a researcher measures the galvanic skin response

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What Is the Galvanic Skin Response (GSR)?

Conditions treated.

The galvanic skin response (GSR), also known as electrodermal activity (EDA) or skin conductance, measures electrical changes in the skin caused by sweat gland activity in the palms and fingers. It can provide important information about the body’s level of physiological arousal, or activation and excitement, in response to stimuli.  

The galvanic skin response is typically used in medical research or in a type of treatment known as biofeedback therapy. Learn more about the galvanic skin response, including its definition, uses, and conditions treated.

John Fedele / Getty Images

The galvanic skin response measures the skin’s electrical changes in response to sweat gland activity in the fingers and palms. The skin tends to become a “better” conductor of electricity when you experience something intense or out of the ordinary—that is, when you are physiologically aroused.

GSR is an indicator of autonomic (involuntary) bodily response. When exposed to external or internal stimuli—such as sound, light, temperature, emotions, words, and faces—your body reacts involuntarily.  

As your level of physiological arousal (meaning activation) changes, so do your autonomic responses. Arousal can be positive, negative, or neutral. For example, people tend to sweat more when they are hot, excited, or emotionally stressed. Pupils dilate when someone enters a dark room or when they see someone they are attracted to.  

What Is the Autonomic Nervous System?

The autonomic nervous system regulates the actions of the body’s glands and smooth muscles, such as the reproductive organs and the circulatory, respiratory, and digestive systems. It includes the parasympathetic and sympathetic nervous systems.

The parasympathetic nervous system controls functions like sleep, sex, pleasure, and eating. Meanwhile, the sympathetic nervous system —which produces the galvanic skin response—helps to control the fight-or-flight response.

Galvanic skin response is usually measured with pain-free sensors placed on the body, often on the hands, feet, and/or fingers. Certain wearable devices, such as specially designed gloves and watches, may also be used to measure changes in skin conductance. Data about the galvanic skin response is also sometimes used in virtual reality (VR)–based therapy.

GSR information is sometimes used to gather data as part of medical research. For example, a 2020 study found that people in the intensive care unit (ICU) experienced positive changes in GSR signals in response to attention from a nurse or family member, even while in a coma. This information could be used to help to improve treatment in the ICU in the future.

Researchers and healthcare providers also sometimes measure the galvanic skin response as part of biofeedback therapy. Biofeedback therapy is a process that involves measuring the body’s physiological responses, such as heart rate, breathing, temperature, and sweating.

The person being treated gets real-time audio or visual feedback about their physiological responses. Over time, biofeedback therapy aims to gain more control over involuntary bodily functions to develop better coping skills, reduce symptoms, and treat certain conditions.

Information about the galvanic skin response has been used to treat a number of conditions, often as an aspect of biofeedback therapy or to gather more information about particular symptoms. Researchers have used GSR data to treat and learn more about the following:

• Epilepsy : Research indicates that GSR biofeedback therapy can be effective in reducing seizure frequency among people with epilepsy. Biofeedback training is sometimes used to treat people with drug-resistant epilepsy or as a complementary therapy alongside anti-seizure medications .
• Headache : GSR biofeedback therapy may help to reduce the symptoms of chronic headache , especially for people with tension-induced headaches.
• Hyperhidrosis (excessive sweating) : Studies indicate that wearable biosensors that measure GSR and sweat loss may effectively reduce excessive sweating in cases of hyperhidrosis .
• Hypertension (high blood pressure) : In a 2020 study, people with hypertension experienced a drop in blood pressure after a nurse-led, home-based intervention that included GSR biofeedback therapy and deep breathing exercises.
• Anxiety : The galvanic skin response often plays a key role in anxiety and tension. GSR biofeedback can help people with anxiety disorders, such as phobias , learn to relax their muscles and soothe themselves in moments of stress or panic.
• Schizophrenia : Several studies have found that biofeedback training can help improve certain social and cognitive skills . For example, a 2020 study found that GSR biofeedback therapy improved concentration and attention among young men with schizophrenia.
• Post-traumatic stress disorder (PTSD) : In addition to measurements of heart rate and body temperature, data about the galvanic skin response is often helpful in the study of novel treatments for PTSD .  
• Dementia : A 2021 study indicated that older adults with certain types of dementia, such as Alzheimer’s disease , experienced positive changes in galvanic skin response, heart rate, breathing, and other signs of stress or arousal after receiving care from a specially designed “social robot.”
• Traumatic brain injury (TBI): The preliminary results from an ongoing study suggest that wearable biofeedback devices may decrease anxiety, increase self-esteem, boost mindfulness, and improve well-being among people with traumatic brain injuries and related medical complications.
• Chronic pain : A 2019 study found that people with chronic pain experienced a reduction in both pain and inflammation after wearing an electrodermal biofeedback device for three weeks.
• Nausea : Relaxation exercises that involve GSR biofeedback are helpful in the treatment of various types of nausea, including motion sickness , chemotherapy-related nausea, and pregnancy-related morning sickness .
• Tourette's syndrome : Some early research suggests that GSR biofeedback training may help prevent tics (involuntary movements or sounds) among people with Tourette's syndrome.
• Diabetes : Studies have found that GSR biofeedback may help some people with type 2 diabetes control their glucose levels and their related stress and anxiety symptoms.

Galvanic Skin Response and Epilepsy

Biofeedback therapy using data about the galvanic skin response has been found to be particularly effective in the treatment of epilepsy . One 2019 systematic review and meta-analysis found that people who received biofeedback training using GSR measurements experienced a 64% reduction in seizure frequency on average.

The galvanic skin response (GSR), sometimes known as skin conductance or electrodermal activity (EDA), refers to changes in the skin’s electrical and sweat gland activity in response to physiological arousal (activation). It is typically measured with sensors placed on the skin, often as part of a wearable device.

In some cases, the galvanic skin response is measured in order to gather data for medical research. Galvanic skin response signals are also measured as part of biofeedback therapy. GSR biofeedback can help to treat conditions like epilepsy, schizophrenia, dementia, and anxiety , among others.

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Altıntop ÇG, Latifoğlu F, Akın AK, İleri R, Yazar MA. Analysis of consciousness level using galvanic skin response during therapeutic effect .  J Med Syst . 2020;45(1):1. doi:10.1007/s10916-020-01677-5

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By Laura Dorwart Dr. Dorwart has a Ph.D. from UC San Diego and is a health journalist interested in mental health, pregnancy, and disability rights.

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Galvanic Skin Response (GSR): The Complete Pocket Guide

Table of Contents

What is gsr (galvanic skin response).

The skin tells everything – our skin gives away a lot of information on how we feel when we’re exposed to emotionally loaded images, videos, events, or other kinds of stimuli – both positive and negative. No matter whether we are stressed, nervous, fearful, psyched up, stoked, baffled, or surprised – whenever we are emotionally aroused, the electrical conductivity of our skin subtly changes.

One of the most sensitive measures for emotional arousal is Galvanic Skin Response (GSR) , also referred to as Electrodermal Activity (EDA) or Skin Conductance (SC) .

