). Both sexes are potentially missing out on long-term mating opportunities with other suitable mates and are more restricted in terms of short-term mating opportunities ( Geary et al., 2004 ). There is a potential for damage to an individual’s reputation if they are in a relationship with a low mate value individual ( Buss, 2016 ). Both sexes share resources. Pair-bonding is associated with a reduction in the size of an individual’s support network ( Burton-Chellew and Dunbar, 2015 ). Jealousy can have negative effects upon a relationship ( Buss, 2000 , 2019 ; Hatfield et al., 2016 ) and there is a potential for emotional or physical harm arising from a relationship. People sometimes engage in homicide of their current or former partners in response to infidelity, or as a result of jealousy or a breakup ( Buss, 2000 , 2019 ; Shackelford et al., 2003 ). Some women engage in this behavior, but it is predominately a male behavior, when it occurs ( Buss, 2019 ). Stalking can occur following a breakup ( Spitzberg and Cupach, 2003 ; Buss, 2019 ) or, more generally, as a result of romantic love ( Marazziti et al., 2015 ). There is the potential for grief or depression symptoms following the breakup of a relationship ( Verhallen et al., 2019 ). Changing living arrangements, dividing up resources, and legal costs could all be necessary following the dissolution of a pair-bond ( Bear and Rand, 2019 ). Sex-specific costs include sexual obligations to a partner from women and parental investment by men ( Geary et al., 2004 ; Luoto, 2019a ).

While there is evidence that successful pair-bonding is associated with better health and survival ( Fletcher et al., 2015 ), there is little evidence showing that romantic love is associated with good health. Falling in love is associated with alteration in immune cell gene regulation in young women ( Murray et al., 2019 ). Specifically, falling in love is associated with genetic changes that could potentially result in an up-regulation of immune responses to viruses.

Experiencing romantic love for a recently gained partner is associated with the “active/elated” symptoms of hypomania ( Brand et al., 2007 , 2015 ). These symptoms are considered as favorable, “bright side” symptoms and contrast with unfavorable “dark side” symptoms such as disinhibition/stimulation-seeking and irritable/erratic dimensions ( Brand et al., 2015 ). Despite their association with hypomania, the favorable nature of these symptoms in romantic love may be a sign of good physical and mental health because higher hypomanic scores have been associated with higher “mental toughness,” increased physical activity, lower symptoms of depression, and lower sleep complaints ( Jahangard et al., 2017 ). Additionally, falling in love with a partner is sometimes associated with a reduction in depressive symptoms ( Bajoghli et al., 2013 , 2017 ). A reduction in the number of sexual partners could result in a decreased risk of sexually transmitted infections. There is evidence that romantic love might sometimes be associated with improved sleep quality ( Brand et al., 2007 ; Bajoghli et al., 2014 ).

There are some health-related costs associated with romantic love for both sexes. Despite a reduced risk of sexually transmitted infections being a benefit of romantic love, engaging in sexual activity at all may represent an increased risk of sexually transmitted infection, resulting in a cost to some ( Buss, 2016 ; Koehn and Jonason, 2018 ). Infertility from sexually transmitted infections is possible among women ( Koehn and Jonason, 2018 ). Disinhibited/stimulation-seeking and irritable/erratic, depressed, and anxious mood are sometimes features of romantic love ( Wang and Nguyen, 1995 ; Bajoghli et al., 2013 , 2014 , 2017 ; Brand et al., 2015 ; Kuula et al., 2020 ). In the face of repeated unrewarding efforts or adverse events in the courtship process, depressed or anxious mood could result ( Nettle and Bateson, 2012 ). Romantic rejection can result in a major depressive episode or even suicide (see Rantala et al., 2018 ). Despite evidence of improved sleep quality in people experiencing romantic love in some studies ( Brand et al., 2007 ; Bajoghli et al., 2014 ), one study ( Kuula et al., 2020 ) found poorer sleep quality, later sleep timing, and shorter sleep duration (one feature commonly found in studies relied upon to suggest a sleep quality benefit of romantic love) in adolescent girls experiencing romantic love. This suggests that altered sleep may in fact be a detrimental cost in some people experiencing romantic love. Women have the added risk of birth-related complications and death, which has been common in humans until recently in developed countries ( Goldenberg and McClure, 2011 ).

Selective Pressures

The literature contains three interesting theories of possible selective pressures for romantic love. They are framed in the context of promoting the evolution of pair-bonds, but as will be detailed below, the evolution of pair bonds and romantic love are likely to be inexorably linked. All three theories relate to the provision of resources by males to females. The first theory is that pair-bonds and romantic love may have emerged prior to 4 million years ago when bipedalism emerged and hominins moved into the woodlands and savannahs of our ancestral homelands (see Fisher et al., 2016 ). The need for mothers to carry infants in their arms may have driven them to select partners that were wired for pair-bonds which was associated with provisioning, defense, and other forms of support.

The second theory is that biparental care was a driving force in the emergence of long-term mating strategies ( Conroy-Beam et al., 2015 ). A game theoretical approach contends that females selecting males that were wired for pair-bonds directly increased the chances of offspring survival through the provisioning of tangible and intangible resources to the female and offspring. If biparental care was a driving force in the formation of pair-bonds in humans, it would be a uniquely human pressure, as biparental care has been generally identified as a consequence, rather than a cause, of pair-bonds in mammals ( Opie et al., 2013 ; Lukas and Clutton-Brock, 2013 ). This theory also has to contend with the fact that father presence is often not associated with better offspring survival in societies with little access to health care or contraception (see Fletcher et al., 2015 ).

The third theory is that a need for increased fecundity drove the selection of pair-bonds ( Conroy-Beam et al., 2015 ). Periods of malnutrition cause decreased fecundity. Once again, a game theoretical approach suggests that the selection of males that were wired for pair-bonds, which is associated with provisioning of females, increased the caloric intake of females over prolonged periods of time and, in turn, increased fecundity. This hypothesis is appealing because this selective pressure could have been present at any stage among the four hypotheses we propose for the emergence of pair-bonds in a section below.

Romantic Love Is a Complex Suite of Adaptations and By-Products

In evolutionary psychology, an adaptation is “…an inherited and reliably developing characteristic that came into existence as a feature of a species through natural selection because it helped to directly or indirectly facilitate reproduction during the period of its evolution” ( Buss et al., 1998 , p. 535; see also Williams, 2019 ). This approach is based, rightly, on the difficulty of testing hypotheses about the adaptive benefits of traits in ancestral environments. There is an equally valid approach, however, adopted by behavioral ecologists, that views current utility of adaptations as evidence that can be extrapolated to the past ( Fox and Westneat, 2010 ). One definition that has arisen from this approach is that “[a]n adaptation is a phenotypic variant that results in the highest fitness among a specified set of variants in a given environment” ( Reeve and Sherman, 1993 , p. 9).

Taken together, these two approaches to adaptation support the view that romantic love is a “complex suite of adaptations” ( Buss, 2019 , p. 42). The numerous mechanisms recruited in romantic love, the large number of psychological characteristics, and the multiple functions it serves suggest that romantic love may be an amalgamation of numerous adaptations that respond to a variety of adaptive challenges. However, while romantic love may comprise several inter-related adaptations, this does not preclude the possibility that some components are by-products. A by-product is a trait that evolved “not because it was selectively advantageous, but because it was inextricably linked…to another trait that was reproductively advantageous” ( Andrews et al., 2002 , p. 48).

Health-promoting benefits of romantic love, such as elevated mood, increased sleep quality, and up-regulated immune responses, for example, may be by-products of mood circuitry (see Nettle and Bateson, 2012 ; D’Acquisto, 2017 ; Jahangard et al., 2017 ) or other mechanisms, even though they offer some survival or reproductive advantage. Elevated mood, better sleep quality, and an associated up-regulated immune system probably evolved prior to the emergence of romantic love (see Flajnik and Kasahara, 2010 ; Loonen and Ivanova, 2015 ). As a result, it might be prudent to contend that romantic love is a complex suite of adaptations and by-products.

Further, while the evidence points to romantic love as a suite of adaptations and by-products, it is not adaptive in every context. Romantic love continues to have its reproduction-promoting functions in the modern world in some circumstances, either by immediately promoting reproduction, or indirectly promoting reproduction via the formation of romantic relationships, the members of which later reproduce. To that extent, romantic love is sometimes adaptive (see Laland and Brown, 2011 , for distinction between “adaptation” and “adaptive” and lists of benefits, above, for examples of how romantic love can be adaptive). There are circumstances when romantic love may be maladaptive, however, as is evidenced by the substantial fitness-relevant costs of romantic love detailed above. Cogent examples of this are when a loved one is already in a committed relationship or otherwise not interested, when an individual engages in obsessive pursuit that can have social or even legal ramifications, or when violence ensues.

When applied to romantic love, the fourth of Tinbergen’s (1963) four questions asks, “What is the evolutionary history of romantic love?” Phylogenetic explanations focus on the origin and maintenance of a trait in historical evolutionary terms ( Tinbergen, 1963 ; Bateson and Laland, 2013 ). They put a biological trait in a comparative perspective by focusing on the presence or absence of the trait in closely, and sometimes more distantly, related species. In this section, we describe the theory of independent emotion systems and articulate a theory of co-opting mother-infant bonding mechanisms. We examine the primitive structures related to romantic love that arose in our mammalian evolutionary past and were restructured in pair-bonded species. We also examine the particular history of pair-bonds, and thus romantic love, in hominin evolution, with a comparison to other species of primates, especially apes. Finally, we examine the effect of gene-cultural evolutionary issues with regard to romantic love.

Independent Emotion Systems

Fisher’s ( 1998 , 2000 , see also Fisher et al., 2002 ) evolutionary theory of independent emotions systems delineates sex drive (lust), attraction (romantic love), and attachment (pair-bonds). Sex drive is primarily associated with estrogens and androgens and serves to motivate individuals to engage in sexual activity, generally. Attraction is primarily associated with the catecholamines (i.e., dopamine and norepinephrine), phenylethylamine, and serotonin and serves to focus efforts on preferred mating partners. Attachment is primarily associated with oxytocin and vasopressin and serves to enable individuals to engage in positive social behaviors and connections of a sufficient length of time to satisfy species-specific parenting approaches ( Fisher, 1998 ). Sex drive relates most to the sex function of romantic love, attraction to the mate choice and courtship functions, and attachment to the pair-bonding function. Romantic love shares similarities with the ‘courtship attraction system’ found in many mammals ( Fisher et al., 2006 ).

Co-opting Mother Infant Bonding Mechanisms

While the theory of independent emotion systems ( Fisher, 1998 , 2000 ; Fisher et al., 2002 ) has been the predominate theoretical account of the evolution of romantic love for more 20 years, comparative studies, imaging studies, and assessments of psychological characteristics have raised the possibility of a complimentary evolutionary theory, that of co-opting mother-infant bonding mechanisms. Literature on romantic love, maternal love (of which mother-infant bonding is a part), mother–infant bonding, and pair-bonding ( Bartels and Zeki, 2004 ; Ortigue et al., 2010 ; Numan and Young, 2016 ; Walum and Young, 2018 ) suggests romantic love may have evolved by co-opting mother-infant bonding mechanisms. Co-option is an evolutionary process whereby a trait (e.g., mechanism, morphology, behavior) is repurposed – that is, it serves a different function to that which it originally served (see McLennan, 2008 ).

Animal research, focusing on mammals, and involving, monogamous prairie voles, finds substantial similarities between mother-infant bonding mechanisms and pair-bonding mechanisms ( Numan and Young, 2016 ). “[A]mygdala and nucleus accumbens–ventral pallidum (NA–VP) circuits are involved in both types of bond formation, and dopamine and oxytocin actions within NA appear to promote the synaptic plasticity that allows either infant or mating partner stimuli to persistently activate NA–VP attraction circuits, leading to an enduring social attraction and bonding” ( Numan and Young, 2016 , p. 98). Some of these circuits do not appear to be involved in human romantic love, but there are other similarities that support a theory of co-opting mother-infant bonding in humans.

Several brain regions implicated in romantic love overlap precisely with that involved in maternal love. This includes activity in numerous regions that are associated with a high density of oxytocin and vasopressin receptors ( Bartels and Zeki, 2000 , 2004 ) although it should be noted that in the study that asserts this, participants included mothers experiencing maternal love beyond the mother-infant bonding stage. A meta-analysis of love also found romantic and maternal love shared activity in dopamine-rich areas ( Ortigue et al., 2010 ). Almost nothing is known about the mechanisms regulating the infant side of mother-infant bonding. However, some inferences have been made from animal models which suggest that the mechanisms may be similar to those regulating the maternal side, but without involvement of the amygdala (see Sullivan et al., 2011 , for review).

There are substantial psychological similarities between romantic love and early parental love, of which mother–infant bonding is a part. Extreme similarities exist between romantic love and early parental love in the domains of altered mental state, longing for reciprocity, idealization of the other, and dichotomous resolution of the establishment of intimate mutually satisfying reciprocal patterns of interaction usually marked by a culturally defined ritual ( Leckman and Mayes, 1999 ). Similar trajectories of preoccupation in romantic love and parental love also exist. In romantic love, preoccupation increases through the courtship phase and peaks at the point of reciprocity where preoccupation begins to slowly diminish. In parental love, preoccupation increases throughout pregnancy and peaks at the point of birth where preoccupation begins to diminish.

Mammalian Antecedents

Romantic love in humans is caused by physiological mechanisms whose evolutionary roots were planted in our early mammalian ancestors. These evolutionary roots provided the raw materials that were fleshed out, in evolutionary time, to form the basis of a wide range of social behaviors in mammals, including those related to sex drive, mate choice, and attachment ( Fisher, 1998 , 2000 ; Fisher et al., 2002 ; Broad et al., 2006 ; Carter and Perkeybile, 2018 ; Curley and Keverne, 2005 ; Fisher et al., 2006 ; Fischer et al., 2019 ; Johnson and Young, 2015 ; Numan and Young, 2016 ; Porges, 1998 ). Romantic love may have evolved after the neural circuitry associated with mate choice became populated by oxytocin receptors which played a role in the evolution of enduring social attraction and pair-bond formation (see Numan and Young, 2016 ). “[P]air bonding is the evolutionary antecedent of romantic love and…the pair bond is an essential element of romantic love” ( Walum and Young, 2018 , p. 12).

Examining the similarities between the neurobiological and endocrinological mechanisms involved in mother-infant bonding and pair-bonding in mammals, it becomes apparent that the maternal functions of this suite of adaptations arose deep in the evolutionary history of mammals ( Numan and Young, 2016 ). Their derived, pair-bonding functions would have arisen later in a very small number of species (only 3–5% pair-bond). As such, the neural circuitry and other proximate mechanisms involved in mother-infant bonding in mammals “may have provided a primordial neural scaffold upon which other types of strong social bonds, such as pair bonds, have been built” ( Numan and Young, 2016 , p. 99). We are, thus, on reasonably solid ground to posit evolutionary trajectories of romantic love. Figure 1 presents information and hypotheses about the evolutionary history of romantic love. Evolutionary trajectories of romantic love start with the ancestral mammalian mother–infant bonding mechanisms and culminate in their co-option and modification for pair-bonding in several mammalian lineages ( Numan and Young, 2016 ). Human romantic love results from one of these trajectories. In another trajectory—the one that includes pair-bonding prairie voles ( Microtus ochrogaster )—we know quite a lot about the functioning of oxytocin, vasopressin, and dopamine in facilitating pair-bonding (e.g., Carter and Getz, 1993 ; Carter and Perkeybile, 2018 ; Walum and Young, 2018 ). Although these derived changes to the primitive mammalian machinery may not be the direct evolutionary antecedents of those at work in humans (they are, rather, the product of parallel evolution), they provide a window into how basic machinery can be modified to affect those ends. One substantive difference appears to be the relative importance of the hormonal drivers in the smaller species, and the dopamine-related ones in humans ( Broad et al., 2006 ; Fisher et al., 2016 ).