Galvanic Skin Response originates from the autonomic activation of sweat glands in the skin. The sweating on hands and feet is triggered by emotional stimulation: Whenever we are emotionally aroused, the GSR data shows distinctive patterns that are visible with bare eyes and that can be quantified statistically.

What makes GSR such a valuable biometric signal in assessing emotional behavior?

With GSR, you can tap into unconscious behavior that is not under cognitive control. Skin conductivity is solely modulated by autonomic sympathetic activity that drives bodily processes, cognitive and emotional states as well as cognition on an entirely subconscious level. Exactly this circumstance renders GSR the perfect marker for emotional arousal as it offers undiluted insights into physiological and psychological processes of a person.

N.B. this post is an excerpt from our Galvanic Skin Response Pocket Guide. You can download your free copy below and get even more insights into the world of Galvanic Skin Response. Scroll to the bottom of the page for your free download.

Skin & Sweat

To understand how GSR works, take a quick step back and have a look at the physiological characteristics of the largest organ of the human body – the skin. Our skin functions as the principal interface between organism and environment. Together with other organs, it is responsible for bodily processes such as the immune system, thermo-regulation, and sensory-motor exploration:

1. Immune System As a protective barrier, the skin separates our body from the environment and its threats – mechanical impacts and pressure, variations in temperature, micro-organisms, radiation, and chemical agents.

2. (Thermo-)Regulation The skin controls body temperature by regulating sweat emission, piloerection (“goosebumps”), and peripheral blood circulation.

3. Sensing and Perception The skin is an organ of perception. It contains an extensive network of nerve cells that detect and relay changes in the environment based on the activity of receptors for temperature, pressure, and pain.

Consistent with this complexity of function, the skin has three primary layers:

• Epidermis (outmost protective layer)
• Dermis (cushion for the body from stress and strain)
• Hypodermis (anchor to bones and muscles)

Our body has about three million sweat glands. The density of sweat glands varies markedly across the body, being highest on the forehead and cheeks, the palms and fingers as well as on the sole of the feet.

Whenever sweat glands are triggered and become more active, they secrete moisture through pores towards the skin surface. By changing the balance of positive and negative ions in the secreted fluid, electrical current flows more readily, resulting in measurable changes in skin conductance (increased skin conductance = decreased skin resistance).

This change in skin conductance is generally termed Galvanic Skin Response (GSR) .

Galvanic Skin Response (GSR)

Galvanic Skin Response reflects the variation in the electrical characteristics of the skin.

GSR is also known as Skin Conductance (SC), Electrodermal Activity (EDA), Electrodermal Response (EDR) and Psychogalvanic Reflex (PGR)

GSR activity is typically measured in “micro-Siemens (uS)” or “micro-Mho (uM)”, mirroring the conductance of a certain material.

While the primary purposes of sweat emission are thermoregulation and evaporative cooling, sweating on hands and feet is also triggered whenever we’re emotionally aroused.

Emotional sweating?

Yes, you heard right. Let’s explain.

Like other vegetative auto-regulatory processes (body temperature, heart rate, blood pressure, gut motility etc.) sweat secretion cannot be controlled consciously. Rather, it is driven and balanced by our autonomic nervous system in order to meet behavioral demands (to prepare and execute energetic movement, for example).

Most broadly, the autonomic nervous system can be separated into the following two “subdivisions”:

The sympathetic nervous system represents a rapid response mobilizing system, facilitating immediate motor action (“fight or flight”). Increased sympathetic activity is associated with bodily indicators of “autonomic arousal” such as increased heart rate, blood pressure, and sweating.

The parasympathetic nervous system regulates slowly changing processes associated with „resting and digesting“ or „feeding and breeding“.

Let’s recap!

Sweat secretion and the associated changes in skin conductance are nonconscious processes that are solely under sympathetic control and reflect changes in arousal.

GSR & emotional arousal

So far, so good: Emotional experiences trigger changes in autonomic arousal quite impressively. Now what does that mean exactly?

Exposure to fear-inducing stimuli (an angry face, the sight of a creepy spider etc.) induce emotional arousal, causing an increase in sweat secretion and, ultimately, measurable electrodermal activity.

In emotional situations, bodily processes are triggered automatically : The heart beats faster, the pulse rises, hands become sweaty. To put it bluntly: While we are physiologically or psychologically aroused (in fear, extreme joy or under stress), we start to sweat.

In case you were thinking sweat running down in streams, let‘s give the all-clear here: Actually, we don‘t need to be sweat-flooded in order to see differences in electrodermal activity (in fact, the sweating doesn’t even need to be visible).

Besides emotional stimulus properties, recent findings indicate that skin conductance is also sensitive towards other aspects of a stimulus .

Are we familiar with the stimulus or do we encounter it for the first time? Is the stimulus threatening or rewarding? Do we associate the stimulus with wins or losses, love or hate, anticipation and outcome, memory recall or cognitive work? Against this backdrop, changes in skin conductance might also reflect motivational and attentional processing .

Application fields of GSR

“By 1972, more than 1,500 articles on GSR had been published in professional publications, and nowadays GSR is regarded as the most popular method for investigating human psychophysiological phenomena.” Boucsein (2014)

With GSR, the impact of any emotionally arousing content, product or service can be tested – actual physical objects, videos, images, sounds, odors, food probes and other sensory stimuli as well as thought experiments and mental images.

Paired with the fact that GSR responses are extremely easy to measure , possible applications cover a fascinating variety of fields in academic and commercial research.

Psychological Research Psychological studies utilize Galvanic Skin Response to identify how humans respond emotionally towards various stimuli and how these responses are affected by stimulus properties (color, shape, duration of presentation), personality characteristics (extraverts vs. introverts), social expectancies (“men are not afraid of the dark!”), and the interaction of cultural aspects and individual learning histories. Think of this: A terrifying encounter with the neighbor’s vicious dog in your childhood certainly triggers autonomous arousal and increased sweating when you come face to face with dogs in later life (perhaps even an image of a dog is enough to give you the creeps).

Clinical Research & Psychotherapy Clinical populations such as patients suffering from eating disorders, phobias or post-traumatic stress syndrome (PTSD) show heightened fear responses and emotional arousal to trauma reminders. Also, autonomous responses towards threatening stimuli typically do not subside even in the presence of safety reminders. Over the course of a cognitive-behavioral therapy, however, GSR can be monitored during exposition or relaxation trainings in order to provide a quantitative measure of the physiological arousal of the patient and assess the severity of the disease as well as the success of the therapeutic intervention.

Consumer Neuroscience & Marketing Evaluating consumer preferences is a critical element of marketing. GSR can be measured to track emotional arousal towards products with high consumer interest, however only subtle differences in terms of performance and quality. For example, shopping preferences and decisions in cosmetics are primarily based on affective and sub-conscious processes. With the help of Galvanic Skin Response recordings exactly these processes can be examined in more detail in order to enhance products, assess market segments or identify target audiences and personas.

Media & Ad Testing In media research, campaign material such as TV ads, trailers, and full-length shows can be shown to individual participants or focus groups while monitoring their emotional arousal based on Galvanic Skin Response measurements. Identifying key frames in the stimulus material or isolating scenes that “just don’t work” (where supposedly emotional content was shown but the audience did not respond) are just two of the many approaches to utilizing GSR for evaluation purposes.