Figure 1. Phylogenetic relationships among select mammal species that pair-bond.

Pair-Bonds in Primates

Humans are members of the primate superfamily Anthropoidea, amongst whom there is great diversity in social systems, and whose ancestral state likely included complex group-based social relationships ( Kay et al., 1997 ; Shultz and Dunbar, 2007 ). This would have included long-term association between unrelated males and females—which is a far cry from the solitary system that is modal and ancestral for mammals ( Lukas and Clutton-Brock, 2013 ; Opie et al., 2013 ). There are even some members of this lineage who have evolved pair-bonds, such as the marmosets and tamarins (Callitrichidae), and gibbons (Hylobatidae). The similarities between these species and humans in terms of the adaptive suite related to pair-bonds, like the similarities between humans and voles, are due to convergent/parallel evolution ( French et al., 2018 ).

Our closest living relatives are the common chimpanzee ( Pan troglodytes ) and bonobo ( Pan paniscus ) with whom we share a common ancestor just 5–8 million years ago. While bonobos are alluring due to their free-willed sexual nature, common chimpanzees provide a better glimpse into the behavior of our direct ancestors. Although the common chimpanzee mating system is defined as promiscuous, there are, in fact, three forms of common chimpanzee mating tactics ( Morin, 1993 ). The first two—possessive mating and consortships—involve some of the characteristics we associate with romantic love, such as a more-than-fleeting association and mate guarding, but they are much rarer than the third type, opportunistic mating. The comparison of chimpanzees and humans, thus, suggests that one possible hypothesis for the emergence of romantic love is that it originated in their common ancestor (H1 in Figure 1 ). Alternatively, it might be that the common ancestor had an adaptive repertoire that was primed for its emergence when the requisite socioecological context arose. In this way, the evolution of romantic love from chimp-like mating is similar to the evolution of human culture from chimp-like culture.

For some, the origin of romantic love was more likely to have fallen somewhere on our side of the human–chimpanzee split (e.g., Fisher et al., 2016 ). Even so, we are left with the difficulty of pinpointing exactly when it arose—attributable to there being only one extant hominin species from amongst the many that have existed ( Pigliucci and Kaplan, 2006 ) and the lack of direct fossil evidence for romantic love. If we accept the conventional view that romantic love evolved to facilitate pair-bonding, then we can search for clues about the evolution of the former by tracing the evolution of the latter ( Fletcher et al., 2015 ). A transition from ape-like to human-like sexual behavior in our lineage may have pre-dated the emergence of the genus Homo ( Lovejoy, 1981 )—and, thus, we have a second hypothesis (H2 in Figure 1 ). A comparison of sexual dimorphism in Australopithecus and early genus Homo , however, suggests a third hypothesis—that it arose after their emergence (H3 in Figure 1 ). Several lines of evidence suggest that the earliest members of our species, Homo sapiens , pair-bonded but were not necessarily monogamous. Based on an examination of the distribution of mating systems in modern, small-scale human societies and three correlates of primate mating systems ( Dixson, 2009 ), it is possible to conclude that pair-bonds are a “ubiquitous” feature of human mating that can manifest through polygyny or polyandry, but most commonly occur in the form of serial monogamy ( Schacht and Kramer, 2019 ). The final hypothesis, thus, is that romantic love is the unique domain of our species (H4 in Figure 1 ).

The transition to mostly monogamous and some polygynous groupings could have had a transitional phase where polygynous groupings were the norm ( Chapais, 2008 , 2013 ). Pair-bonds may have arisen from a complex interaction between the fitness benefits and costs of mating and parental care ( Quinlan, 2008 ). The transition from ape-like promiscuity to human pair-bonds may have been driven by the provision of females by low-ranking males ( Gavrilets, 2012 ). The direct benefits for females was the food provided, for the males, the mating opportunity. This may have led to selection for males that were less aggressive and more prosocial. The female mate-choice mechanism is a distinct possibility for explaining human self-domestication ( Gleeson and Kushnick, 2018 ).

Gene-Culture Coevolution

Romantic love is a universal or near-universal feature in human societies ( Jankowiak and Fischer, 1992 ; Gottschall and Nordlund, 2006 ; Jankowiak and Paladino, 2008 ; Fletcher et al., 2015 ; Buss, 2019 ; Sorokowski et al., 2020 ). A small number of genetic correlation studies show that there are a number of genes associated with romantic love ( Emanuele et al., 2007 ; Murray et al., 2019 ; Acevedo et al., 2020 ). Other insights into the genetic evolution of romantic love can be garnered from elsewhere, however. For example, life history theory provides insight into ethnic or geographical variation in romantic love and its role in providing sexual access by women.

Romantic love is among the most common reasons female adolescents give for having sex ( Ozer et al., 2003 ). A “slow” life history strategy is associated with eros more than other loving styles ( Marzec and Łukasik, 2017 ). Psychopathology associated with impulsivity is a feature of a “fast” life history strategy, as is promiscuous sexuality ( Del Giudice, 2016 ). Greater impulsivity is associated with a reduced likelihood of giving romantic love as a reason for having sex among adolescent females ( Dawson et al., 2008 ).

As a result, genetic determinants of life history strategies (e.g., Figueredo et al., 2004 ) may influence the occurrence of romantic love. National scores on the life history strategy genetic factor index correlate with adolescent fertility rates indicating that genetic predictors of a fast life history are associated with higher rates of adolescent pregnancy ( Luoto, 2019b ). This ethnic or geographical variation in the genetic determinants of life history strategies may also represent ethnic or geographic variation in the genetic determinants and reproductive relevance of romantic love.

In addition to this, cultural factors may have affected the role of romantic love in mating and marriage decisions—and this has implications for understanding the evolution of romantic love ( Fletcher et al., 2015 ). Arranged marriages are the norm in 80% of 200 forager societies from the Ethnographic Atlas ( Apostolou, 2007 ). Phylogenetic methods to reconstruct the ancestral marriage patterns of our species using the same data found that there were likely marriage transactions (brideprice or brideservice) but only a limited amount of polygyny ( Walker et al., 2011 ). While the ancestral state for arranged marriages was not definitive, arranged marriages were likely present around 50 thousand years ago, when our ancestors expanded their range beyond Africa. So, despite romantic love being viewed as an important component of marriage and mating, it may have played a role of decreasing importance in the recent evolutionary history of our species. Arranged marriages may have limited the role of female mate choice in intersexual selection ( Apostolou, 2007 ). Further, despite romantic love’s decreased role in courtship and marriage, it may have continued to serve a role in facilitating pair-bonding as romantic love can develop even in the arranged-marriage context. The role of romantic love in facilitating mate choice, courtship, and marriage may now be increasing with the decline and modification of arranged marriages in many parts of the world (e.g., Allendorf and Pandian, 2016 ). This may be the result of the increasing sexual equality of women (e.g., de Munck and Korotayev, 1999 ).

Romantic love is a complex and multifaceted aspect of human biology and psychology. Our approach in this review has been to highlight how Tinbergen’s (1963) “four questions” can help us to synthesize the important strands related to the mechanisms, development, fitness-relevant functions, and evolutionary history of this phenomenon. Here, we synthesize what this review has presented in each level of explanation and suggest what this indicates about other levels of explanation. We then highlight some gaps in our knowledge that could be filled with future research and present a new ethologically informed working definition of romantic love.

What Do Tinbergen’s Four Questions Tell Us?

One of the benefits of using Tinbergen’s four questions as a framework to describe a complex trait such as romantic love is its ability for one level of explanation to provide insights into the other level of explanation (see Tinbergen, 1963 ; Bateson and Laland, 2013 ; Zietsch et al., 2020 ). In particular, an understanding of the proximate causes of romantic love has provided insights into the functions and phylogeny of romantic love although an understanding of the ultimate level of explanation provides some insights into the mechanisms of romantic love.

Multiple mechanistic systems involved in romantic love suggests it may serve multiple functions and may be a suite of adaptations and by-products rather than a single adaptation. We found that romantic love is associated with activity in a number of neural systems: reward and motivation, emotions, sexual desire and arousal, and social cognition. It is also associated with activity in higher-order cortical brain areas that are involved in attention, memory, mental associations, and self-representation. We also found that romantic love is associated with a number of endocrine systems: sex hormones, serotonin, dopamine, oxytocin, cortisol, and nerve growth factor. This is consistent with our position that romantic love serves mate choice, courtship, sex, and pair-bonding functions. Reward and motivation system activity may be particularly involved in the mate choice function of romantic love. Cortisol may be particularly indicative of the courtship function of romantic love, which overlaps with pair-bonding. Neural areas associated with sexual desire and arousal and the activity of sex hormones may play a particular role in the sex function. Finally, reward and motivation regions of the brain (rich with oxytocin receptors) and activity of the oxytocin system may play a particular role in the pair-bonding function of romantic love. Our understanding of the biological mechanisms that cause romantic love supports our description of romantic love’s functions.

Mechanistic similarities between romantic love and mother-infant bonding suggest that romantic love may have evolved by co-opting mother-infant bonding mechanisms. This articulates one hypothesis about the evolutionary history of romantic love that complements the predominate theory of independent emotion systems ( Fisher, 1998 , 2000 ; Fisher et al., 2002 ). This is supported by the psychological similarities between romantic love and early parental love.

Evidence of substantial activity of oxytocin receptor rich brain regions and the oxytocin endocrine system in romantic love lends weight to the position that romantic love only evolved after the neural circuitry associated with mate choice, specifically, regions of the mesolimbic reward pathway and dopamine rich areas, became populated by oxytocin receptors specifically receptive to stimuli from mating partners. That played a role in the evolution of enduring social attraction and pair-bond formation ( Numan and Young, 2016 ). This supports our claim that romantic love probably evolved in conjunction with pair-bonds in humans. As a result, we are bolstered when we contend that romantic love emerged relatively recently in the history of humans.

The duration of romantic love also raises questions about the functions of romantic love. It has been said that the psychological features of romantic love can last from 18 months to 3 years in reciprocated romantic love. However, in our evolutionary history, romantic love would have usually occurred in the context of pregnancy and child birth. Mother-infant bonding becomes active around the time of childbirth. We are not aware of any research that has investigated whether romantic love can occur at the same time as mother-infant bonding or whether it must subside for mother-infant bonding to become active. Answering this question would elucidate if the functions of romantic love extinguish once reproduction has been successful. The existence of long-term romantic love also raises questions about the functions of romantic love. It has been posited that long-term romantic love is “part of a broad mammalian strategy for reproduction and long-term attachment” ( Acevedo et al., 2020 , p. 1). This may indicate that long-term romantic love serves similar functions to romantic love that lasts a shorter period of time.

Just as the multiple biological mechanisms involved in romantic love suggests a variety of functions, the functions of romantic love specified in our review suggests specific biological mechanisms are involved. As outlined above, specific functions may be associated with specific mechanisms and this should be an area of targeted research.

The possibility of romantic love evolving by co-opting mother-infant bonding mechanisms raises a number of possibilities in relation to the proximate causes of romantic love. It suggests that social activity associated with mother–infant bonding (e.g., filling of needs, specific cues) may be particularly important precursors to, or features of, romantic love. It suggests that many of the genes and polymorphisms involved in causing romantic love may have been present in mammals since the emergence of mother–infant bonding, making comparative animal research using mammals relevant. It also suggests that further research into shared neural activity between romantic love and mother–infant bonding is warranted.

We contend that romantic love probably emerged in conjunction with pair-bonds in humans or human ancestors. As such, further information about the similarities and differences between romantic love (pair-bonding) and companionate love (established pair-bonds) is needed. In particular, information about any role of the mesolimbic pathway (see Loth and Donaldson, 2021 ) or regions associated with sexual desire in companionate love would help to shed light on the evolutionary history of pair-bonding and pair-bonds. Specifically, this could shed light on if, as has been suggested (see Walum and Young, 2018 ), romantic love and pair-bonds are inextricably linked.

Areas of Future Research

One issue with research into the mechanisms of romantic love is that it has, with some exceptions (e.g., Fisher et al., 2010 ), utilized samples of people experiencing romantic love who are in a relationship with their loved one. Romantic love serves a mate choice and courtship function, and as a result, a large proportion of people experiencing romantic love are not in a relationship with their loved one (e.g., Bringle et al., 2013 ). A small number of studies have directly investigated unrequited love (e.g., Tennov, 1979 ; Baumeister et al., 1993 ; Hill et al., 1997 ; Aron et al., 1998 ; Bringle et al., 2013 ), but none of these investigated the mechanisms that cause romantic love. Studying such people might identify the specific contributions of particular mechanisms to particular functions. For example, the mechanisms associated with the pair-bonding function of romantic love may not be active in individuals who are engaging in courtship and the mechanisms involved in courtship may not be present in lovers who are already in a relationship with their loved one. Research would benefit from considering the mechanisms that underlie related psychopathologies and it would be useful to understand the relationship between mate preferences and romantic love.

Molecular genetics research, such as that undertaken by Acevedo et al. (2020) , could further identify contributions of genes in people experiencing romantic love. Resting state fMRI provide an opportunity to investigate networks characteristic of psychopathology related to romantic love. Research should investigate the automatic/internal emotional regulatory network and the volitional/external regulatory network associated with mania/hypomania in people experiencing romantic love. Further research is required into the endocrinology of romantic love. In particular, further research is needed into the role of opioids, corticotropin-releasing factor, glutamate, acetylcholine, and vasopressin in romantic love. Efforts should be made to combine psychological and mechanisms research. For example, differences in neural or endocrine activity may be present in people experiencing romantic love who display elevated symptoms of depression compared to those who display reduced symptoms. As a result, neuroimaging and endocrinological studies could categorize people experiencing romantic love according to their levels of depression or type of hypomanic symptoms.

Given the large number of fMRI studies, interpreting the neuroimaging literature can be overwhelming. It has been nearly 10 years since the last meta-analysis of fMRI studies including romantic love. It is time for another one that focuses solely on romantic love. There is also a pressing need to attempt to replicate and extend endocrine studies and to specifically investigate the oxytocin system in people experiencing romantic love using validated measures of romantic love. As with many areas of psychological research ( Henrich et al., 2010 ), and specifically in areas related to mating psychology ( Apicella et al., 2019 ; Scelza et al., 2020 ), there is a pressing need to ensure that samples used in research are not exclusively Western, educated, industrialized, rich, and democratic.

Limited ontogeny research has elucidated the mechanisms causing romantic love across the lifespan. The literature that has (e.g., Luoto, 2019a ), has focused on mate choice, rather than romantic love, per se . We know nothing about the neurobiology or endocrinology of romantic love in children or about the endocrinology of long-term romantic love. It would be useful to investigate how the functions of romantic love differ according to age of individuals or the duration of romantic love. Internal and external factors influence romantic love, although there has been surprisingly little research into this topic. It would be prudent to continue to develop a more detailed understanding of the factors that lead to romantic love (e.g., Riela et al., 2010 , 2017 ). It would be useful to better understand the relationship between attachment styles and romantic love. Research should investigate if romantic love can occur at the same time as mother-infant bonding, or if they are mutually exclusive states.

Research into the functions of romantic love is sparse. There is a need for clear, evidence-informed definitions and descriptions of each of the functions of romantic love. It is likely that different mechanisms moderate different functions, and research should attempt to determine the contribution of specific genetic, neural, and endocrine activity to each individual function (see Zietsch et al., 2020 ). The advent of contraception and the adoption of family planning strategies means romantic love now serves more of a sex function than a pregnancy function in some environments. This is particularly the case early in a relationship. Pregnancy may become a feature as a relationship progresses and the fitness consequences of romantic love need to be investigated. Romantic love’s role as a suite of adaptations and by-products should be investigated. There is theoretical support for the notion that romantic love serves a health-promoting function (e.g., Esch and Stefano, 2005 ); however, there is a limited number of studies demonstrating a health-promoting effect of romantic love.

The relative infancy of genetic research, the lack of a clear fossil record, and the small number of species with which comparative analysis can be undertaken, means novel and creative means of investigating the phylogeny of romantic love must be undertaken. There is a need to pin-point the phylogenetic emergence of romantic love and the factors that caused it. To do this, more research into the genetics of romantic love must be conducted, and this should consider the phylogeny of specific genes and polymorphisms (e.g., Acevedo et al., 2020 ; see also Walum and Young, 2018 ). Efforts to assess the contribution of sexual selection to the evolution of romantic love are warranted. Studies of newly discovered fossils can help to identify shifts in sexual dimorphism that are indicative of pair-bonds. Further observational and experimental research into romantic love in hunter-gatherer tribes could tell us more about how romantic love functioned in our evolutionary history. Comparative research still has much to contribute. Research should explore the possibility that initial changes to the ancestral mammalian physiology that led directly to human romantic love arose in response to selection on both mating and non-mating-related behavior, such as pro-sociality (e.g., Barron and Hare, 2020 ; Luoto, 2020 ) or unique aspects of our species’ parenting repertoire. It might be fruitful to further investigate the relationship between romantic love and life history theory (e.g., Olderbak and Figueredo, 2009 ; Marzec and Łukasik, 2017 ). Finally, efforts should be made to elaborate and test the theory that romantic love emerged by co-opting mother–infant bonding mechanisms.

A New Working Definition of Romantic Love

The introduction to this review provided four definitions or descriptions of romantic love. For decades, most definitions ( Hendrick and Hendrick, 1986 ; Sternberg, 1986 ; Hatfield and Rapson, 1993 ) of romantic love have informed research into the cognitive, emotional, and behavioral characteristics of romantic love. The past two decades, however, have seen an increasing focus on the biology of romantic love. Only recently has an evolution-informed definition been proposed ( Fletcher et al., 2015 ). That working definition, however, does not incorporate much of the research that provides insight into the proximate and ultimate causes of romantic love.

We believe that the analytical approach taken in this review has identified sufficient information to justify the development of a new ethologically informed working definition of romantic love. The purpose would be to create an inclusive definition that is useful for researchers in varied disciplines investigating romantic love’s psychological characteristics, genetics, neurobiology, endocrinology, development, fitness-relevant functions, and evolutionary history. It may also be of use to psychologists and psychiatrists attempting to understand the experience and etiology of romantic love in their practice. It should be sufficiently precise and descriptive to both guide and link research. We provide, here, a working definition of romantic love:

Romantic love is a motivational state typically associated with a desire for long-term mating with a particular individual. It occurs across the lifespan and is associated with distinctive cognitive, emotional, behavioral, social, genetic, neural, and endocrine activity in both sexes. Throughout much of the life course, it serves mate choice, courtship, sex, and pair-bonding functions. It is a suite of adaptations and by-products that arose sometime during the recent evolutionary history of humans.

We situate the study of romantic love within the context of existing human mating literature. Our definition recognizes that romantic love is experienced across the lifetime of an individual, that research has shed light on the social, psychological, genetic, neural, and endocrine characteristics associated with it, and that it occurs in both sexes. Our definition also recognizes that romantic love serves a variety of functions and that these functions may vary across the lifespan. It does not exclude long-term or unrequited romantic love from the definition. Health is not identified as a function of romantic love in our definition despite being considered in our review. If more evidence comes to light, this definition can be amended to incorporate health.

Our definition has similarities and differences with the definition proposed by Fletcher et al. (2015) . This is appropriate given both are informed by evolutionary approaches which differ somewhat. We do not specifically define romantic love as being a commitment device or reference passion, intimacy, and caregiving. In our review, we recognize that romantic love is a commitment device and serves to display commitment and signal fidelity as part of its courtship function. We believe that reference to romantic love’s behavioral activity and courtship and pair-bonding functions sufficiently encapsulate this concept. Sternberg’s (1997) definition of romantic love and Fletcher et al.’s (2015) definition include references to passion and intimacy. Caregiving (e.g., provision of psychological and emotional resources, sharing resources), while associated with pair-bonding, is not sufficiently definitive of romantic love using Tinbergen’s four questions as a framework to include in our definition.

We do not reference the universality of romantic love. While some experts assert its universality (e.g., Fletcher et al., 2015 ; Buss, 2019 ), we believe that the finding of Jankowiak and Fischer (1992) leaves enough uncertainty for it to be prudent to omit this aspect from our definition. Their research has found no evidence of romantic love in fifteen cultures (see Jankowiak and Paladino, 2008 , for update to the original investigation) although this is probably the result of lack of data rather than evidence to the contrary. Once this matter is settled, which could be achieved by further investigating those societies where no evidence of romantic love was found, the definition can be amended. Fletcher et al. (2015) state that romantic love is associated with pair-bonds. We do the same by stating that pair-bonding is one of the functions of romantic love.

We also do not make specific reference to romantic love suppressing the search for mates. We recognize this as a cost in our review, but do not believe that this is so definitive of romantic love to include in our definition. Rather, we believe that our reference to “behavioral” activity and the “mate choice” function of romantic love in our definition sufficiently accommodates this feature. Our definition provides more detail than that provided by Fletcher et al. (2015) by including elements derived from substantial research into the mechanisms, ontogeny, functions, and phylogeny of romantic love. Like the Fletcher et al. (2015) definition, our definition recognizes that romantic love has distinct psychological characteristics and that we know about some of the proximate mechanisms that regulate it. However, as explained above, we do not include reference to the health-promoting effects of romantic love.

As more information about romantic love is gathered, we anticipate the definition to develop. However, we believe that this definition is an improvement upon previous definitions and adequately captures what is currently known about romantic love’s proximate and ultimate causes. It would be useful for researchers investigating romantic love from myriad perspectives. This definition should be critiqued and improved, and we welcome any such efforts from researchers and theorists across the spectrum of academic disciplines.

Our review provides a comprehensive account of the phenomenon known as romantic love. It covers topics such as social precipitants, psychology, genetics, neurobiology, and endocrinology. It provides an account of romantic love across the lifetime of an individual and is the first to propose four discrete reproduction-related functions of romantic love supported in the literature: mate choice, courtship, sex, and pair-bonding. It provides a summary of the benefits and costs of romantic love, outlines possible selective pressures, and posits that it is a complex suite of adaptations and by-products. We propose four potential evolutionary histories of romantic love and introduce the theory of co-opting mother-infant bonding mechanisms. We have identified a number of specific and general areas for future research. Our review suggests a new, ethologically informed working definition of romantic love that synthesizes a broad range of research. The working definition we propose serves to define a complex trait in a way that can both guide and link research from a variety of fields.

Author Contributions

AB conceived the manuscript. AB and GK collaborated on the development of the analytical framework and writing of the manuscript. Both authors approved the final version.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

We would like to thank the reviewers for comments that helped to improve the manuscript.

Supplementary Material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fpsyg.2021.573123/full#supplementary-material

Abler, B., Greenhouse, I., Ongur, D., Walter, H., and Heckers, S. (2008). Abnormal reward system activation in mania. Neuropsychopharmacology 33, 2217–2227. doi: 10.1038/sj.npp.1301620

PubMed Abstract | CrossRef Full Text | Google Scholar

Acevedo, B. P., and Aron, A. (2009). Does a long-term relationship kill romantic love? Rev. Gen. Psychol. 13, 59–65. doi: 10.1037/a0014226

CrossRef Full Text | Google Scholar

Acevedo, B. P., Aron, A., Fisher, H. E., and Brown, L. L. (2012). Neural correlates of long-term intense romantic love. Soc. Cogn. Affect. Neurosci. 7, 145–159. doi: 10.1093/scan/nsq092

Acevedo, B. P., Poulin, M. J., Collins, N. L., and Brown, L. L. (2020). After the honeymoon: neural and genetic correlates of romantic love in newlywed marriages. Front. Psychol. 11:634. doi: 10.3389/fpsyg.2020.00634

Adolphs, R. (2001). The neurobiology of social cognition. Curr. Opin. Neurobiol. 11, 231–239. doi: 10.1016/s0959-4388(00)00202-6

Aktipis, A., Cronk, L., Alcock, J., Ayers, J. D., Baciu, C., Balliet, D., et al. (2018). Understanding cooperation through fitness interdependence. Nat. Hum. Behav. 2, 429–431. doi: 10.1038/s41562-018-0378-4

Allendorf, K., and Pandian, R. K. (2016). The decline of arranged marriage? Marital change and continuity in India. Popul. Dev. Rev. 42, 435–464. doi: 10.1111/j.1728-4457.2016.00149.x

Aloe, L., Rocco, M. L., Balzamino, B. O., and Micera, A. (2015). Nerve growth factor: a focus on neuroscience and therapy. Curr. Neuropharmacol. 13, 294–303. doi: 10.2174/1570159x13666150403231920

Andersson, M., and Simmons, L. W. (2006). Sexual selection and mate choice. Trends Ecol. Evol. 21, 296–302. doi: 10.1016/j.tree.2006.03.015

Andrews, P. W., Gangestad, S. W., and Matthews, D. (2002). Adaptationism - how to carry out an exaptationist program. Behav. Brain Sci. 25, 489–504.

Google Scholar

Apicella, C., Norenzayan, A., and Henrich, J. (2019). Beyond WEIRD: a review of the last decade and a look ahead to the global laboratory of the future. Evol. Hum. Behav . 41, 319–329. doi: 10.1016/j.evolhumbehav.2020.07.015

Apostolou, M. (2007). Sexual selection under parental choice: the role of parents in the evolution of human mating. Evol. Hum. Behav. 28, 403–409. doi: 10.1016/j.evolhumbehav.2007.05.007

Arnold, A. P. (2020). Sexual differentiation of brain and other tissues: five questions for the next 50 years. Horm. Behav. 120, 104691. doi: 10.1016/j.yhbeh.2020.104691

Aron, A., Aron, E. N., and Allen, J. (1998). Motivations for unreciprocated love. Pers. Soc. Psychol. Bull. 24, 787–796. doi: 10.1177/0146167298248001

Aron, A., Dutton, D. G., Aron, E. N., and Iverson, A. (1989). Experiences of falling in love. J. Soc. Pers. Relationsh. 6, 243–257. doi: 10.1177/0265407589063001

Aron, A., Fisher, H., Mashek, D. J., Strong, G., Li, H. F., and Brown, L. L. (2005). Reward, motivation, and emotion systems associated with early-stage intense romantic love. J. Neurophysiol. 94, 327–337. doi: 10.1152/jn.00838.2004

Aron, A., and Tomlinson, J. M. (2019). “Love as expansion of the self,” in The New Psychology of Love ,eds. R. J. Sternberg and K. Sternberg 2nd Edn (United Kingdom: Cambridge University Press), 1–24. doi: 10.1017/9781108658225.002

Ayano, G. (2016). Dopamine: receptors, functions, synthesis, pathways, locations and mental disorders: review of literatures. J. Ment. Disord. Treat. 2, 120–124.

Bajoghli, H., Farnia, V., Joshaghani, N., Haghighi, M., Jahangard, L., Ahmadpanah, M., et al. (2017). “I love you forever (more or less)” - stability and change in adolescents’ romantic love status and associations with mood states. Rev. Brasil. Psiquiatr. 39, 323–329. doi: 10.1590/1516-4446-2016-2126

Bajoghli, H., Joshaghani, N., Gerber, M., Mohammadi, M. R., Holsboer-Trachsler, E., and Brand, S. (2013). In Iranian female and male adolescents, romantic love is related to hypomania and low depressive symptoms, but also to higher state anxiety. Int. J. Psychiatry Clin. Pract. 17, 98–109. doi: 10.3109/13651501.2012.697564

Bajoghli, H., Joshaghani, N., Mohammadi, M. R., Holsboer-Trachsler, E., and Brand, S. (2011). In female adolescents, romantic love is related to hypomanic-like stages and increased physical activity, but not to sleep or depressive symptoms. Int. J. Psychiatry Clin. Pract. 15, 164–170. doi: 10.3109/13651501.2010.549340

Bajoghli, H., Keshavarzi, Z., Mohammadi, M. R., Schmidt, N. B., Norton, P. J., Holsboer-Trachsler, E., et al. (2014). “I love you more than I can stand!” - romantic love, symptoms of depression and anxiety, and sleep complaints are related among young adults. Int. J. Psychiatry Clin. Pract. 18, 169–174. doi: 10.3109/13651501.2014.902072

Barron, A. B., and Hare, B. (2020). Prosociality and a sociosexual hypothesis for the evolution of same-sex attraction in humans. Front. Psychol. 10:2955. doi: 10.3389/fpsyg.2019.02955

PubMed Abstract | CrossRef Full Text

Bartels, A., and Zeki, S. (2000). The neural basis of romantic love. Neuroreport 11, 3829–3834. doi: 10.1097/00001756-200011270-00046

Bartels, A., and Zeki, S. (2004). The neural correlates of maternal and romantic love. Neuroimage 21, 1155–1166. doi: 10.1016/j.neuroimage.2003.11.003

Bateson, P., and Laland, K. N. (2013). Tinbergen’s four questions: an appreciation and an update. Trends Ecol. Evol. 28, 712–718. doi: 10.1016/j.tree.2013.09.013

Baumeister, R. F., Wotman, S. R., and Stillwell, A. M. (1993). Unrequited love - on heartbreak, anger, guilt, scriptlessness, and humiliation. J. Pers. Soc. Psychol. 64, 377–394. doi: 10.1037/0022-3514.64.3.377

Baumgarten, H. G., and Grozdanovic, Z. (1998). Role of serotonin in obsessive-compulsive disorder. Br. J. Psychiatry Suppl. 35, 13–20.

Bear, A., and Rand, D. G. (2019). Can strategic ignorance explain the evolution of love? Top. Cogn. Sci. 11, 393–408. doi: 10.1111/tops.12342

Belujon, P., and Grace, A. A. (2017). Dopamine system dysregulation in major depressive disorders. Int. J. Neuropsychopharmacol. 20, 1036–1046. doi: 10.1093/ijnp/pyx056

Berry, A., Bindocci, E., and Alleva, E. (2012). - NGF, brain and behavioral plasticity. - 2012. Neural Plast. 2012:784040.

Bindl, U. K., Parker, S. K., Totterdell, P., and Hagger-Johnson, G. (2012). Fuel of the self-starter: how mood relates to proactive goal regulation. J. Appl. Psychol. 97, 134–150. doi: 10.1037/a0024368

Bowers, R. I., Place, S. S., Todd, P. M., Penke, L., and Asendorpf, J. B. (2012). Generalization in mate-choice copying in humans. Behav. Ecol. 23, 112–124. doi: 10.1093/beheco/arr164

Bowlby, J. (1969). Attachment and Loss: Attachment , Vol. 1. New York, NY: Basic Books.

Bowlby, J. (1973). Attachment and Loss: Separation: Anxiety and Anger. New York, NY: Basic Books.

Bowlby, J. (1980). Attachment and Loss: Loss , Vol. 3. New York, NY: Basic Books.