Usability Testing & UX Design Using software should be a pleasant experience. Hence, frustration and confusion levels should certainly be kept as low as possible. Monitoring GSR can provide unfiltered insights into stress levels of users during the interaction with new website content, user interfaces, and online forms. How emotionally satisfying is the navigation? Whenever visitors encounter road blocks or get lost in complex sub-menus, you might certainly see increased stress levels reflected in stereotypic GSR activation patterns.

GSR sensors

Let‘s get practical with some good news: The observation of electrodermal phenomena requires only very basic equipment . However, there are a few things to keep in mind when it comes to choosing the right gear and applying it correctly.

Need of Galvanic Skin Response Sensor

With minimal preparation times and cleanup, skin conductivity is recorded non-invasively using two electrodes placed on the skin. This renders GSR measurements a lot more comfortable for respondents compared to other neuro-methods such as fMRI or EEG, where longer preparation and calibration phases are quite common (and sometimes a true hassle).

Generally, GSR sensors have a 1 cm² measurement site made of Ag/AgCl (silver/silver-chloride) and are placed either in reusable snap-on Velcro straps or in a patch sticker. While the former can be applied as-is, the patch sticker requires to use conductive gel in order to improve the conductivity between skin and electrode.

Logic Behind GSR Sensors

• Place two electrodes on emotionally sensitive locations on the body
• Apply a low constant voltage
• Measure the voltage difference between the two electrodes
• Report the associated skin conductance

What about the sampling rate?

Although GSR data might be acquired with arbitrary sampling rates (up 2000 Hz), already very low sampling rates are sufficient.

We suggest sampling rates from 1 or 10 Hz, however keep in mind that higher sampling rates might be necessary if the same device collects GSR and other physiological parameters such as (optical) heart rate, for example.

GSR devices

In case you are thinking bulky equipment, think again. In fact, GSR devices are quite the opposite.

They typically consist of two electrodes , an amplifier (to boost signal amplitude), and a digitizer (to transfer the analog raw signal into binary data streams). Wireless GSR devices further contain data transmission modules for communication with the recording computer (using the Bluetooth protocol, for example). Principally, GSR devices offer different sensor placement options. While some devices allow arbitrary sensor placements in any of the locations we have already mentioned, other devices have GSR electrodes rigidly mounted in wristbands or elastic straps.

There is no “one fits all” solution – it very much depends on your research question and the specific requirements of your study which sensor to pick in order to obtain the most appropriate GSR data.

However, irrespective of which GSR sensor you go for, it is always good advice to assess the quality of the GSR signal in the live viewer before you start the recording.

You can even examine the data together with the respondent in order to check for potential issues and visualize the impact of breathing, movements, and talking.

Setting it up

Here’s our handy checklist for the rather technical aspects of data collection:

1. Have you attached the GSR electrodes? Make sure that the sensors are properly attached to the fingers, hand or foot.

2. Have you wired up all cables correctly? Check if the electrode cables are not dangling loosely but are properly plugged into the correct sockets of your GSR device.

3. Is the GSR device up and running? You don’t believe how many experiments have been started with the GSR sensors still turned off. Spare yourself the hassle and make sure that the device is set to “on” and configured correctly.

4. Is the GSR device properly connected? GSR devices are either plugged in directly or are connected wirelessly, so always test if the connection has been established. Check if the Bluetooth dongle is properly plugged in and receives incoming data. As Bluetooth technology is a short-range wireless connection between two devices, take care of the following:

• Reception range Even if the transmitting GSR device and the Bluetooth receiver are in direct line of sight, try to stay in the recommended reception range (approximately 5 meters) as the connection is lost otherwise.
• Obstruction Bluetooth signals cannot pass through water, human tissue or concrete. This implies that the connection is dropped whenever respondents walk into neighboring rooms or occlude the sensor with their hand or body (we actually consist to 80% of water).

GSR reloaded: Adding more biosensors

What we know so far: Skin conductance offers tremendously valuable insights into our subconscious arousal when we‘re confronted with emotionally loaded stimulus material.

However, solely based on GSR we can‘t extract whether the arousal was due to positive or negative stimulus content. Why? The GSR peaks look completely identical. Both positive and negative stimuli can result in an increase in arousal triggering GSR peaks.

In other words: While GSR is an ideal measure to track emotional arousal, it is not able to reveal the emotional valence, that is, the quality of the emotions. The true power of GSR unfolds as it is combined with other sources of data to measure complex dependent variables and paint the full picure of emotional behavior.

The following 5 biosensors are a perfect complement to GSR recordings. Which metrics can be extracted from the different systems?

Eye tracking Eye tracking implies the recording of eye position (gaze point) and movement on a 2D screen or in 3D environments based on the optical tracking of corneal reflections. Eye tracking reflects visual attention as it objectively monitors where, when, and what respondents look at. Further, eye tracking devices report the dilation and constriction of the pupil, which has been found to correlate with emotional arousal and cognitive workload. Eye tracking therefore can be used to validate and compliment GSR measurements.

Facial expression analysis Facial expression analysis is a non-intrusive method to assess both emotions (subtle movements in face muscles, mostly subconscious) and feelings (accompanied by clearly noticeable changes in facial expression). While facial expressions can measure the valence of an emotion/feeling, they can’t measure the associated arousal.

EEG Electroencephalography is a neuroimaging technique measuring electrical activity on the scalp. EEG tells which parts of the brain are active during task performance or stimulus exposure. Analyze brain dynamics of engagement (arousal), motivation, frustration, cognitive workload and other metrics associated with stimulus processing, action preparation, and execution. EEG usually tracks stimulus-related processes much faster compared to other biosensors.

EMG Electromyographic sensors monitor the electric energy generated by bodily movements (e.g., of the face, hands or fingers). Use EMG to monitor muscular responses to any type of stimulus material to extract even subtle activation patterns associated with consciously controlled hand/finger movements (startle reflex). Also, facial EMG can be used to track smiles and frowns in order to infer one’s emotional valence.

The whole is more than the sum of its parts

Each biometric sensor reveals a specific aspect of human cognition emotion and behavior.

Depending on your individual research question, consider to combine GSR with two or more additional biosensors in order to gain meaningful insights into the intricate relationships between the autonomic regulation of emotional arousal and valence, cognition, attention and motivation.

N.B. This is an excerpt from our free guide “GSR – The Complete Pocket Guide ”. To get the full guide, follow the link below. 

Frequently asked questions

Can gsr sensors be integrated with other devices or software.

Yes, GSR sensors can be integrated with various devices and software, often used alongside other biometric measurements for comprehensive analyses.

What are the components of a GSR sensor?

The primary components of a GSR sensor include electrodes (typically made of silver or silver-chloride) for detecting skin conductance changes and wires or connections that relay this data to a data acquisition device.

Can Galvanic Skin Response equipment be used for biofeedback therapy?

Yes, Galvanic Skin Response equipment can be employed in biofeedback therapy to help individuals understand and control their physiological responses to stress or stimuli.

Free 36-page EDA/GSR Guide

For Beginners and Intermediates

• Get a thorough understanding of all aspects
• Valuable GSR research insights
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Evaluation of Galvanic Skin Response (GSR) Signals Features for Emotion Recognition

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• Cite this conference paper

• Kuryati Kipli   ORCID: orcid.org/0000-0002-4103-0674 10 ,
• Aisya Amelia Abdul Latip 10 ,
• Kasumawati Lias   ORCID: orcid.org/0000-0002-5534-0614 10 ,
• Norazlina Bateni   ORCID: orcid.org/0000-0001-6015-4739 10 ,
• Salmah Mohamad Yusoff   ORCID: orcid.org/0000-0002-5963-3019 11 ,
• Jamaah Suud 12 ,
• M. A. Jalil 13 ,
• Kanad Ray 14 ,
• M. Shamim Kaiser 15 &
• Mufti Mahmud 16  

Part of the book series: Communications in Computer and Information Science ((CCIS,volume 1724))

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• International Conference on Applied Intelligence and Informatics

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Over the years, physiological signals have shown its efficiency in emotion recognition. Galvanic skin response (GSR) is a quantifiable physiological signal generated from the change of skin conductance in response to emotional stimulation. Understanding human emotions through GSR signals can be a challenging task because of the characteristic’s complexity. The current performance on the analysis of GSR signals has yet to be satisfactory due to a lack of detailed evaluation on the performance of features extracted from GSR signals. Previous studies have compared the recognition rates between different physiological signals between electroencephalogram (EEG), electrocardiogram (ECG), and GSR as a group or focused on the performance of emotion recognition using a fusion of signals. This paper presents an evaluation of extracted features specifically from GSR signals from a public dataset named as AMIGOS database. The MATLAB software was used for the simulation. In the study, feature extraction techniques were performed to extract features in time domain and frequency domain features. These features are ranked using the one-way ANOVA method in MATLAB. Several subsets of different number of features based on the type of feature and significance level were formed for optimum selection. The state of art classification algorithm for GSR which is Support Vector Machine (SVM) was employed to evaluate the classification performance using the ranked features. The methodology proposed by this study was able to achieve high accuracy rates that are comparable with existing studies that had employed the same AMIGOS database. The frequency domain features achieved the highest accuracy for all four emotion classes.

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Kuryati Kipli, Aisya Amelia Abdul Latip, Kasumawati Lias & Norazlina Bateni

Faculty of Cognitive Sciences and Human Development, Universiti Malaysia Sarawak, 94300, Kota Samarahan, Malaysia

Salmah Mohamad Yusoff

Polytechnic Kuching Sarawak, 93050, Kuching, Sarawak, Malaysia

Jamaah Suud

Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, 81310, Skudai, Johor, Malaysia

M. A. Jalil

Amity School of Applied Sciences, Amity University, Rajasthan, 303001, India

Institute of Information Technology, Jahangirnagar University, Savar, Dhaka, 1342, Bangladesh

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Kipli, K. et al. (2022). Evaluation of Galvanic Skin Response (GSR) Signals Features for Emotion Recognition. In: Mahmud, M., Ieracitano, C., Kaiser, M.S., Mammone, N., Morabito, F.C. (eds) Applied Intelligence and Informatics. AII 2022. Communications in Computer and Information Science, vol 1724. Springer, Cham. https://doi.org/10.1007/978-3-031-24801-6_19

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Galvanic Skin Response in Emotion Research

This article explores the pivotal role of Galvanic Skin Response (GSR) in advancing our understanding of emotional processes within the domain of health psychology . The introduction provides a contextual backdrop, emphasizing the relevance of GSR as a physiological marker in emotion research. The subsequent section delves into the intricate physiology of GSR, elucidating the mechanisms underlying skin conductance and factors influencing its response patterns. The article then navigates through the myriad applications of GSR in health psychology, encompassing psychophysiological research, biofeedback interventions, and the assessment of treatment efficacy. A critical analysis of challenges and ethical considerations associated with GSR research is presented, accompanied by reflections on its limitations. The concluding section succinctly synthesizes key points, underscoring the ongoing significance of GSR in unraveling the complexities of emotional experiences. This article not only serves as an informative guide to GSR but also encourages further exploration and innovation in its application, laying the groundwork for future advancements in health psychology research.

Introduction

The Galvanic Skin Response (GSR) is a physiological phenomenon that reflects changes in the electrical conductance of the skin, primarily influenced by sweat gland activity. This involuntary response has garnered significant attention in the realms of health psychology and emotion research due to its potential as a reliable indicator of emotional arousal. GSR measurements are particularly sensitive to the autonomic nervous system’s sympathetic activity, making it a valuable tool for exploring the intricacies of emotional experiences. As individuals encounter various stimuli, their emotional responses elicit changes in skin conductance, providing researchers with a non-invasive means to assess emotional reactivity. The subsequent sections of this article delve into the physiological underpinnings of GSR, its influential factors, and the diverse methodologies employed in its measurement.

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This article serves a dual purpose: firstly, to underscore the pivotal role of GSR in comprehending emotional responses and, secondly, to establish a foundational understanding for its applications in health psychology. By elucidating the physiological mechanisms of GSR, researchers and practitioners gain insights into the intricate interplay between the autonomic nervous system and emotional states. Furthermore, the article aims to provide a comprehensive overview of the various contexts in which GSR can be applied within health psychology, ranging from psychophysiological research to biofeedback interventions. Ultimately, this exploration seeks to foster a deeper appreciation for the potential contributions of GSR to advancing our understanding of the complex interrelation between emotions and health.

Physiology of Galvanic Skin Response

The Galvanic Skin Response (GSR), also known as electrodermal activity, is a physiological measure reflecting changes in the electrical conductance of the skin. This response is commonly assessed through the use of electrodes placed on the skin surface, typically on the fingers or palm. The measurement techniques involve monitoring the variations in skin conductance resulting from the activity of eccrine sweat glands. GSR is particularly sensitive to alterations in sympathetic nervous system activity, making it a valuable tool for gauging emotional arousal.

The physiological basis of GSR lies in the intricate relationship between eccrine sweat glands and skin conductance. When an individual experiences emotional arousal, the sympathetic nervous system becomes activated, leading to an increase in sweat gland activity. As sweat is secreted onto the skin, it enhances the electrical conductivity of the skin’s surface. This heightened conductance is then measured by the electrodes, providing a quantifiable index of emotional responsiveness. Understanding the physiological mechanisms of GSR is essential for interpreting emotional reactivity in various contexts.

Emotional arousal plays a central role in modulating GSR. Intense emotions, such as fear, excitement, or stress, trigger heightened sympathetic activity, leading to increased sweat gland secretion and subsequently elevated skin conductance levels. GSR thus serves as a dynamic marker for emotional experiences, capturing the nuanced fluctuations in response to varying stimuli.

Beyond emotional states, external factors can influence GSR readings. Changes in ambient temperature and humidity levels can impact skin conductance, introducing variability into the measurements. Researchers must consider and control for these environmental factors to ensure the accuracy and reliability of GSR data in experimental settings.

Individuals exhibit diverse patterns of GSR responses, influenced by factors such as genetics, personality traits, and prior experiences. Some individuals may demonstrate heightened GSR reactivity to specific stimuli, while others may display more subdued responses. Investigating individual differences contributes to a comprehensive understanding of GSR as a psychophysiological marker.