Brand, S., Foell, S., Bajoghli, H., Keshavarzi, Z., Kalak, N., Gerber, M., et al. (2015). “Tell me, how bright your hypomania is, and I tell you, if you are happily in love!”-among younlove!”-among young adults in love, bright side hypomania is related to reduced depression and anxiety, and better sleep quality. Int. J. Psychiatry Clin. Pract. 19, 24–31. doi: 10.3109/13651501.2014.968588

Brand, S., Luethi, M., von Planta, A., Hatzinger, M., and Holsboer-Trachsler, E. (2007). Romantic love, hypomania, and sleep pattern in adolescents. J. Adoles. Health 41, 69–76. doi: 10.1016/j.jadohealth.2007.01.012

Bribiescas, R. G., Ellison, P. T., and Gray, P. B. (2012). Male life history, reproductive effort, and the evolution of the genus homo new directions and perspectives. Curr. Anthropol. 53, S424–S435. doi: 10.1086/667538

Bringle, R. G., Winnick, T., and Rydell, R. J. (2013). The prevalence and nature of unrequited love. SAGE Open 3:2158244013492160. doi: 10.1177/2158244013492160

Broad, K. D., Curley, J. P., and Keverne, E. B. (2006). Mother-infant bonding and the evolution of mammalian social relationships. Philos. Trans. R. Soc. B Biol. Sci. 361, 2199–2214. doi: 10.1098/rstb.2006.1940

Burton-Chellew, M. N., and Dunbar, R. I. M. (2015). Romance and reproduction are socially costly. Evol. Behav. Sci. 9, 229–241. doi: 10.1037/ebs0000046

Buss, D. M. (1988). The evolution of human intrasexual competition - tactics of mate attraction. J. Pers. Soc. Psychol. 54, 616–628. doi: 10.1037/0022-3514.54.4.616

Buss, D. M. (1989). Sex-differences in human mate preferences - evolutionary hypothesis tested in 37 cultures. Behav. Brain Sci. 12, 1–14. doi: 10.1017/s0140525x00023992

Buss, D. M. (2000). The Dangerous Passion: Why Jealousy is as Necessary as Love and Sex. New York, NY: The Free Press.

Buss, D. M. (2006). Strategies of human mating. Psychol. Top. 15, 239–260.

Buss, D. M. (2016). The Evolution of Desire: Strategies of Human Mating (Revised and updated ed.). New York, NY: Basic Books.

Buss, D. M. (2019). “The evolution of love in humans,” in The New Psychology of Love , 2nd Edn, eds R. J. Sternberg and K. Sternberg (Cambridge: Cambridge University Press).

Buss, D. M., Abbott, M., Angleitner, A., Asherian, A., Biaggio, A., Blancovillasenor, A., et al. (1990). Internaitonal preferences in selecting mates - a study of 37 cultures. J. Cross Cult. Psychol. 21, 5–47. doi: 10.1177/0022022190211001

Buss, D. M., and Barnes, M. (1986). Preferences in mate selection. J. Pers. Soc. Psychol. 50, 559–570. doi: 10.1037/0022-3514.50.3.559

Buss, D. M., Durkee, P. K., Shackelford, T. K., Bowdle, B. F., Schmitt, D. P., Brase, G. L., et al. (2020). Human status criteria: sex differences and similaritis across 14 nations. J. Pers. Soc. Psychol. 119, 979–998. doi: 10.1037/pspa0000206

Buss, D. M., Haselton, M. G., Shackelford, T. K., Bleske, A. L., and Wakefield, J. C. (1998). Adaptations, exaptations, and spandrels. Am. Psychol. 53, 533–548. doi: 10.1037/0003-066x.53.5.533

Buss, D. M., and Schmitt, D. P. (1993). Sexual strategies theory - an evolutionary perspective on human mating. Psychol. Rev. 100, 204–232. doi: 10.1037/0033-295x.100.2.204

Buss, D. M., and Schmitt, D. P. (2019). Mate preferences and their behavioral manifestations. Annu. Rev. Psychol. 70, 77–110.

Buss, D. M., Shackelford, T. K., and McKibbin, W. F. (2008). The mate retention inventory-short form (MRI-SF). Pers. Indiv. Differ. 44, 322–334. doi: 10.1016/j.paid.2007.08.013

Cacioppo, S. (2019). “Neuroimaging of love in the twenty-first crentury,” in The New Psychology of Love , 2nd Edn, eds R. J. Sternberg and K. Sternberg (Cambridge: Cambridge University Press), 64–83.

Cacioppo, S., Bianchi-Demicheli, F., Frum, C., Pfaus, J. G., and Lewis, J. W. (2012a). The common neural bases between sexual desire and love: a multilevel kernel density fMRI analysis. J. Sex. Med. 9, 1048–1054. doi: 10.1111/j.1743-6109.2012.02651.x

Cacioppo, S., Bianchi-Demicheli, F., Hatfield, E., and Rapson, R. L. (2012b). Social neuroscience of love. Clin. Neuropsychiatry 9, 3–13.

Calabrò, R. S., Cacciola, A., Bruschetta, D., Milardi, D., Quattrini, F., Sciarrone, F., et al. (2019). Neuroanatomy and function of human sexual behavior: a neglected or unknown issue? Brain Behav. 9:e01389. doi: 10.1002/brb3.1389

Calisi, R. M., and Saldanha, C. J. (2015). Neurohormones, brain, and behavior: a comparative approach to understanding rapid neuroendocrine action. Integr. Comp. Biol. 55, 264–267. doi: 10.1093/icb/icv007

Call, V., Sprecher, S., and Schwartz, P. (1995). The incidence and frequency of marital sex in a national sample. J. Marr. Fam. 57, 639–652. doi: 10.2307/353919

Cannas Aghedu, F., Veneziani, C. A., Manari, T., Feybesse, C., and Bisiacchi, P. S. (2018). Assessing passionate love: Italian validation of the PLS (reduced version). Sex. Relationsh. Ther. 35, 77–88. doi: 10.1080/14681994.2018.1442570

Carter, C. S., and Perkeybile, A. M. (2018). The monogamy paradox: what do love and sex have to do with it? Front. Ecol. Evol. 6:202. doi: 10.3389/fevo.2018.00202

Chapais, B. (2008). Primeval Kinship: How Pair-Bonding Gave Birth to Human Society. Cambridge, MA: Harvard University Press.

Chapais, B. (2013). Monogamy, strongly bonded groups, and the evolution of human social structure. Evol. Anthropol. Issues News Rev. 22, 52–65. doi: 10.1002/evan.21345

Chappel, S. C., and Howles, C. (1991). REVIEW: reevaluation of the roles of luteinizing hormone and follicle-stimulating hormone in the ovulatory process. Hum. Reprod. 6, 1206–1212. doi: 10.1093/oxfordjournals.humrep.a137513

Conroy-Beam, D., and Buss, D. M. (2016). How are mate preferences linked with actual mate selection? Tests of mate preference integration algorithms using computer simulations and actual mating couples. PLos One 11:e0156078. doi: 10.1371/journal.pone.0156078

Conroy-Beam, D., Goetz, C. D., and Buss, D. M. (2015). “Chapter One - Why do humans form long-term mateships? An evolutionary game-theoretic model,” in Advances in Experimental Social Psychology , eds J. M. Olson and M. P. Zanna (Cambridge, MA: Academic Press), 1–39.

Conroy-Beam, D., Goetz, C. D., and Buss, D. M. (2016). What predicts romantic relationship satisfaction and mate retention intensity: mate preference fulfillment or mate value discrepancies? Evol. Hum. Behav. 37, 440–448. doi: 10.1016/j.evolhumbehav.2016.04.003

Curley, J. P., and Keverne, E. B. (2005). Genes, brains and mammalian social bonds. Trends Ecol. Evol. 20, 561–567. doi: 10.1016/j.tree.2005.05.018

D’Acquisto, F. (2017). Affective immunology: where emotions and the immune response converge. Dialog. Clin Neurosci 19, 9–19.

Darwin, C. (1859). On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. London: John Murray.

Darwin, C. (2013). The Descent of Man and Selection in Relation to Sex. Cambridge: Cambridge University Press.

Dawkins, R. (1982). The Extended Phenotype: The Gene as the Unit of Selection. Oxford, UK: Oxford University Press.

Dawson, L. H., Shih, M. C., de Moor, C., and Shrier, L. (2008). Reasons why adolescents and young adults have sex: associations with psychological characteristics and sexual behavior. J. Sex Res. 45, 225–232. doi: 10.1080/00224490801987457

de Boer, A., van Buel, E. M., and Ter Horst, G. J. (2012). Love is more than just a kiss: a neurobiological perspective on love and affection. Neuroscience 201, 114–124. doi: 10.1016/j.neuroscience.2011.11.017

de Munck, V. C., and Korotayev, A. (1999). Sexual equality and romantic love: a reanalysis of Rosenblatt’s study on the function of romantic love. Cross Cult. Res. 33, 265–277. doi: 10.1177/106939719903300303

Dean, J., and Keshavan, M. (2017). The neurobiology of depression: an integrated view. Asian J. Psychiatry 27, 101–111. doi: 10.1016/j.ajp.2017.01.025

Del Giudice, M. (2016). The life history model of psychopathology explains the structure of psychiatric disorders and the emergence of the p factor: a simulation study. Clin. Psychol. Sci. 4, 299–311. doi: 10.1177/2167702615583628

DePaulo, B. M., and Morris, W. L. (2006). The unrecognized stereotyping and discrimination against singles. Curr. Direct. Psychol. Sci. 15, 251–254. doi: 10.1111/j.1467-8721.2006.00446.x

Diamond, L. M. (2004). Emerging perspectives on distinctions between romantic love and sexual desire. Curr. Direct. Psychol. Sci. 13, 116–119. doi: 10.1111/j.0963-7214.2004.00287.x

Diamond, L. M., and Dickenson, J. A. (2012). The neuroimaging of love and desire: review and future directions. Clin. Neuropsychiatry J. Treat. Eval. 9, 39–46.

Dixson, A. (2009). Sexual Selection and the Origins of Human Mating Systems. Oxford: Oxford University Press.

Dunbar, R. I. M. (2012). The Science of Love and Betrayal. London: Faber and Faber.

Dundon, C. M., and Rellini, A. H. (2012). Emotional states of love moderate the association between catecholamines and female sexual responses in the laboratory. J. Sex. Med. 9, 2617–2630. doi: 10.1111/j.1743-6109.2012.02799.x

Durdiakova, J. B., Celec, P., Koborova, I., Sedlackova, T., Minarik, G., and Ostatnikova, D. (2017). How do we love? Romantic love style in men is related to lower testosterone levels. Physiol. Res. 66, 695–703. doi: 10.33549/physiolres.933523

Durisko, Z., Mulsant, B. H., McKenzie, K., and Andrews, P. W. (2016). Using evolutionary theory to guide mental health research. Can. J. Psychiatry 61, 159–165. doi: 10.1177/0706743716632517

Dutra, S. J., Cunningham, W. A., Kober, H., and Gruber, J. (2015). Elevated striatal reactivity across monetary and social rewards in bipolar I disorder. J. Abnorm. Psychol. 124, 890–904. doi: 10.1037/abn0000092

Edward, D. A. (2015). The description of mate choice. Behav. Ecol. 26, 301–310. doi: 10.1093/beheco/aru142

Emanuele, E., Brondino, N., Pesent, S., Re, S., and Geroldi, D. (2007). Genetic loading on human loving styles. Neuroendocrinol. Lett. 28, 815–821.

Emanuele, E., Politi, P., Bianchi, M., Minoretti, P., Bertona, M., and Geroldi, D. (2006). Raised plasma nerve growth factor levels associated with early-stage romantic love. Psychoneuroendocrinology 31, 288–294. doi: 10.1016/j.psyneuen.2005.09.002

Esch, T., and Stefano, G. B. (2005). Love promotes health. Neuroendocrinol. Lett. 26, 264–267.

Feybesse, C., and Hatfield, E. (2019). “Passionate love,” in The New Psychology of Love , 2nd Edn, eds R. J. Sternberg and K. Sternberg (Cambridge: Cambridge University Press).

Figueredo, A. J., Vásquez, G., Brumbach, B. H., and Schneider, S. M. (2004). The heritability of life history strategy: the k-factor, covitality, and personality. Soc. Biol. 51, 121–143. doi: 10.1080/19485565.2004.9989090

Fischer, E. K., Nowicki, J. P., and O’Connell, L. A. (2019). Evolution of affiliation: patterns of convergence from genomes to behaviour. Philos. Trans. R. Soc. B Biol. Sci. 374:20180242. doi: 10.1098/rstb.2018.0242

Fisher, H. (1995). “The nature and evolution of romantic love,” in Romantic Passion: A Universal Experience , ed. W. R. Jankowiak (New York, NY: Columbia University Press), 23–41.

Fisher, H. (2000). Lust, attraction, attachment: biology and evolution of the three primary emotion systems for mating, reproduction, and parenting. J. Sex Educ. Ther. 25, 96–104. doi: 10.1080/01614576.2000.11074334

Fisher, H. (2006). “The drive to love: the neural mechanism for mate selection,” in The New Psychology of Love , eds R. J. Sternberg and K. Weis (New Haven, CT: Yale Unviersity Press), 87–115.

Fisher, H. (2011). Why Him? Why Her?: How to Find and Keep Lasting Love , 2nd Edn. London: Oneworld.

Fisher, H. E. (1998). Lust, attraction, and attachment in mammalian reproduction. Hum. Nat. Interdiscipl. Biosoc. Perspect. 9, 23–52. doi: 10.1007/s12110-998-1010-5

Fisher, H. E. (2004). Why We Love: The Nature and Chemistry of Romantic Love. New York, NY: St Martin’s Griffin.

Fisher, H. E. (2016). Anatomy of Love: A natural History of Mating, Marriage, and Why We Stray. New York, NY: W. W. Norton & Company.

Fisher, H., Aron, A., and Brown, L. L. (2005). Romantic love: an fMRI study of a neural mechanism for mate choice. J. Comp. Neurol. 493, 58–62. doi: 10.1002/cne.20772

Fisher, H. E., Aron, A., Brown, L. L. (2006). Romantic love: a mammalian brain system for mate choice. Philos. Trans. R. Soc. B Biol. Sci. 361, 2173–2186. doi: 10.1098/rstb.2006.1938

Fisher, H. E., Aron, A., Mashek, D., Li, H., and Brown, L. L. (2002). Defining the brain systems of lust, romantic attraction, and attachment. Arch. Sex. Behav. 31, 413–419. doi: 10.1023/a:1019888024255

Fisher, H. E., Brown, L. L., Aron, A., Strong, G., and Mashek, D. (2010). Reward, addiction, and emotion regulation systems associated with rejection in love. J. Neurophysiol. 104, 51–60. doi: 10.1152/jn.00784.2009

Fisher, H. E., Xu, X. M., Aron, A., and Brown, L. L. (2016). Intense, passionate, romantic love: a natural addiction? How the fields that investigate romance and substance abuse can inform each other. Front. Psychol. 7:687. doi: 10.3389/fpsyg.2016.00687

Flajnik, M. F., and Kasahara, M. (2010). Origin and evolution of the adaptive immune system: genetic events and selective pressures. Nat. Rev. Genet. 11, 47–59. doi: 10.1038/nrg2703

Fletcher, G. J. O., Simpson, J. A., Campbell, L., and Overall, N. C. (2015). Pair-bonding, romantic love, and evolution: the curious case of Homo sapiens . Perspect. Psychol. Sci. 10, 20–36. doi: 10.1177/1745691614561683

Fox, C. W., and Westneat, D. F. (2010). “Adaptation,” in Evolutionary Behavioural Ecology , eds D. F. Westneat and C. W. Fox (New York, NY: Oxford University Press), 16–31.

Frank, R. H. (1988). Passion Within Reason: The Strategic Role of the Emotions. New York, NY: Norton.

French, J. A., Cavanaugh, J., Mustoe, A. C., Carp, S. B., and Womack, S. L. (2018). Social monogamy in nonhuman primates: phylogeny, phenotype, and physiology. J. Sex Res. 55, 410–434. doi: 10.1080/00224499.2017.1339774

Garcia, C. Y. (1997). Temporal course of basic components of love along the couple relationship. Psicothema 9, 1–15.