GSR is employed in a variety of experimental designs to investigate emotional responses. Studies may utilize controlled stimuli, such as images, videos, or auditory cues, to elicit emotional reactions while monitoring GSR changes. Additionally, GSR can be integrated into real-life situations to capture naturalistic emotional experiences.

Techniques for collecting GSR data involve the placement of electrodes on specific skin sites, commonly the fingers or palm, to measure skin conductance. Data collection can be continuous or event-related, depending on the research design. Analyzing GSR data often includes assessing baseline levels, peak responses, and recovery phases. Advanced statistical methods, such as time-series analysis, are employed to derive meaningful insights from the dynamic nature of GSR measurements.

Understanding the intricate physiology of GSR, its influencing factors, and the diverse methodologies employed in its study lays the foundation for exploring its applications in health psychology and emotion research.

Applications of GSR in Health Psychology

GSR serves as an invaluable tool in psychophysiological research, particularly in the investigation of stress responses. By measuring changes in skin conductance, researchers can objectively assess the autonomic nervous system’s reactivity to stressors. GSR provides a dynamic index of the body’s immediate response to stress, offering insights into the intensity and duration of emotional arousal. This application of GSR aids in unraveling the complex interplay between psychological stressors and physiological reactions, contributing to a deeper understanding of the psychophysiology of stress.

The application of GSR extends beyond stress research to encompass various psychological disorders. GSR serves as a sensitive marker for emotional reactivity in conditions such as anxiety disorders, post-traumatic stress disorder (PTSD), and mood disorders. By identifying aberrations in GSR patterns, researchers can delineate distinctive physiological signatures associated with different disorders, potentially enhancing diagnostic precision and treatment strategies.

Biofeedback interventions leverage GSR as a prominent component in therapeutic practices. Through real-time monitoring of GSR, individuals gain awareness and control over their physiological responses. Biofeedback sessions, often facilitated by GSR measurements, empower individuals to modulate their emotional reactivity, promoting self-regulation and stress reduction. This application of GSR in biofeedback therapy exemplifies its potential as a practical and effective tool for enhancing emotional well-being.

The use of GSR in biofeedback extends to stress management and emotion regulation interventions. Individuals can learn to recognize early signs of emotional arousal through GSR feedback, facilitating the development of adaptive coping strategies. GSR biofeedback interventions have shown promise in promoting resilience to stress, improving emotion regulation skills, and fostering mental well-being in various populations.

GSR plays a crucial role in evaluating the effectiveness of interventions targeting emotional well-being. Whether through psychotherapy, mindfulness-based interventions, or pharmacological treatments, GSR provides an objective measure of changes in emotional reactivity over the course of treatment. Monitoring GSR allows researchers and clinicians to assess the immediate and long-term impact of interventions on emotional responses, aiding in the refinement of therapeutic approaches.

GSR not only assesses treatment outcomes but also contributes to understanding the mechanisms underlying therapeutic processes. By examining GSR patterns during therapeutic sessions, researchers can identify critical moments of emotional engagement, insight, or emotional release. This nuanced understanding enhances our comprehension of how therapeutic interventions influence emotional states at a physiological level, fostering advancements in evidence-based practice within health psychology.

The multifaceted applications of GSR in health psychology underscore its versatility as a psychophysiological marker, offering valuable insights into stress, emotional reactivity, and the efficacy of therapeutic interventions. These applications contribute to the development of targeted and personalized approaches in promoting mental and emotional well-being.

Challenges and Considerations in GSR Research

As GSR involves the collection of physiological data, concerns regarding participant privacy emerge. The recording of intimate physiological responses may raise ethical considerations, necessitating careful handling of sensitive information. Researchers must implement stringent data protection measures to ensure participant confidentiality, secure data storage, and ethical dissemination of findings, adhering to established guidelines and regulations.

Ethical GSR research requires transparent communication and obtaining informed consent from participants. Participants should be thoroughly briefed on the nature of GSR measurements, potential emotional responses elicited during experiments, and how their data will be used. Researchers must prioritize participant well-being, providing adequate debriefing procedures and support mechanisms to address any emotional distress that may arise during or after GSR experiments.

GSR readings exhibit considerable variability among individuals, influenced by factors such as personality traits, baseline emotional states, and prior experiences. This inherent individual variability poses a challenge in establishing universal benchmarks for emotional reactivity. Researchers must account for these differences in participant responses, employing statistical techniques and considering individual baseline measures to enhance the accuracy and reliability of GSR data interpretation.

The reliability of GSR measurements can be compromised by external factors, including ambient temperature, humidity, and environmental conditions. Fluctuations in these variables may introduce noise into GSR data, potentially confounding experimental results. Rigorous experimental control and calibration procedures are essential to mitigate the impact of external influences on GSR readings, ensuring the validity of the collected data.

The future of GSR research holds promise with ongoing technological advancements. Innovations in sensor technology, signal processing, and data analytics contribute to the refinement and portability of GSR measurement devices. These technological strides not only enhance the precision of GSR recordings but also expand the possibilities for real-time monitoring in naturalistic settings, fostering a deeper understanding of emotional experiences beyond the laboratory environment.

GSR research continues to evolve, opening avenues for further exploration and development. Future investigations could delve into the development of personalized GSR profiles, considering individual differences in emotional responsiveness. Additionally, exploring the integration of GSR with other physiological measures and neuroimaging techniques could provide a more comprehensive understanding of the neural and physiological correlates of emotional experiences. Further research is also warranted to elucidate the role of GSR in specific clinical populations and its potential as a diagnostic tool in mental health assessments.

Navigating the ethical landscape, addressing the inherent limitations, and embracing technological advancements are essential considerations for researchers engaging in GSR studies. The evolving landscape of GSR research holds the potential to deepen our understanding of emotional processes while concurrently addressing ethical concerns and methodological challenges.

The Galvanic Skin Response (GSR) emerges as a pivotal psychophysiological marker in health psychology, offering unique insights into the interplay between emotional experiences and physiological responses. GSR’s sensitivity to emotional arousal positions it as a valuable tool for researchers and practitioners seeking to understand the intricate dynamics of emotions within the realm of health.

The multifaceted applications of GSR underscore its versatility as a measure in health psychology. From its role in psychophysiological research, elucidating stress responses and emotional reactivity in various psychological disorders, to its application in biofeedback and intervention for stress management and emotion regulation, GSR proves to be a versatile and informative tool. Additionally, GSR’s utility extends to assessing treatment efficacy, providing valuable insights into the impact of interventions on emotional well-being.

As our comprehension of emotions deepens, the ongoing significance of GSR becomes increasingly evident. GSR not only provides a window into the immediate physiological responses associated with emotional experiences but also contributes to unraveling the complexity of emotional processes. Its role in studying stress, emotional reactivity, and therapeutic outcomes underscores its enduring importance in advancing the field of health psychology.

The conclusion of this article serves as a call to action, encouraging researchers and practitioners to embark on continued exploration and innovation in GSR applications within health psychology. The evolving landscape of technology and methodology offers opportunities to refine GSR measurements, explore novel applications, and uncover new dimensions of its utility. By fostering a culture of curiosity and innovation, the field can harness the full potential of GSR in enhancing our understanding of emotions and promoting holistic approaches to health and well-being.