Garrett, A., and Chang, K. (2008). The role of the amygdala in bipolar disorder development. Dev. Psychopathol. 20, 1285–1296. doi: 10.1017/s0954579408000618

Gavrilets, S. (2012). Human origins and the transition from promiscuity to pair-bonding. Proc. Natl. Acad. Sci. U.S.A. 109, 9923–9928. doi: 10.1073/pnas.1200717109

Geary, D. C., Vigil, J., and Byrd-Craven, J. (2004). Evolution of human mate choice. J. Sex Res. 41, 27–42. doi: 10.1080/00224490409552211

Gleeson, B. T., and Kushnick, G. (2018). Female status, food security, and stature sexual dimorphism: testing mate choice as a mechanism in human self-domestication. Am. J. Phys. Anthropol. 167, 458–469. doi: 10.1002/ajpa.23642

Goetz, C. D., Pillsworth, E. G., Buss, D. M., and Conroy-Beam, D. (2019). Evolutionary mismatch in mating. Front. Psychol. 10:2709. doi: 10.3389/fpsyg.2019.02709

Goldenberg, R. L., and McClure, E. M. (2011). Maternal mortality. Am. J. Obstetr. Gynecol. 205, 293–295. doi: 10.1016/j.ajog.2011.07.045

Gottschall, J., and Nordlund, M. (2006). Romantic love: a literary universal? Philos. Liter. 30, 450–470. doi: 10.1353/phl.2006.0030

Graham, J. M. (2011). Measuring love in romantic relationships: a meta-analysis. J. Soc. Pers. Relationsh. 28, 748–771. doi: 10.1177/0265407510389126

Griskevicius, V., Tybur, J. M., Sundie, J. M., Cialdini, R. B., Miller, G. F., and Kenrick, D. T. (2007). Blatant benevolence and conspicuous consumption: when romantic motives elicit strategic costly signals. J. Pers. Soc. Psychol. 93, 85–102. doi: 10.1037/0022-3514.93.1.85

Hatfield, E., Bensman, L., and Rapson, R. L. (2012). A brief history of social scientists’ attempts to measure passionate love. J. Soc. Pers. Relationsh. 29, 143–164. doi: 10.1177/0265407511431055

Hatfield, E., Brinton, C., and Cornelius, J. (1989). Passioante love and anxiety in young adolescents. Motiv. Emot. 13, 271–289. doi: 10.1007/bf00995539

Hatfield, E., Feybesse, C., Narine, V., and Rapson, R. L. (2016). “Passionate love: inspired by angels or demons?,” in The Psychology of Love and Hate in Intimate Relatinships , ed. K. Aumer (New York, NY: Springer).

Hatfield, E., and Rapson, R. L. (1993). Love, Sex, and Intimacy: Their Psychology, Biology, and History. New York, NY: HarperCollins College Publishers.

Hatfield, E., and Rapson, R. L. (2009). “The neuropsychology of passionate love and sexual desire,” in Psychology of Social Relationships , eds E. Cuyler and M. Ackhart (Hauppauge, NY: Nova Science).

Hatfield, E., Schmitz, E., Cornelius, J., and Rapson, R. L. (1988). Passionate love: how early does it begin? J. Psychol. Hum. Sex. 1, 35–51. doi: 10.1300/J056v01n01_04

Hatfield, E., and Sprecher, S. (1986). Measuring passionate love in intimate relationships. J. Adolesc. 9, 383–410. doi: 10.1016/S0140-1971(86)80043-4

Hatfield, E., and Sprecher, S. (2011). “The passionate love scale,” in Handbook of Sexuality-Related Measures: A Compendium , 3rd Edn, eds T. D. Fisher, C. M. Davis, W. L. Yaber, and S. L. Davis (Thousand Oaks, CA: Taylor & Francis).

Hatfield, E., Traupmann, J. P., O’Brien, M. U., and Le, Y.-C. L. (2008). The endurance of love: passionate and companionate love in newlywed and long-term marriages. Interpers. Int. J. Pers. Relationsh. 2, 35–64. doi: 10.5964/ijpr.v2i1.17

Hatfield, E., and Walster, G. W. (1985). A New Look at Love. Lanham, MD: University Press of America.

Hazan, C., and Diamond, L. (2000). The place of attachment in human mating. Rev. Gen. Psychol. 4, 186–204. doi: 10.1037/1089-2680.4.2.186

Hazan, C., and Shaver, P. (1987). Romantic love conceptualized as an attachment process. J. Pers. Soc. Psychol. 52, 511–524. doi: 10.1037/0022-3514.52.3.511

Hendrick, C., and Hendrick, S. (1986). A theory and method of love. J. Pers. Soc. Psychol. 50, 392–402. doi: 10.1037/0022-3514.50.2.392

Hendrick, C., and Hendrick, S. S. (1989). Research on love - does it measure up. J. Pers. Soc. Psychol. 56, 784–794. doi: 10.1037/0022-3514.56.5.784

Hendrick, C., and Hendrick, S. S. (1991). Dimensions of love - a sociobiological interpretation. J. Soc. Clin. Psychol. 10, 206–230. doi: 10.1521/jscp.1991.10.2.206

Hendrick, C., and Hendrick, S. S. (2019). “Styles of romantic love,” in The New Pscyhology of Love , 2nd Edn, eds R. J. Sternberg and K. Sternberg (Cambridge: Cambridge University Press).

Hendrick, C., Hendrick, S. S., and Dicke, A. (1998). The love attitudes scale: short form. J. Soc. Pers. Relationsh. 15, 147–159. doi: 10.1177/0265407598152001

Hendrick, S. S., and Hendrick, C. (1995). Gender differences and similarities in sex and love. Pers. Relationsh. 2, 55–65. doi: 10.1111/j.1475-6811.1995.tb00077.x

Henrich, J., Heine, S. J., and Norenzayan, A. (2010). The weirdest people in the world? Behav. Brain Sci. 33, 61–83. doi: 10.1017/s0140525x0999152x

Hill, C. A., Blakemore, J. E. O., and Drumm, P. (1997). Mutual and unrequited love in adolescence and young adulthood. Pers. Relationsh. 4, 15–23. doi: 10.1111/j.1475-6811.1997.tb00127.x

Holloway, V., and Wylie, K. (2015). Sex drive and sexual desire. Curr. Opin. Psychiatry 28, 424–429. doi: 10.1097/yco.0000000000000199

IsHak, W. W., Kahloon, M., and Fakhry, H. (2011). Oxytocin role in enhancing well-being: a literature review. J. Affect. Disord. 130, 1–9. doi: 10.1016/j.jad.2010.06.001

Jahangard, L., Rahmani, A., Haghighi, M., Ahmadpanah, M., Sadeghi Bahmani, D., Soltanian, A. R., et al. (2017). “Always look on the bright side of life!” – Higher hypomania scores are associated with higher mental toughness, increased physical activity, and lower symptoms of depression and lower sleep complaints. Front. Psychol. 8:2130. doi: 10.3389/fpsyg.2017.02130

Jankowiak, W. R. (ed.) (1995). Romantic Passion: A Universal Experience?. New York, NY: Columbia University Press.

Jankowiak, W. R. (ed.) (2008). Intimacies: Love and Sex Across Cultures. New York, NY: Columbia University Press.

Jankowiak, W. R., and Fischer, E. F. (1992). A cross-cultural perspective on romantic love. Ethnology 31, 149–155. doi: 10.2307/3773618

Jankowiak, W. R., and Paladino, T. (2008). “Desiring sex, longing for love: a tripartite continuum,” in Intimacies: Love and Sex Across Cultures , ed. W. R. Jankowiak (New York: Columbia University Press), 1–36.

Jonsson, E. G., Nothen, M. M., Grunhage, F., Farde, L., Nakashima, Y., Propping, P., et al. (1999). Polymorphisms in the dopamine D2 receptor gene and their relationships to striatal dopamine receptor density of healthy volunteers. Mol. Psychiatry 4, 290–296. doi: 10.1038/sj.mp.4000532

Johnson, Z. V., and Young, L. J. (2015). Neurobiological mechanisms of social attachment and pair bonding. Curr. Opin. Behav. Sci. 3, 38–44. doi: 10.1016/j.cobeha.2015.01.009

Johnstone, R. A., and Earn, D. J. D. (1999). Imperfect female choice and male mating skew on leks of different sizes. Behav. Ecol. Sociobiol. 45, 277–281. doi: 10.1007/s002650050562

Jones, A. G., and Ratterman, N. L. (2009). Mate choice and sexual selection: what have we learned since Darwin? Proc. Natl. Acad. Sci. U.S.A. 106, (Suppl. 1), 10001–10008. doi: 10.1073/pnas.0901129106

Jørgensen, T. N., Christensen, P. M., and Gether, U. (2014). Serotonin-induced down-regulation of cell surface serotonin transporter. Neurochem. Int. 73, 107–112. doi: 10.1016/j.neuint.2014.01.005

Kay, R. F., Ross, C., and Williams, B. A. (1997). Anthropoid origins. Science 275, 797. Science 275, 797. doi: 10.1126/science.275.5301.797

Kenrick, D. T. (2006). “A dynamical evolutionary view of love,” in The New Psychology of Love , eds R. J. Sternberg and K. Weis (New Haven, CT: Yale University Press).

Kenrick, D. T., Sadalla, E. K., Groth, G., and Trost, M. R. (1990). Evolution, traits, and the stages of human courship - qualifying the parental investment model. J. Pers. 58, 97–116. doi: 10.1111/j.1467-6494.1990.tb00909.x

Klug, H. (2018). Why monogamy? A review of potential ultimate drivers. Front. Ecol. Evol. 6:30. doi: 10.3389/fevo.2018.00030

Koehn, M. A., and Jonason, P. K. (2018). “Costs of short-term mating for women,” in Encyclopedia of Evolutionary Psychological Science , eds T. K. Shackelford and V. A. Weekes-Shackelford (Cham: Springer International Publishing), 1–6.

Koob, G. F., and Volkow, N. D. (2016). Neurobiology of addiction: a neurocircuitry analysis. Lancet Psychiatry 3, 760–773. doi: 10.1016/S2215-0366(16)00104-8

Kushnick, G. (2016). “Ecology of pairbond stability,” in Encyclopedia of Evolutionary Psychological Science , eds T. Shackelford and V. Weekes-Shackelford (New York, NY: Springer), 1–7.

Kushnick, G. (2019). The cradle of humankind: evolutionary approaches to technology and parenting. SocArXiv doi: 10.31235/osf.io/k23md

Kuula, L., Partonen, T., and Pesonen, A. K. (2020). Emotions relating to romantic love-further disruptors of adolescent sleep. Sleep Health 6, 159–165. doi: 10.1016/j.sleh.2020.01.006

Laland, K. N., and Brown, G. R. (2011). Sense and Nonsense: Evolutionary Perspectives on Human Behaviour , 2nd Edn. Oxford: Oxford University Press.

Langeslag, S. J. E., van der Veen, F. M., and Fekkes, D. (2012). Blood levels of serotonin are differentially affected by romantic love in men and women. J. Psychophysiol. 26, 92–98. doi: 10.1027/0269-8803/a000071

Leckman, J. F., and Mayes, L. C. (1999). Preoccupations and behaviors associated with romantic and parental love - Perspectives on the origin of obsessive-compulsive disorder. Child Adoles. Psychiatr. Clin. N. Am. 8, 635–665.

Lee, J. (1976). The Colours of Love. Englewood Cliffs, NJ: Prentice-Hall.

Li, N. P., Bailey, J. M., Kenrick, D. T., and Linsenmeier, J. A. W. (2002). The necessities and luxuries of mate preferences: testing the tradeoffs. J. Pers. Soc. Psychol. 82, 947–955. doi: 10.1037//0022-3514.82.6.947

Li, N. P., and Meltzer, A. L. (2015). The validity of sex-differentiated mate preferences: reconciling the seemingly conflicting evidence. Evol. Behav. Sci. 9, 89–106. doi: 10.1037/ebs0000036

Li, N. P., van Vugt, M., and Colarelli, S. M. (2018). The evolutionary mismatch hypothesis: implications for psychological science. Curr. Direct. Psychol. Sci. 27, 38–44. doi: 10.1177/0963721417731378

Li, N. P., Yong, J. C., Tov, W., Sng, O., Fletcher, G. J. O., Valentine, K. A., et al. (2013). Mate preferences do predict attraction and choices in the early stages of mate selection. J. Pers. Soc. Psychol. 105, 757–776. doi: 10.1037/a0033777

Lieberman, D., and Hatfield, E. (2006). “Passionate love: cross-cultural and evolutionary perspectives,” in The New Psychology of Love , (New Haven, CT: Yale University Press), 274–297.

Liu, X., Zhang, T., He, S., Hong, B., Peng, D., Su, H., et al. (2014). Nerve growth factor variations in patients with mood disorders: no changes in eight weeks of clinical treatment. Neuropsychiatr. Dis. Treat. 10, 835–840. doi: 10.2147/NDT.S62741

Loonen, A. J. M., and Ivanova, S. A. (2015). Circuits regulating pleasure and happiness: the evolution of reward-seeking and misery-fleeing behavioral mechanisms in vertebrates. Front. Neurosci. 9:394. doi: 10.3389/fnins.2015.00394

Loth, M. K., and Donaldson, Z. R. (2021). Oxytocin, dopamine, and opioid interactions underlying pair bonding: highlighting a potential role for microglia. Endocrinol. 162:bqaa223. doi: 10.1210/endocr/bqaa223

Lovejoy, C. O. (1981). The origin of man. Science 211, 341–350. doi: 10.1126/science.211.4480.341

Lukas, D., and Clutton-Brock, T. H. (2013). The evolution of social monogamy in mammals. Science 341:526. doi: 10.1126/science.1238677

Luoto, S. (2019a). An updated theoretical framework for human sexual selection: from ecology, genetics, and life history to extended phenotypes. Adapt. Hum. Behav. Physiol. 5, 48–102. doi: 10.1007/s40750-018-0103-6

Luoto, S. (2019b). Response to commentaries: life history genetics, fluid intelligence, and extended phenotypes. Adapt. Hum. Behav. Physiol. 5, 112–115. doi: 10.1007/s40750-019-0109-8

Luoto, S. (2020). Did prosociality drive the evolution of homosexuality? Arch. Sex. Behav . 49, 2239–2244. doi: 10.1007/s10508-020-01749-0

Luoto, S., Krams, I., and Rantala, M. J. (2019). A life history approach to the female sexual orientation spectrum: evolution, development, causal mechanisms, and health. Arch. Sex. Behav. 48, 1273–1308. doi: 10.1007/s10508-018-1261-0

Luttbeg, B. (2002). Assessing the robustness and optimality of alternative decision rules with varying assumptions. Anim. Behav. 63, 805–814. doi: 10.1006/anbe.2001.1979

Maletic, V., and Raison, C. (2014). Integrated neurobiology of bipolar disorder. Front. Psychiatry 5:98. doi: 10.3389/fpsyt.2014.00098

Manji, H. K., Quiroz, J. A., Payne, J. L., Singh, J., Lopes, B. P., Viegas, J. S., et al. (2003). The underlying neurobiology of bipolar disorder. World Psychiatry 2, 136–146.