In conclusion, GSR stands as a dynamic and informative tool, weaving together the threads of physiological and emotional experiences within the tapestry of health psychology. As the journey of discovery unfolds, the ongoing commitment to research and innovation ensures that GSR remains at the forefront of unraveling the intricate connections between emotions and health.

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Galvanic Skin Response (GSR)/Electrodermal/Skin Conductance Biofeedback on Epilepsy: A Systematic Review and Meta-Analysis

Affiliations.

• 1 Brighton and Sussex Medical School, University of Sussex, Brighton, United Kingdom.
• 2 Oxford Epilepsy Research Group, Nuffield Department of Clinical Neurosciences, NIHR Biomedical Research Centre, John Radcliffe Hospital, Oxford, United Kingdom.
• PMID: 31068887
• PMCID: PMC6491510
• DOI: 10.3389/fneur.2019.00377

Objectives: Dynamic changes in psychophysiological arousal are directly expressed in the sympathetic innervation of the skin. This activity can be measured as tonic and phasic fluctuations in electrodermal activity [Galvanic Skin Response (GSR)/skin conductance]. Biofeedback training can enable an individual to gain voluntary control over this autonomic response and its central correlates. Theoretically, control of psychophysiological arousal may be harnessed as a therapy for epilepsy, to mitigate pre-ictal states. Evidence is accumulating for the clinical efficacy of GSR biofeedback training in the management of drug resistant epilepsy. In this review, we analyse current evidence of efficacy with GSR biofeedback and evaluate the methodology of each study. Method: We searched published literature pertaining to interventional studies of GSR biofeedback for epilepsy, through MEDLINE and Cochrane databases (1950-2018). Using percentage seizure reduction as an indicator of therapeutic efficacy induced by GSR biofeedback, we used meta-analytic methods to summarize extant findings. We also compare and contrast study design with relevance to the interpretation of outcomes. Results: Out of 21 articles retrieved for GSR/EDA/Skin conductance biofeedback, four studies were identified as interventional trials, involving 99 patients with drug-resistant epilepsy in total. Three of these studies included a control group and a positive therapeutic effect of biofeedback was reported in each of these. The difference in seizure frequency percentage (Biofeedback-Control) was between -54.4 and -74.0% with an overall weighted mean difference of -64.3% (95% CI: -85.4 to -43.2%). The response rates (proportion of patients manifesting >50% reduction in seizure frequency) varied from 45 to 66% across studies. Significance: This timely evaluation highlights the potential value of GSR biofeedback therapy, and informs the optimal study design of larger scale studies that are now required to more definitively establish the utility of this non-invasive, non-pharmacological interventional approach for drug-resistant epilepsy.

Keywords: autonomic activity; behavioral therapy; biofeedback; electrodermal activity; epilepsy; galvanic skin response; skin conductance.

Publication types

• Systematic Review

Tobii Connect

• Galvanic skin response (GSR)

Concept 2023-May-17 • Knowledge Article

Information, table of contents.

1. Intro 2. Emotional sweating 3. GSR sensor 4. Response time of GSR changes 4.  GSR artifacts 5. GSR metrics  in Tobii Pro Lab 6. GSR data filtering in Tobii Pro Lab 7. References and recommended reading

GSR has been closely linked to the emotional state and arousal level of a participant and has been used as an index of non-conscious emotional intensity and cognitive processing. Some fields of research where GSR has been widely applied include emotion research (e.g., fear, threat, happiness), decision making research, clinical research (e.g., post-traumatic stress disorders, depression, autism), and usability and marketing research (e.g., product and media content evaluation).

GSR can be added to an eye tracking study without significant changes to the study design. For example, in TV media research, adding GSR to an eye tracking study will help understand what moments of TV content are more emotionally engaging for participants. GSR can also be added as a measure of the workload or stress level, for example in a study where the participants’ arousal level is expected to change over time. Finally, both GSR and pupil dilation reflect mechanisms of sympathetic activity, providing insights about the arousal level or cognitive load of a participant during a certain task.  

Emotional sweating

Sweating lies at the basis of the GSR measure. Sweating helps the body regulate its temperature. During a hot day or a workout, the body will start to sweat to maintain a constant body temperature. However, high temperatures are not the only reason why our sweat glands change their level of activity. The sweat glands are controlled by the sympathetic nervous system (SNS), a subdivision of the autonomic nervous system (ANS), responsible for the fight or flight response. Every time our body perceives a stimulus that could change our resting state, the SNS automatically activates a physiological response that includes an acceleration of the heart rate, a dilation of the pupil, and an increase in sweat gland activity. This autonomic response is triggered by any type of emotional reaction, such as surprise, fear or anger, or when we are under stress. The SNS regulates the physiological response according to the intensity of the emotion. That is, the more intense the emotion, the higher the physiological reaction triggered by the SNS.

Figure 2. GSR sensor schematics  

Any fluctuation in the GSR signal that has not been caused by changes in skin conductance are considered to be GSR artifacts. There are different sources of these artifacts. The electrodes may have been improperly fixated to the skin, they may be due to rapid-transient artifacts, or to temperature changes. 

Response time of GSR changes

The response time of a physiological signal is time it takes to change its characteristics as a consequence of an external event or stimulus. Some physiological signals have response times of mere milliseconds, e.g., a visual brain reaction can be measured with EEG after only 50ms of the visual event onset. This is considered a high time resolution because the EEG changes can be related with confidence to the stimulus that caused it. For a GSR signal, the response time is of the order of seconds after an event has occurred, which we consider a low time resolution. Thus, it is important to take into consideration the GSR time characteristics during the experimental design.  

When there is an emotional reaction to an external event (e.g., visual stimulus), the phasic or rapid component of the GSR signal increases its amplitude temporarily, which is known as skin conductance response (SCR). This will not happen instantaneously, but with a certain delay or latency after the emotional event occurred. SCR latency varies within and between individuals. Current literature takes into account this variability and suggests a latency window of an SCR that spans from 1 to 5 seconds after the event onset. In other words, an SCR in response to an emotional event will start between 1 second and 5 seconds after the event begins. 

The SCR latency window creates an uncertain time period. If several events that can cause an emotional response occur during this latency window, it will not be possible to know which event caused the SCR. Therefore, when designing a visual experiment that will use GSR to study SCR to specific events (known as ER-SCR), it is important to display the stimulus for enough time to make sure that an SCR can be associated with the stimulus of interest, and ensure that SCRs do not overlap. A common minimum stimulus duration time is around 10 seconds, with similar inter-stimulus-interval durations. In recent years, there has been some research that aims both to improve methodologies allowing for shorter inter-stimulus-intervals and to propose advanced analysis tools that can achieve a better SCR parametrization when SCRs overlap (e.g., Alexander et al., 2005; Benedek & Kaernbach, 2010).  

The tonic or slow component of the GSR signal will also change its amplitude over time due to general arousal level or stress. The GSR signal amplitude increases when we are under stress and decreases as we relax. Arousal level variations are also quite slow and happen over the course of tens of seconds to minutes. When using GSR to study general arousal level or stress, it is also important to take into consideration the tonic response time by designing tasks that are long enough to allow for GSR amplitude variations in response to the stress level that the subject is experiencing.