Marazziti, D., Akiskal, H. S., Rossi, A., and Cassano, G. B. (1999). Alteration of the platelet serotonin transporter in romantic love. Psychol. Med. 29, 741–745. doi: 10.1017/s0033291798007946

Marazziti, D., Baroni, S., Giannaccini, G., Piccinni, A., Mucci, F., Catena-Dell’Osso, M., et al. (2017). Decreased lymphocyte dopamine transporter in romantic lovers. CNS Spectrums 22, 290–294. doi: 10.1017/s109285291600050x

Marazziti, D., and Canale, D. (2004). Hormonal changes when falling in love. Psychoneuroendocrinology 29, 931–936. doi: 10.1016/j.psyneuen.2003.08.006

Marazziti, D., Falaschi, V., Lombardi, A., Mungai, F., and Dell’osso, L. (2015). Stalking: a neurobiological perspective. Riv. Psichiatr. 50, 12–18. Retrieved from <Go to ISI>://WOS:000350408600004

Marlowe, F. W. (2003). A critical period for provisioning by Hadza men: implications for pair bonding. Evol. Hum. Behav. 24, 217–229. doi: 10.1016/s1090-5138(03)00014-x

Martin, E. I., Ressler, K. J., Binder, E., and Nemeroff, C. B. (2009). The neurobiology of anxiety disorders: brain imaging, genetics, and psychoneuroendocrinology. Psychiatr. Clin. North Am. 32, 549–575. doi: 10.1016/j.psc.2009.05.004

Marzec, M., and Łukasik, A. (2017). Love styles in the context of life history theory. Polish Psychol. Bull. 48, 237–249. doi: 10.1515/ppb-2017-0027

Masuda, M. (2003). Meta-analyses of love scales: do various love scales measure the same psychological constructs? Jpn. Psychol. Res. 45, 25–37. doi: 10.1111/1468-5884.00030

Mayr, E. (1961). Cause and effect in biology - kinds of causes, predictability, and teleology are viewed by a practicing biologist. Science 134, 1501–1506. doi: 10.1126/science.134.3489.1501

McCarthy, M. M. (2020). A new view of sexual differentiation of mammalian brain. J. Comp. Physiol. Neuroethol. Sens. Neural Behav. Physiol. 206, 369–378. doi: 10.1007/s00359-019-01376-8

McLennan, D. A. (2008). The concept of co-option: why evolution often looks miraculous. Evol. Educ. Outreach 1, 247–258. doi: 10.1007/s12052-008-0053-8

McQuaid, R. J., McInnis, O. A., Abizaid, A., and Anisman, H. (2014). Making room for oxytocin in understanding depression. Neurosci. Biobehav. Rev. 45, 305–322. doi: 10.1016/j.neubiorev.2014.07.005

Meltzer, A. L., Makhanova, A., Hicks, L. L., French, J. E., McNulty, J. K., and Bradbury, T. N. (2017). Quantifying the sexual afterglow: the lingering benefits of sex and their implications for pair-bonded relationships. Psychol. Sci. 28, 587–598. doi: 10.1177/0956797617691361

Mercado, C. P., and Kilic, F. (2010). Molecular mechanisms of SERT in platelets: regulation of plasma serotonin levels. Mol. Intervent. 10, 231–241. doi: 10.1124/mi.10.4.6

Mercado, E., and Hibel, L. C. (2017). I love you from the bottom of my hypothalamus: the role of stress physiology in romantic pair bond formation and maintenance. Soc. Pers. Psychol. Compass 11:e12298. doi: 10.1111/spc3.12298

Meston, C. M., and Buss, D. M. (2007). Why humans have sex. Arch. Sex. Behav. 36, 477–507. doi: 10.1007/s10508-007-9175-2

Meston, C. M., and Buss, D. M. (2009). Why Women Have Sex. New York, NY: St Martin’s Griffin.

Miller, G. F., and Todd, P. M. (1998). Mate choice turns cognitive. Trends Cogn. Sci. 2, 190–198. doi: 10.1016/s1364-6613(98)01169-3

Mohammad-Zadeh, L. F., Moses, L., and Gwaltney-Brant, S. M. (2008). Serotonin: a review. J. Vet. Pharmacol. Therapeut. 31, 187–199. doi: 10.1111/j.1365-2885.2008.00944.x

Mooradian, A. D., Morley, J. E., and Korenman, S. G. (1987). Biological actions of androgens. Endocr. Rev. 8, 1–28. doi: 10.1210/edrv-8-1-1

Morin, P. A. (1993). Reproductive strategies in chimpanzees. Am. J. Phys. Anthropol. 36, 179–212. doi: 10.1002/ajpa.1330360610

Morris, W. N. (2003). “The mood system,” in Well-Being: Foundations of Hedonic Psychology , eds D. Kahneman, E. Diener, and N. Schwarz (New York, NY: Russell Sage Foundation), 169–189.

Motta-Mena, N. V., and Puts, D. A. (2017). Endocrinology of human female sexuality, mating, and reproductive behavior. Hormon. Behav. 91, 19–35. doi: 10.1016/j.yhbeh.2016.11.012

Murray, D. R., Haselton, M. G., Fales, M., and Cole, S. W. (2019). Falling in love is associated with immune system gene regulation. Psychoneuroendocrinology 100, 120–126. doi: 10.1016/j.psyneuen.2018.09.043

Nesse, R. (2019). Good Reasons for Bad Feelings: Insights Form the Frontier of Evolutionary Psychiatry. Great Britain, UK: Allen Lane.

Nesse, R. M. (2013). Tinbergen’s four questions, organized: a response to Bateson and Laland. Trends Ecol. Evol. 28, 681–682. doi: 10.1016/j.tree.2013.10.008

Nettle, D., and Bateson, M. (2012). The evolutionary origins of mood and its disorders. Curr. Biol. 22, R712–R721. doi: 10.1016/j.cub.2012.06.020

Neumann, I. D., and Landgraf, R. (2012). Balance of brain oxytocin and vasopressin: implications for anxiety, depression, and social behaviors. Trends Neurosci. 35, 649–659. doi: 10.1016/j.tins.2012.08.004

Numan, M., and Young, L. J. (2016). Neural mechanisms of mother-infant bonding and pair bonding: similarities, differences, and broader implications. Hormon. Behav. 77, 98–112. doi: 10.1016/j.yhbeh.2015.05.015

Oesch, N., and Miklousic, I. (2012). The dating mind: evolutionary psychology and the emerging science of human courtship. Evol. Psychol. 10:147470491201000511. doi: 10.1177/147470491201000511

Olderbak, S., and Figueredo, A. J. (2009). Predicting romantic relationship satisfaction from life history strategy. Pers. Indiv. Differ. 46, 604–610. doi: 10.1016/j.paid.2008.12.019

O’Leary, K. D., Acevedo, B. P., Aron, A., Huddy, L., and Mashek, D. (2011). Is long-term love more than a rare phenomenon? If so, what are its correlates? Soc. Psychol. Pers. Sci. 3, 241–249. doi: 10.1177/1948550611417015

Opie, C., Atkinson, Q. D., Dunbar, R. I. M., and Shultz, S. (2013). Male infanticide leads to social monogamy in primates. Proc. Natl. Acad. Sci. U.S.A. 110, 13328–13332. doi: 10.1073/pnas.1307903110

Ortigue, S., Bianchi-Demicheli, F., Hamilton, A., and Grafton, S. T. (2007). The neural basis of love as a subliminal prime: an event-related functional magnetic resonance imaging study. J. Cogn. Neurosci. 19, 1218–1230. doi: 10.1162/jocn.2007.19.7.1218

Ortigue, S., Bianchi-Demicheli, F., Patel, N., Frum, C., and Lewis, J. W. (2010). Neuroimaging of love: fMRI meta-analysis evidence toward new perspectives in sexual medicine. J. Sex. Med. 7, 3541–3552. doi: 10.1111/j.1743-6109.2010.01999.x

Ozer, E. J., Dolcini, M. M., and Harper, G. W. (2003). Adolescents’ reasons for having sex: gender differences. J. Adolesc. Health 33, 317–319. doi: 10.1016/j.jadohealth.2003.06.012

Pigliucci, M., and Kaplan, J. (2006). “Testing adaptive hypotheses: historical evidence and human adaptations,” in Making Sense of Evolution: The Conceptual Foundations of Evolutionary Biology , eds M. Pigliucci and J. Kaplan (Chicago, IL: University of Chicago Press), 150–174.

Pines, A. M. (2001). The role of gender and culture in romantic attraction. Eur. Psychol. 6, 96–102. doi: 10.1027//1016-9040.6.2.96

Pines, A. M. (2005). Falling in Love: Why We Choose The Lovers We Choose , 2nd Edn. New York, NY: Routledge.

Porges, S. W. (1998). Love: an emergent property of the mammalian autonomic nervous system. Psychoneuroendocrinology 23, 837–861.

Price, M., Hides, L., Cockshaw, W., Staneva, A. A., and Stoyanov, S. R. (2016). Young love: romantic concerns and associated mental health issues among adolescent help-seekers. Behav. Sci. 6:14. doi: 10.3390/bs6020009

Purba, J. S., Hoogendijk, W. J. G., Hofman, M. A., and Swaab, D. F. (1996). Increased number of vasopressin- and oxytocin-expressing neurons in the paraventricular nucleus of the hypothalamus in depression. Arch. Gen. Psychiatry 53, 137–143.

Quinlan, R. J. (2008). Human pair-bonds: evolutionary functions, ecological variation, and adaptive development. Evol. Anthropol. 17, 227–238. doi: 10.1002/evan.20191

Rantala, M. J., Luoto, S., Krama, T., and Krams, I. (2019). Eating disorders: an evolutionary psychoneuroimmunological approach. Front. Psychol. 10:2200. doi: 10.3389/fpsyg.2019.02200

Rantala, M. J., Luoto, S., Krams, I., and Karlsson, H. (2018). Depression subtyping based on evolutionary psychiatry: proximate mechanisms and ultimate functions. Brain Behav. Immun. 69, 603–617. doi: 10.1016/j.bbi.2017.10.012

Reeve, H. K., and Sherman, P. W. (1993). Adaptation and the goals of evolutionary research. Q. Rev. Biol. 68, 1–32. doi: 10.1086/417909

Reynaud, M., Karila, L., Blecha, L., and Benyamina, A. (2010). Is love passion an addictive disorder? Am. J. Drug Alcohol Abuse 36, 261–267. doi: 10.3109/00952990.2010.495183

Riela, S., Bajoghli, H., Xu, X. M., Farnia, V., Golshani, S., and Shakeri, J. (2017). Falling in love and passionate love in an iranian sample. Interpersona 11, 141–155. doi: 10.5964/ijpr.v11i2.272

Riela, S., Rodriguez, G., Aron, A., Xu, X. M., and Acevedo, B. P. (2010). Experiences of falling in love: investigating culture, ethnicity, gender, and speed. J. Soc. Pers. Relationsh. 27, 473–493. doi: 10.1177/0265407510363508

Rosenfeld, M. J., Thomas, R. J., and Hausen, S. (2019). Disintermediating your friends: how online dating in the United States displaces other ways of meeting. Proc. Natl. Acad. Sci. U.S.A. 116, 17753–17758. doi: 10.1073/pnas.1908630116

Salska, I., Frederick, D. A., Pawlowski, B., Reilly, A. H., Laird, K. T., and Rudd, N. A. (2008). Conditional mate preferences: factors influencing preferences for height. Pers. Indiv. Differ. 44, 203–215. doi: 10.1016/j.paid.2007.08.008

Satake, A. (2018). “Flowering time as a model trait to bridge proximate and evolutionary questions,” in Mathematical Modelling in Plant Biology , ed. R. Morris (Switzerland: Springer Nature), 171–194.

Scelza, B. A., Prall, S. P., Blumenfield, T., Crittenden, A. N., Gurven, M., Kline, M., et al. (2020). Patterns of paternal investment predict cross-cultural variation in jealous response. Nat. Hum. Behav. 4, 20–26. doi: 10.1038/s41562-019-0654-y

Schacht, R., and Kramer, K. L. (2019). Are we monogamous? A review of the evolution of pair-bonding in humans and its contemporary variation cross-culturally. Front. Ecol. Evol. 7:230. doi: 10.3389/fevo.2019.00230

Scheele, D., Wille, A., Kendrick, K. M., Stoffel-Wagner, B., Becker, B., Gunturkun, O., et al. (2013). Oxytocin enhances brain reward system responses in men viewing the face of their female partner. Proc. Natl. Acad. Sci. USA 110, 20308–20313. doi: 10.1073/pnas.1314190110

Schmitt, D. P. (2006). “Evolutionary and cross-cultural perspectives on love: the influence of gender, personality, and local ecology on emotional investment in romantic relationships,” in The New Pscyhology of Love , eds R. J. Sternberg and K. Weis (New Haven, CT: Yale University Press).

Schneiderman, I., Kanat-Maymon, Y., Zagoory-Sharon, O., and Feldman, R. (2014). Mutual influences between partners’ hormones shape conflict dialog and relationship duration at the initiation of romantic love. Soc. Neurosci. 9, 337–351. doi: 10.1080/17470919.2014.893925

Schneiderman, I., Zagoory-Sharon, O., Leckman, J. F., and Feldman, R. (2012). Oxytocin during the initial stages of romantic attachment: relations to couples’ interactive reciprocity. Psychoneuroendocrinology 37, 1277–1285. doi: 10.1016/j.psyneuen.2011.12.021

Seymour, R. M., and Sozou, P. D. (2009). Duration of courtship effort as a costly signal. J. Theoret. Biol. 256, 1–13. doi: 10.1016/j.jtbi.2008.09.026

Shackelford, T. K., Buss, D. M., and Weekes-Shackelford, V. A. (2003). Wife killings committed in the context of a lovers triangle. Basic Appl. Soc. Psychol. 25, 137–143. doi: 10.1207/s15324834basp2502_4

Sheets, V. L. (2013). Passion for life: self-expansion and passionate love across the life span. J. Soc. Pers. Relationsh. 31, 958–974. doi: 10.1177/0265407513515618

Shiah, I. S., and Yatham, L. N. (2000). Serotonin in mania and in the mechanism of action of mood stabilizers: a review of clinical studies. Bipolar Disord. 2, 77–92. doi: 10.1034/j.1399-5618.2000.020201.x

Shizuka, D., and Hudson, E. J. (2020). To accept or reject heterospecific mates: behavioural decisions underlying premating isolation. Philos. Trans. R. S. B Biol. Sci. 375:20190484. doi: 10.1098/rstb.2019.0484

Shohayeb, B., Diab, M., Ahmed, M., and Ng, D. C. H. (2018). Factors that influence adult neurogenesis as potential therapy. Transl. Neurodegen. 7:4. doi: 10.1186/s40035-018-0109-9

Shultz, S., and Dunbar, R. I. M. (2007). The evolution of the social brain: anthropoid primates contrast with other vertebrates. Proc. R. Soc. B Biol. Sci. 274, 2429–2436. doi: 10.1098/rspb.2007.0693

Silver, M., Sabini, J., and Parrott, W. G. (1987). Embarrassment - a dramarugic account. J. Theory Soc. Behav. 17, 47–61. doi: 10.1111/j.1468-5914.1987.tb00087.x

Song, H., Zhang, Y., Zuo, L., Chen, X., Cao, G., d’Oleire Uquillas, F., et al. (2019). Improving relationships by elevating positive illusion and the underlying psychological and neural mechanisms. Front. Hum. Neurosci. 12:526. doi: 10.3389/fnhum.2018.00526

Song, H. W., Zou, Z. L., Kou, J., Liu, Y., Yang, L. Z., Zilverstand, A., et al. (2015). Love-related changes in the brain: a resting-state functional magnetic resonance imaging study. Front. Hum. Neurosci. 9:13. doi: 10.3389/fnhum.2015.00071

Sorokowski, P., Sorokowska, A., Butovskaya, M., Karwowski, M., Groyecka, A., Wojciszke, B., et al. (2017). Love influences reproductive success in humans. Front. Psychol. 8:1922. doi: 10.3389/fpsyg.2017.01922

Sorokowski, P., Sorokowska, A., Karwowski, M., Groyecka, A., Aavik, T., Akello, G., et al. (2020). Universality of the triangular theory of love: adaptation and psychometric properties of the triangular love scale in 25 countries. J. Sex Res. 58, 106–115. doi: 10.1080/00224499.2020.1787318

Sorokowski, P., Zelazniewicz, A., Nowak, J., Groyecka, A., Kaleta, M., Lech, W., et al. (2019). Romantic love and reproductive hormones in women. International J. Environ. Res. Publ. Health 16:4224. doi: 10.3390/ijerph16214224

Spitzberg, B. H., and Cupach, W. R. (2003). What mad pursuit? Obsessive relational intrusion and stalking related phenomena. Aggr. Viol. Behav. 8, 345–375. doi: 10.1016/s1359-1789(02)00068-x

Sprecher, S., Aron, A., Hatfield, E., Cortese, A., Potapova, E., and Levitskaya, A. (1994). Love: american style, russian style, and japanese style. Pers. Relationsh. 1, 349–369. doi: 10.1111/j.1475-6811.1994.tb00070.x

Stephen, I. D., Burke, D., and Sulikowski, D. (2017). Tinbergen’s “four questions” provides a formal framework for a more complete understanding of prosocial biases in favour of attractive people. Behav. Brain Sci. 40, 38–39. doi: 10.1017/s0140525x16000650

Sternberg, R. J. (1986). A triangular theory of love. Psychol. Rev. 93, 119–135. doi: 10.1037/0033-295x.93.2.119

Sternberg, R. J. (1997). Construct validation of a triangular love scale. Eur. J. Soc. Psychol. 27, 313–335. doi: 10.1002/(sici)1099-0992(199705)27:3<313::Aid-ejsp824<3.3.Co;2-w

Sternberg, R. J., and Sternberg, K. (eds) (2019). The New Psychology of Love , 2nd Edn. Cambridge: Cambridge University Press.

Stewart-Williams, S., and Thomas, A. G. (2013). The ape that thought it was a peacock: does evolutionary psychology exaggerate human sex differences? Psychol. Inq. 24, 137–168. doi: 10.1080/1047840X.2013.804899

Stoessel, C., Stiller, J., Bleich, S., Boensch, D., Doerfler, A., Garcia, M., et al. (2011). Differences and similarities on neuronal activities of people being happily and unhappily in love: a functional magnetic resonance imaging study. Neuropsychobiology 64, 52–60. doi: 10.1159/000325076

Storey, A. E., Alloway, H., and Walsh, C. J. (2020). Dads: Progress in understanding the neuroendocrine basis of human fathering behavior. Hormon. Behav. 119:104660. doi: 10.1016/j.yhbeh.2019.104660

Stulp, G., Buunk, A. P., Pollet, T. V., Nettle, D., and Verhulst, S. (2013). Are human mating preferences with respect to height reflected in actual pairings? PLoS One 8:e54186. doi: 10.1371/journal.pone.0054186

Sugiyama, L. S. (2015). “Physical attractiveness: an adaptationist perspective,” in The Handbook of Evolutionary Psychology , 2nd Edn, ed. D. M. Buss (Cambridge: Cambridge University Press), 412–414.

Sullivan, R., Perry, R., Sloan, A., Kleinhaus, K., and Burtchen, N. (2011). Infant bonding and attachment to the caregiver: insights from basic and clinical science. Clin. Perinatol. 38, 643–655. doi: 10.1016/j.clp.2011.08.011

Sumter, S. R., Valkenburg, P. M., and Peter, J. (2013). Perceptions of love across the lifespan: differences in passion, intimacy, and commitment. Int. J. Behav. Dev. 37, 417–427. doi: 10.1177/0165025413492486

Swami, V., Stieger, S., Haubner, T., Voracek, M., and Furnham, A. (2009). Evaluating the physical attractiveness of oneself and one’s romantic partner individual and relationship correlates of the love-is-blind bias. J. Indiv. Differ. 30, 35–43. doi: 10.1027/1614-0001.30.1.35

Takahashi, K., Mizuno, K., Sasaki, A. T., Wada, Y., Tanaka, M., Ishii, A., et al. (2015). Imaging the passionate stage of romantic love by dopamine dynamics. Front. Hum. Neurosci. 9:191. doi: 10.3389/fnhum.2015.00191

Tarlaci, S. (2012). The brain in love: has neuroscience stolen the secret of love? Neuroquantology 10, 744–753. doi: 10.14704/nq.2012.10.4.581

Tennov, D. (1979). Love and Limerence: The Experience of Being in Love. New York, NY: Stein & Day.

Thomas, A. G., Jonason, P. K., Blackburn, J. D., Kennair, L. E. O., Lowe, R., Malouff, J., et al. (2020). Mate preference priorities in the East and West: a cross-cultural test of the mate preference priority model. J. Pers. 88, 606–620. doi: 10.1111/jopy.12514

Tinbergen, N. (1963). On aims and methods of Ethology. Zeitschrift Tierpsychol. 20, 410–433. doi: 10.1111/j.1439-0310.1963.tb01161.x

Todd, P. M., Penke, L., Fasolo, B., and Lenton, A. P. (2007). Different cognitive processes underlie human mate choices and mate preferences. Proc. Natl. Acad. Sci. U.S.A. 104, 15011–15016. doi: 10.1073/pnas.0705290104

Tomlinson, J. M., Aron, A., and Hatfield, E. (2018). “Romantic love,” in The Cambridge Handbook of Personal Relationships , eds A. L. Vangelisti and D. Perlman (Cambridge: Cambridge University Press).

Trivers, R. L. (1972). “Parental investment and sexual selection,” in Sexual Selection and the Descent of Man , ed. B. Campbell (Chicago, IL: Aldine), 136–179.

Turan, T., Uysal, C., Asdemir, A., and Kilic, E. (2013). May oxytocin be a trait marker for bipolar disorder? Psychoneuroendocrinology 38, 2890–2896. doi: 10.1016/j.psyneuen.2013.07.017

Ulmer-Yaniv, A., Avitsur, R., Kanat-Maymon, Y., Schneiderman, I., Zagoory-Sharon, O., and Feldman, R. (2016). Affiliation, reward, and immune biomarkers coalesce to support social synchrony during periods of bond formation in humans. Brain Behav. Immun. 56, 130–139. doi: 10.1016/j.bbi.2016.02.017

Van Londen, L., Goekoop, J. G., Zwinderman, A. H., Lanser, J. B. K., Wiegant, V. M., and De Wied, D. (1998). Neuropsychological performance and plasma cortisol, arginine vasopressin and oxytocin in patients with major depression. Psychol. Med. 28, 275–284. doi: 10.1017/s0033291797006284

Van Overwalle, F. (2009). Social cognition and the brain: a meta-analysis. Hum. Brain Mapp. 30, 829–858. doi: 10.1002/hbm.20547

Verhallen, A. M., Renken, R. J., Marsman, J. B. C., and ter Horst, G. J. (2019). Romantic relationship breakup: an experimental model to study effects of stress on depression (-like) symptoms. PLoS One 14:e0217320. doi: 10.1371/journal.pone.0217320

Wachtmeister, C.-A., and Enquist, M. (2000). The evolution of courtship rituals in monogamous species. Behav. Ecol. 11, 405–410. doi: 10.1093/beheco/11.4.405

Walker, R. S., Hill, K. R., Flinn, M. V., and Ellsworth, R. M. (2011). Evolutionary history of hunter-gatherer marriage practices. PLoS One 6:e19066. doi: 10.1371/journal.pone.0019066

Walster, E. H., and Walster, G. W. (1978). A New Look at Love. Reading, MA: Addison-Wesley.

Walter, K. V., Conroy-Beam, D., Buss, D. M., Asao, K., Sorokowska, A., Sorokowski, P., et al. (2020). Sex differences in mate preferences across 45 countries: a large-scale replication. Psychol. Sci. 31, 408–423. doi: 10.1177/0956797620904154

Walum, H., and Young, L. J. (2018). The neural mechanisms and circuitry of the pair bond. Nat. Rev. Neurosci. 19, 643–654. doi: 10.1038/s41583-018-0072-6

Wang, A. Y., and Nguyen, H. T. (1995). Passionate love and anxiety - a cross-generational study. J. Soc. Psychol. 135, 459–470. doi: 10.1080/00224545.1995.9712215

Wang, Y. Y., Xu, D. D., Feng, Y., Chow, I. H. I., Ng, C. H., Ungvari, G. S., et al. (2020). Short versions of the 32-item hypomania checklist: a systematic review. Perspect. Psychiatr. Care 56, 102–111. doi: 10.1111/ppc.12388

Weisman, O., Schneiderman, I., Zagoory-Sharon, O., and Feldman, R. (2015). Early stage romantic love is associated with reduced daily cortisol production. Adapt. Hum. Behav. Physiol. 1, 41–53. doi: 10.1007/s40750-014-0007-z

Williams, G. C. (2019). Adaptation and Natural Selection: A Critique of Some Current Evolutionary Thought. Princeton, NJ: Princeton University Press.

Winterhalder, B., and Smith, E. A. (1992). “Evolutionary ecology and the social sciences,” in Evolutionary Ecology and Human Behavior , eds E. A. Smith and B. Winterhalder (Hawthorne, NY: Aldine de Gruyter), 3–23.

Wooderson, S. C., Gallagher, P., Watson, S., and Young, A. H. (2015). An exploration of testosterone levels in patients with bipolar disorder. Bjpsych. Open 1, 136–138. doi: 10.1192/bjpo.bp.115.001008

Wrosch, C., and Miller, G. E. (2009). Depressive symptoms can be useful: self-regulatory and emotional benefits of dysphoric mood in adolescence. J. Pers. Soc. Psychol. 96, 1181–1190. doi: 10.1037/a0015172

Xu, X. M., Aron, A., Brown, L., Cao, G. K., Feng, T. Y., and Weng, X. C. (2011). Reward and motivation systems: a brain mapping study of early-stage intense romantic love in chinese participants. Hum. Brain Mapp. 32, 249–257. doi: 10.1002/hbm.21017

Xu, X. M., Brown, L., Aron, A., Cao, G. K., Feng, T. Y., Acevedo, B., et al. (2012a). Regional brain activity during early-stage intense romantic love predicted relationship outcomes after 40 months: an fMRI assessment. Neurosci. Lett. 526, 33–38. doi: 10.1016/j.neulet.2012.08.004

Xu, X. M., Wang, J., Aron, A., Lei, W., Westmaas, J. L., and Weng, X. C. (2012b). Intense passionate love attenuates cigarette cue-reactivity in nicotine-deprived smokers: an fMRI study. PLoS One 7:e42235. doi: 10.1371/journal.pone.0042235

Xu, X. M., Weng, X. C., and Aron, A. (2015). “The mesolimbic dopamine pathway and romantic love,” in Brain Mapping: An Encyclopedic Reference , eds A. W. Toga, M. M. Mesulam, and S. Kastner (Oxford: Elsevier).

Yancey, G., and Emerson, M. O. (2014). Does height matter? An examination of height preferences in romantic coupling. J. Fam. Issues 37, 53–73. doi: 10.1177/0192513X13519256

Young, K. A., Gobrogge, K. L., Liu, Y., and Wang, Z. X. (2011). The neurobiology of pair bonding: insights from a socially monogamous rodent. Front. Neuroendocrinol. 32:53–69. doi: 10.1016/j.yfrne.2010.07.006

Younger, J., Aron, A., Parke, S., Chatterjee, N., and Mackey, S. (2010). Viewing pictures of a romantic partner reduces experimental pain: involvement of neural reward systems. PLoS One 5:e13309. doi: 10.1371/journal.pone.0013309

Zaikman, Y., and Marks, M. J. (2017). Promoting theory-based perspectives in sexual double standard research. Sex Roles 76, 407–420. doi: 10.1007/s11199-016-0677-z

Zeifman, D. M. (2001). An ethological analysis of human infant crying: answering Tinbergen’s four questions. Dev. Psychobiol. 39, 265–285. doi: 10.1002/dev.1005

Zeki, S. (2007). The neurobiology of love. FEBS Lett. 581, 2575–2579. doi: 10.1016/j.febslet.2007.03.094

Zeki, S., and Romaya, J. P. (2010). The brain reaction to viewing faces of opposite- and same-sex romantic partners. PLoS One 5:e15802. doi: 10.1371/journal.pone.0015802

Zietsch, B. P., Sidari, M. J., Murphy, S. C., Sherlock, J. M., and Lee, A. J. (2020). For the good of evolutionary psychology, let’s reunite proximate and ultimate explanations. Evol. Hum. Behav . 42, 76–78. doi: 10.1016/j.evolhumbehav.2020.06.009

Zou, Z., Song, H., Zhang, Y., and Zhang, X. (2016). Romantic love vs. drug addiction may inspire a new treatment for addiction. Front. Psychol. 7:1436. doi: 10.3389/fpsyg.2016.01436

Zsok, F., Haucke, M., De Wit, C. Y., and Barelds, D. P. H. (2017). What kind of love is love at first sight? An empirical investigation. Pers. Relationsh. 24, 869–885. doi: 10.1111/pere.12218

Keywords : romantic love, mechanisms, ontogeny, functions, phylogeny, Tinbergen, human mating, definition

Citation: Bode A and Kushnick G (2021) Proximate and Ultimate Perspectives on Romantic Love. Front. Psychol. 12:573123. doi: 10.3389/fpsyg.2021.573123

Received: 16 June 2020; Accepted: 12 March 2021; Published: 12 April 2021.

Reviewed by:

Copyright © 2021 Bode and Kushnick. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Adam Bode, [email protected]

† ORCID: Adam Bode, orcid.org/0000-0003-4593-5179 ; Geoff Kushnick, orcid.org/0000-0001-9280-0213

Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

• Human Editing
• Free AI Essay Writer
• AI Outline Generator
• AI Paragraph Generator
• Paragraph Expander
• Essay Expander
• Literature Review Generator
• Research Paper Generator
• Thesis Generator
• Paraphrasing tool
• AI Rewording Tool
• AI Sentence Rewriter
• AI Rephraser
• AI Paragraph Rewriter
• Summarizing Tool
• AI Content Shortener
• Plagiarism Checker
• AI Detector
• AI Essay Checker
• Citation Generator
• Reference Finder
• Book Citation Generator
• Legal Citation Generator
• Journal Citation Generator
• Reference Citation Generator
• Scientific Citation Generator
• Source Citation Generator
• Website Citation Generator
• URL Citation Generator
• Proofreading Service
• Editing Service
• AI Writing Guides
• AI Detection Guides
• Citation Guides
• Grammar Guides
• Paraphrasing Guides
• Plagiarism Guides
• Summary Writing Guides
• STEM Guides
• Humanities Guides
• Language Learning Guides
• Coding Guides
• Top Lists and Recommendations
• AI Detectors
• AI Writing Services
• Coding Homework Help
• Citation Generators
• Editing Websites
• Essay Writing Websites
• Language Learning Websites
• Math Solvers
• Paraphrasers
• Plagiarism Checkers
• Reference Finders
• Spell Checkers
• Summarizers
• Tutoring Websites

Most Popular

Ai or not ai a student suspects one of their peer reviewer was a bot, how to summarize a research article, loose vs lose, how to cite a blog, apa paraphrasing, what is love essay sample, example.

The word “love” has gone through various dictionary definitions throughout the eons. According to the Harvard Crimson, “The roots of the word “love” can be traced back to the Indo-European root leubh, meaning “to care” or “to desire,” approximated from words including the Latin lubet, “it pleases” and the Sanskrit lubhyati, “he desires.” Along with “love,” related English words like “libido” and “belief” also descend from *lebuh. According to The Bloomsbury Dictionary of Words, while the word “love” initially meant “find pleasing,” it later took on associations with “praise,” “trust” and “belief”’ (Cocola, Jim). This follows a common pattern in romantic relationships that begins with pleasure, progresses to admiration, and finally becomes about trust. We can look at history to see that humanity has considered love to be, in essence, a variety of virtues and feelings. To say one sentence about love is seemingly impossible. That is why is important to differentiate between the types of love we humans experience.