GSR artifacts  

Movement artifacts.

Electrodes that are not adequately fixated to the skin will move around, which affects the contact area between the electrode and the skin. This can generate sudden troughs and peaks in the GSR signal (see Figure 4), usually larger in amplitude and frequency than skin conductance responses (SCRs).

Figure 5. A GSR signal with sudden rises and falls caused by moving electrodes.  

A participant's sudden movements and pulling on the GSR electrode wires can also lead to movement artifacts. The signal fluctuation due to this artifact usually has amplitude and frequency components similar to a GSR signal. This type of movement artifact can be distinguished from GSR responses through visual inspection, as this type of artifact typically has a shorter rise and fall time than a rapid SCR (see Figure 5). If you find this type of artifact in your data, the best practice is to discard that portion of data.

Again, the best practice to avoid this type of artifacts is by placing the electrodes on the participant's non-dominant hand and by taping the electrode cables to the skin or clothes to minimize the chance of them being pulled. The participant should be instructed to avoid abrupt movements. If the experimental task involves hand movements or object manipulation, it may be a good idea to place the electrodes on other body parts that are known to produce a good GSR signal, like the feet or shoulder.  

High frequency noise

The level of conductance of the skin changes slowly, with a frequency of 1Hz or less. Therefore, any fluctuation that appears in the GSR signal at a higher frequency can be considered a GSR artifact (see Figure 6). The most common sources of high frequency noise are electrical noise at 50/60Hz and the precision error of the GSR sensor. 

High-frequency noise can be eliminated with post-processing tools that apply a noise reduction filter that removes the high frequency components of the GSR signal. Examples of filters that will remove high-frequency noise are  low-pass  filters and  moving-mean  filters.  

Figure 7. A comparison between a galvanic skin response (GSR) signal without (top) and with (bottom) noise reduction filter.

Rapid-transient artifact

Discrete and rapid changes can also appear in a GSR signal (see Figure 7). These rapid changes are usually much faster than skin conductance change and can have variable amplitude. A very fast electrode movement can cause this type of artifact.

Rapid-transient artifacts can be eliminated with post-processing tools by applying a noise reduction filter that removes the rapid frequency components of the GSR signal. The most common type of filter is a moving-median filter.  

Temperature changes

Body temperature changes will impact the GSR signal, with a slow GSR signal decrease as the body temperature changes. This is a physiological artifact generated by the thermoregulatory processes in our body that are not related to emotional arousal. If the main interest of research is the rapid changes of the GSR signal, this will not have a significant impact on the results. If the interest of research is focused on the GSR slow fluctuations, temperature changes over time may mask your results. To avoid temperature changes in your participant during the experiment, the room temperature and humidity should be regulated to a comfortable level and controlled across sessions and participants.  

GSR metrics in Tobii Pro Lab

GSR measures add valuable insights to your eye tracking experiment about the emotional state of a participant. Tobii Pro Lab offers a set of GSR metrics that quantify skin conductance responses (SCRs) and arousal levels during an experiment. The type of research question and experimental design will determine which GSR metrics are relevant for answering your research question. Tobii Pro Lab provides three GSR-related metrics: SCR count ,  event-related  SCR amplitude , and GSR average . A SCR is a temporary change in GSR signal amplitude that gives information on a participant's emotional state. The SCR count can be used to identify what specific moments in a dynamic stimulus, such as a commercial, causes an emotional response in a participant. A higher SCR count indicates a higher level of emotional arousal.  When a SCR happens between 1 to 5 seconds after an event, the SCR is classified as an event-related SCR (ER-SCR). The amplitude of the SCR gives an indication of the intensity of the emotional response towards an event. The ER-SCR can for example be used to learn whether certain stimuli (e.g., threatening stimuli) lead to a larger emotional response than other types of stimuli (e.g., neutral stimuli). It can also be used to test individual variation in response to certain stimuli, for example comparing high-anxiety participants' emotional response to fearful stimuli compared to the response of low-anxiety participants. When environmental conditions are kept constant, the slow fluctuations in the GSR signal (within the period of seconds to a period of minutes) reflect changes in the emotional arousal of a participant. The researcher can use the GSR average metric for different sections of the session to determine if a participant is getting stressed, frustrated or relaxed during the course of an experiment. Examples of where the GSR average metric is useful to get insights about general emotional arousal levels are:

• To evaluate stress level changes over different tasks that study aspects of human behavior (e.g. in a decision-making study)
• To get an indication of the frustration level and task difficulty (e.g. in a web usability study)

Besides these three metrics, the Data Export function of Tobii Pro Lab offers access to raw or filtered GSR data as well as information about the onset and peak time of all the SCRs in the data. This information can be used to provide additional metrics, such as all SCRs and their main parameters and data standardization calculations or ratio of non-specific SCR per participant (NS-SCR).  

GSR data filtering in Tobii Pro Lab

1. gsr data filtering.

Figure 9: Example of raw versus filtered GSR data in Tobii Pro Lab.  

2. Skin conductance response detection analysis

After the GSR data has been collected in Tobii Pro Lab, Tobii Pro Lab applies a SCR (skin conductance response) detection algorithm to identify SCRs in the GSR data, which follows the following steps:

• The GSR data is down sampled by an integer factor (only samples are deleted, no interpolation takes place). If the data is collected with the Shimmer3 GSR+, the down-sample factor is 8, which leads to a final sampling rate of approximately 15Hz.
• A standard peak detection method (trough-to-peak) is applied to the GSR data to identify all local maxima and minima of the GSR signal. All trough-to-peak pairs are classified as SCRs if their amplitude is higher than the minimum amplitude threshold of 0.03µS.
• The three main characteristics of each detected SCR are computed:
• SCR amplitude : Amplitude difference in GSR level between SCR onset and the SCR peak.
• SCR rise time : Time difference between SCR onset and peak.
• SCR half recovery time : Time difference between when the GSR level has recovered to 50% of the SCR amplitude and the peak time*.

3. ER-SCR classification

SCRs can be considered to be produced in response to a specific event (e.g., stimulus onset) when its onset falls within a specific time window after the event (Boucsein, 2012). In Tobii Pro Lab, all identified SCRs with their onset at 1s to 5s after a stimulus onset and custom time of interest (TOI) interval start will be classified as ER-SCRs.

For each ER-SCR, Tobii Pro Lab will compute (see Figure 10 for a visualization):

• Event : Name of the event that caused the ER-SCR.
• Latency : Time difference between the SCR onset time and the event time.

Additional notes on the classification of SCRs:

• There will always be a maximum of one ER-SCR for each event. If more than one SCR onset is found within the time window, the first SCR will be considered the ER-SCR.
• If no SCR onset is found within the time window of an event, the event will be considered as not having elicited an ER-SCR, which will be indicated in the GSR metrics.
• An SCR can be classified as an ER-SCR for more than one event. One example of this is when a stimulus is shown for less than 4 seconds. In this case, there will be two stimuli onset in periods shorter than the ER-SCR time window. Tobii Pro Lab will classify the SCR as ER-SCR for the two events. In the replay of individual recordings, this will be displayed as more than one blue marker on top of the ER-SCR peak.