What constitutes “pure love” is highly debatable. Religious or spiritual people will say “pure love” is that love which is divinely inspired or related to the divine. Other people will say friendship is the truest love of all. While others will say unconditional love is the only pure form of love. There is no consensus on what constitutes “pure love,” however there are similarities between the definitions. Most ideas about what “pure love” is circles around the concept of something transcendent. This variety of love is commonly above attachment, hate, codependency, and other forms of limitations.

Perhaps the most famous depictions of love in the western world are discussed by Plato, Aristotle, and other historical sources. We can say there are seven flavors of love: romantic love, friendship, familial love, universal love, uncommitted love, practical love, and self-love. Romantic love is marked by passion and sometimes lust between people to create a bond. Love based on friendship, on the other hand, can be said to be shared goodwill, companionship, trust, and more. In a similar vein, familial love is carved out of dependency and familiarity, and is almost automatic. Another type of love that is commonly inbuilt is universal love. This slice of love is based on feeling care for God, strangers, nature, and other encompassing factors. It can also relate to altruism, where we want to help others in need, even if we do not know them well, or do not expect something in return. A more baser type of love is uncommitted love, which involves teasing, flirting, seducing, and sex without attachments. The opposite comes in the form of shared interests and duties with practical love. Often, people are drawn towards each other based on activities, hobbies, professions, and other factors. This can form a strong bond between two or more people at a time. Lastly, self-love is controversial. It can be said to be healthy with self-affirmation and self-confidence, but unhealthy with narcissism and vanity (“These Are the 7 Types of Love”).

All of these types of loves intermix in our lives. It is difficult to find someone who does not have all these flavors of love present in his or her experience of reality. However, it is up to us to determine the most significant type of love and to search for it. Commonly, figuring out what this most important flavor of love is will indicate what we need to do with our lives, how we need to act, and how we want to construct our family and work lives. Therefore, knowing what love is to you is not only a philosophical pursuit but also a practical one.

A definition essay sometimes can get confused with a description writing. That’s why it’s essential to check out some samples before starting your work. Some best assignment writer sites can provide you with a whole collection of similar examples.

Works Cited

Cocola, Jim. “Redefining Love.” The Harvard Crimson, www.thecrimson.com/article/1998/2/9/redefining-love-pi-adore-you-i/.

“These Are the 7 Types of Love.” Psychology Today, Sussex Publishers, www.psychologytoday.com/us/blog/hide-and-seek/201606/these-are-the-7-types-love.

Follow us on Reddit for more insights and updates.

Comments (0)

Welcome to A*Help comments!

We’re all about debate and discussion at A*Help.

We value the diverse opinions of users, so you may find points of view that you don’t agree with. And that’s cool. However, there are certain things we’re not OK with: attempts to manipulate our data in any way, for example, or the posting of discriminative, offensive, hateful, or disparaging material.

Cancel reply

Your email address will not be published. Required fields are marked *

Save my name, email, and website in this browser for the next time I comment.

More from Definition Essay Examples and Samples

Oct 25 2023

What Is Identity? Definition Essay Sample

Oct 23 2023

What Is Respect? Definition Essay Example

Oct 20 2023

What Is a Home? Essay Definition Examples

Related writing guides, writing a definition essay.

Remember Me

What is your profession ? Student Teacher Writer Other

Forgotten Password?

Username or Email

Essay on Love

Students are often asked to write an essay on Love in their schools and colleges. And if you’re also looking for the same, we have created 100-word, 250-word, and 500-word essays on the topic.

Let’s take a look…

100 Words Essay on Love

Understanding love.

Love is a powerful emotion, felt by all creatures. It’s a bond that connects us, making us care deeply for others. From family to friends, we experience love in different forms.

Types of Love

There are many types of love. We love our family unconditionally, our friends deeply, and our pets loyally. This shows love’s versatility.

The Power of Love

Love can bring happiness, comfort, and warmth. It can heal wounds and bring peace. The power of love is truly magical.

Love’s Challenges

Love isn’t always easy. It can bring pain and heartache. But overcoming these challenges strengthens love.

Love is a beautiful journey, filled with joy and challenges. It’s a fundamental part of life.

Also check:

• 10 Lines on Love
• Paragraph on Love
• Speech on Love

250 Words Essay on Love

The essence of love.

Love, a universal sentiment, is a complex and multidimensional concept that has been the subject of countless discourses and studies. It is a powerful emotion, a binding force that transcends physicality and enters the realm of the spiritual.

The Multifaceted Nature of Love

Love is not monolithic; it is multifaceted and varies in intensity and expression. It can be romantic, platonic, familial, or self-love. Each type is vital and contributes to our overall well-being. Romantic love, for instance, is often characterized by passion and intimacy. Platonic love, on the other hand, is grounded in intellectual connection and shared interests.

The Transformative Power of Love

Love has the power to transform individuals and societies. It fosters empathy, kindness, and understanding, breaking down barriers and promoting unity. Love can heal wounds, mend broken hearts, and inspire acts of selflessness and sacrifice. It is the catalyst for human growth and the foundation of our humanity.

Despite its beauty, love is not without challenges. It can lead to heartbreak, disappointment, and despair. However, these trials are part of the journey of love, teaching us resilience and the value of vulnerability.

The Enduring Mystery of Love

Despite our attempts to understand and define love, it remains a profound mystery. It is an experience that is deeply personal yet universally shared, a paradox that adds to its allure. Love, in its essence, is an exploration of the depths of the human heart, a journey into the soul’s innermost chambers.

In conclusion, love is a multifaceted, transformative, and enduring emotion that shapes our lives in profound and intricate ways. It is the essence of our humanity, a testament to our capacity for empathy, compassion, and connection.

500 Words Essay on Love

The concept of love.

Love, a four-letter word that encapsulates a plethora of emotions, is a universal concept that transcends all barriers. It is a deeply personal and subjective experience, yet it also serves as a communal bond that ties societies together. The complexity of love is such that it can be viewed from various perspectives, including biological, psychological, and philosophical.

Biological Perspective of Love

From a biological standpoint, love is a potent cocktail of chemicals. Neurotransmitters such as oxytocin and dopamine are primarily responsible for the feelings of attachment and pleasure associated with love. The release of these chemicals in the brain creates a sense of euphoria, leading to the emotional highs that are often associated with romantic love. This biochemical perspective, however, only scratches the surface of the profound complexity of love.

Psychological Perspective of Love

Psychologically, love is a dynamic process that evolves over time. According to Sternberg’s Triangular Theory of Love, it consists of three components: intimacy, passion, and commitment. Intimacy refers to feelings of closeness and connectedness, passion involves intense feelings and sexual attraction, while commitment refers to the decision to remain with another. The balance between these components determines the type of love one experiences, ranging from infatuation (passion alone) to consummate love (a balance of all three).

Philosophical Perspective of Love

Philosophically, love is often viewed as an existential need. It is seen as a path to self-discovery and personal growth. The philosopher Plato suggested that love is the pursuit of the whole, a quest for completeness. This idea is echoed in the concept of ‘soulmates’ prevalent in popular culture. Yet, love is not solely about finding the ‘missing piece’; it is also about selflessly caring for another, seeking their happiness, and accepting them unconditionally.

Love as a Social Construct

Beyond individual experience, love is a social construct that shapes societal norms and values. It is a driving force behind many cultural practices and traditions. Love is celebrated through literature, music, and art, reflecting its deep-rooted significance in human society. It is a catalyst for social cohesion, fostering empathy and mutual understanding among individuals.

Conclusion: The Complexity and Importance of Love

In conclusion, love is a multifaceted concept that cannot be confined to a single definition. It is a biological process, a psychological state, a philosophical pursuit, and a societal bond. It is a complex interplay of emotions, thoughts, and behaviors that profoundly influences our lives. Despite its complexity, or perhaps because of it, love remains one of the most enduring and universal aspects of the human experience. It is a testament to the depth and breadth of our capacity for connection, compassion, and growth.

That’s it! I hope the essay helped you.

If you’re looking for more, here are essays on other interesting topics:

• Essay on Lord of the Flies
• Essay on Living Sustainably in Harmony with Nature
• Essay on Living Abroad

Apart from these, you can look at all the essays by clicking here .

Happy studying!

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Save my name, email, and website in this browser for the next time I comment.

• Essay Samples
• College Essay
• Writing Tools
• Writing guide

Creative samples from the experts

↑ Return to Essay Samples

Definition Essay: Love

Love is something that means very different things to different people. For some, love can be purely romantic, or even purely sexual. For others, real love is utterly unconditional and only truly exists between family members, or between people and a deity. And for some people, love is fluid, ever changing, and everywhere, and is felt for family, friends, partners, pets, and even inanimate objects, dead artists, and fictional characters. None of these people would be right or wrong, but one thing is certain: love is the most powerful force in the entire universe.

Between partners of any description, be they married or cohabiting, boyfriend and girlfriend, straight or gay, young or old, love is a relationship of mutual understanding and respect. Marriages and partnerships are often built on common ground that people find when they first meet; this can be as deep as sharing religious, philosophical or religious beliefs, or as simple as finding that you love the same film, book, or band.

This kind of love is often reliant on some kind of ‘chemistry’: that strange feeling that they give you in the pit of your stomach, and the feeling that nothing in the world is more important to you than enjoying the moment you’re in together. Some people feel that they experience love at first sight, where they know from the minute they set eyes on each other that they want to to be with that person, but something built on common interests and understanding must be stronger.

A parent’s love for a child can also often be described as love at first sight, but this is very strong because it comes from a natural instinct to protect our offspring. This love can often start before the baby is even born: you only have to look at the pride and excitement of many parents-to-be when they have their scans and feel their baby kick for the very first time. This kind of love is also felt by a child for its mother; it is unconditional for at least the first few years of life, and can also be felt between siblings.

It is the strength of this feeling that makes love the most powerful emotion that most of us will ever experience. People can do some dreadful things out of hate and fear, but love can push us to do much, much worse. And it is often love that can cause us to hate, whether it’s out of jealousy, or anger because our loved one has been hurt. Love, ultimately, is a sacrifice, whatever the relationship, and it must be the most powerful force in the universe because as human beings, we make true sacrifices for nothing less.

Follow Us on Social Media

Get more free essays

Send via email

Most useful resources for students:.

• Free Essays Download
• Writing Tools List
• Proofreading Services
• Universities Rating

Contributors Bio

Find more useful services for students

Free plagiarism check, professional editing, online tutoring, free grammar check.

• Share full article

Advertisement

Supported by

On Location

A Second Home That’s Far Away From It All

Two saltbox houses on the island of Newfoundland, in Canada, were hard to resist. What would be harder still: Renovating them without road access.

A Remote Escape in Newfoundland

View Slide Show ›

By Tim McKeough

When Cailey Heaps wants to get away from it all, one place comes to mind: the island of Newfoundland in Canada.

Although she spends most of the year in Toronto, where she runs the real estate brokerage Heaps Estrin and raises her three children — 17-year-old Mimi and 13-year-old twins Declan and Pippa — the craggy, saltwater-sprayed eastern coast of Newfoundland has long held special appeal.

“It’s this very romantic, peaceful part of the world where it feels like time moves at a different pace,” said Ms. Heaps, 47. “I can go there for three days and feel like I’ve taken a two-week holiday.”

In 2021, she was considering buying a country house within an easy drive of Toronto, but the siren song of Newfoundland beckoned. Diving into the listings, she was surprised to find one with a pair of the most quintessential Newfoundland saltbox houses she’d ever seen.

The two white houses, built in 1912 and 1914, were on a property in Salvage, a tiny coastal town with a population of 108, along with three red sheds, a small cemetery and an outhouse at the end of a dock with a hole directly above the water. The parcel was across the harbor from the center of town, on Burden’s Point, but highly visible, and it had been on the market for years. It had even been the subject of news stories focused on worries that the houses might be torn down.

Stuck in Toronto, Ms. Heaps asked her friend and Newfoundland real estate agent Chris O’Dea what he thought of it. “Chris said, ‘Cailey, this is a big project. It’s not what you’re picturing. It’s a massive undertaking. There’s no road access. It’s boat and foot access only,’” Ms. Heaps said. “But I thought to myself, ‘Oh, how bad can it be?’”

She decided to buy it without seeing it in person after a local contractor told her that the buildings could likely be restored for about 250,000 Canadian dollars ($184,000). She closed in March 2022 for 235,000 Canadian dollars ($173,000). Then she asked Reflect Architecture , a Toronto-based studio run by Trevor Wallace, to breathe new life into the structures.

“We went out there to check them out,” Mr. Wallace said. “And, just like with anything that old, there were a lot of surprises.”

Upstairs, the ceilings were about six feet high, so he couldn’t even stand up. Much of the wooden clapboard siding was so soft you could poke a finger through it. The sheds looked ready to topple over.

“Everything was very rickety,” he said. “They had just had a hundred years of good old Newfoundland battering.”

Back in Toronto, Mr. Wallace began drawing up plans to update the two houses and make them comfortable for a new generation, while retaining as much character as possible. The plan was to use the larger, 1,060-square-foot house, which had no electricity or plumbing, as the main living space and Ms. Heaps’s primary suite. The 915-square-foot house — which had a few modern touches, like electricity and a flushing toilet — would become sleeping quarters for her children and a media room.

The architects took pains to preserve the buildings’ exterior appearance: They added new white clapboard siding that mimics the original siding and standing-seam metal roofs. They maintained the original window openings but, inspired by the Canadian painter Christopher Pratt , added new energy-efficient window units with deep jambs to create more striking shadows on sunny days. They added a new window to Ms. Heaps’s bedroom that looks out toward the water and isn’t visible from town, and designed wraparound decks.

Inside, the upstairs ceilings were pushed into the attics for more headroom, and layers of wallpaper were peeled away to reveal the original wood paneling. And new rough-hewed wood was installed in areas where the original paneling turned out to be oddly shaped scraps of leftover lumber.

To give the houses a simple, stylish look while keeping costs down, they got creative with paint. Most of the interiors are painted white, but various saturated colors — muddy gray, forest green, royal blue, peachy pink — define the staircases and bedrooms. The streamlined kitchen has birch plywood cabinets and counters made of butcher block.

Outside, they restored one of the sheds to serve as a future artist’s studio and dismantled the other two, along with the outhouse. Because there is still no road, all of the building materials had to be brought in and out by boat.

Even with such basic material choices and compromises, the construction cost more that Ms. Heaps expected. By the time the work was complete in May 2023, it had ballooned to about 1 million Canadian dollars ($735,000) — quadruple the initial estimate. But it’s money well spent to Ms. Heaps, who is recouping some of her investment by renting out the property on Airbnb when she isn’t using it.

“It’s the most unique setting I’ve ever seen,” she said. “You go out the back door, up the hill and come to a lookout where all you see is ocean, trees and whales. It’s a magical place.”

For weekly email updates on residential real estate news, sign up here .

The State of Real Estate

Whether you’re renting, buying or selling, here’s a look at real estate trends..

A lot of change is happening in the housing market. Here’s the outlook .

With a landmark legal settlement  poised to upend a decades-old norm that has dictated who pays real estate agents and how much, economists, agents and lenders are beginning to worry that the burden could now be on first-time home buyers .

American homeowners could see a significant drop  in the cost of selling their homes  after a real estate trade group agreed to a landmark deal  that would eliminate the standard 6% sales commission.

A pricey housing market and higher interest rates have made it harder to afford a house, but so-called closing costs — for items like loan origination fees, discount points, appraisal and credit report fees — are also adding to the challenge .

As the prices for office space in urban centers tumble, cities whose municipal budgets rely on taxes associated with commercial real estate are starting to bear the brunt .

Homeowners are adding hidden doors and rooms to foil burglars, eke out extra storage space and prepare for Armageddon .