Finally, due to the GSR signal characteristics, the following must be considered when working with GSR data:

• Data normalization : We advise to perform a transformation to GSR metrics so that the data fit a normal distribution. This way, parametric statistical analyses can be performed. The most common transformations are to compute the Log or square-root of the SCR amplitude, the Log of the GSR average, or the Log of ER-SCR magnitude + 1.
• Relative GSR metrics for between-participant designs : The GSR signal has large individual differences, with an identical SCR amplitude indicating a large emotional response in one participant, and a small response in another. This variation does not provide an issue in within-participant designs (in which a participant is exposed to all experimental conditions). However, in between-participant designs, where the GSR metrics are compared between different groups, it is important to use relative GSR values. The two most common approaches to compute a relative GSR value is by calculating the individual difference between the minimum and maximum GSR value and relating individual values to this range, or by using Z-scores. 

References and recommended reading

Emotional regulation, fear and threat, pupil and galvanic skin response, media research, related articles.

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• (108); 2016

Use of Galvanic Skin Responses, Salivary Biomarkers, and Self-reports to Assess Undergraduate Student Performance During a Laboratory Exam Activity

Idalis villanueva.

1 Department of Engineering Education, Utah State University

Maria Valladares

Wade goodridge.

Typically, self-reports are used in educational research to assess student response and performance to a classroom activity. Yet, addition of biological and physiological measures such as salivary biomarkers and galvanic skin responses are rarely included, limiting the wealth of information that can be obtained to better understand student performance. A laboratory protocol to study undergraduate students' responses to classroom events ( e.g. , exams) is presented. Participants were asked to complete a representative exam for their degree. Before and after the laboratory exam session, students completed an academic achievement emotions self-report and an interview that paralleled these questions when participants wore a galvanic skin sensor and salivary biomarkers were collected. Data collected from the three methods resulted in greater depth of information about students' performance when compared to the self-report. The work can expand educational research capabilities through more comprehensive methods for obtaining nearer to real-time student responses to an examination activity.

Introduction

In the area of academic achievement emotions, studies indicate that understanding of students' motivations could predict students' performance, achievement, and career plans 1 . Students' abilities to 'emotionally respond' to challenging course tasks 2 are pivotal to students' professional development. Yet, nearer to real-time responses related to academic achievement emotions are under-explored 3-6 . This paper presents a protocol to study ways to explore nearer real-time responses from students ( e.g ., physiological responses) when presented with representative classroom situations ( e.g ., test taking) using salivary biomarkers, galvanic skin responses, and self-reported surveys and interviews. While the work will not seek to establish connections between these salivary biomarkers, galvanic skin responses and self-reports, future work will aim to further explore the underlying mechanisms that associate each response.

Self-reporting of academic achievement emotions in the classroom can be used to assess affective, cognitive, motivational, physiological, and behavioral components that represent the human mind. Due to its cheap cost, easy dissemination and traceability, self-report surveys are highly used in classroom settings 7 . However, these have some disadvantages. For example, self-reports are limited to the representations of the conscious mind 8 , which can change the manner that individuals represent themselves. Also, language and semantics in self-reports may be understood differently between cultures and individuals 7 ; its meanings can change over time or represent something different in light of the situation that the participant is involved in 8 . Moreover, self-reporting in academic settings can be multifaceted, idiosyncratic and dependent on memory, social desirability, and individual beliefs 7, 9-11 . For example, participants' beliefs about professors' expectations and motives can affect how students respond and perform during classroom activities 7, 9-11 . As such, complementary methods based on nearer to real-time responses are needed to reduce sampling biases and subjectivity when using self-reports. This work will supplement self-reports with salivary biomarkers and galvanic skin responses to better understand the nearer real-time responses of students to classroom activities.

Sampling of salivary biomarkers has become popular in understanding physiological foundations of individuals' responses to various stressors that can impact cognitive abilities 9 . Psychological development of cognition is affected by hormones in many species, including human beings 7,12 . During sensitive periods of development, hormones are capable of making changes in the organization of the brain, which can have long-lasting effects on behavior 8 . Different aspects of cognition, for example, can be affected by hormones during different times of an individual's development. Spatial ability, which studies have shown can include gender differences 13-17 , is moderately enhanced by androgens ( e.g ., dehydroepiandrosterone-DHEA, testosterone) in prenatal development and then again throughout adulthood 18 . On the contrary, verbal abilities have been linked to enhancement of oestrogens ( e.g ., estradiol) and progesterones 18 . Physiological biomarkers of stress such as cortisol, are found in the hypothalamic-pituitary-adrenal axis in humans 12-16, 19-21 . When a situation is perceived as uncontrollable, cortisol levels elevate 19 and can result in differential responses in individuals. Recent work has begun to use hormones to study academic achievement emotions, although to this point it is very limited 20,22 .

Research in understanding psychophysiological responses that measure emotion via physiological arousal in education has used galvanic skin responses (GSR). GSR is a measure of microscopic amounts of sweat secreted from the skin and is related to the autonomic nervous system (ANS). When a person becomes nervous or anxious about a task, palms become sweaty. Therefore, emotional regulation and cognitive processes, among other brain functions, can influence the control of sweating. More activation of the system ( i.e ., high stress, cognitive load or strong emotional responses) results in more sweat secretion than low activation states ( i.e ., boredom, low cognitive load). As sweat secretion fluctuates, the electrical conductivity of the skin changes. Thus, GSR is widely considered as a proxy for quantifying stress level or cognitive load. GSR is typically measured by bands containing electrodes that come into contact with hands, wrist, or feet and is recently being used in classroom settings 22,23 due to its low cost and feasibility compared to available neuroimaging techniques 7 . The combination of galvanic skin responses with salivary biomarkers will allow for a more comprehensive assessment of student responses to classroom activities nearer to real-time.

The proposed protocol discussed here will serve to combine educational and physiological techniques to establish a methodology to help educational researchers understand student performance and response to classroom activities ( e.g ., exams). While the work will not focus on understanding fundamental connections between emotions and physiological and biological constructs, this protocol is a starting point to help researchers move in that direction. This protocol will cover methods to measure salivary biomarkers and galvanic skin responses during an exam activity and compare it against the information obtained from self-reports and interviews. For this work, an engineering exam and students were selected due to the difficult and complex nature of the discipline 1,6 and concepts, which may ignite both cognitive and emotional responses in the participants.

Procedures have been approved by the Institutional Review Board (IRB) at Utah State University for studies on human subjects. Care should be taken that IRB procedures are approved by the host institution and considerations regarding the protection of human subjects should take place prior, during, and after performance of any aspect of this protocol. As per IRB regulations, involvement of external parties or companies in the data collection and analysis processes must follow proper protocols to de-identify participant information and protect the confidential nature of the data.

1. Selection of Participants and Activities to Test

• Select student participants at the middle of the semester or 3 months after a desired course content was presented by the professor to diminish any short-term memory recollections from the participants.
• Exclude any participants from a laboratory study that parallels this work if the participant has a: (a) history of pre-determined condition ( e.g . arrhythmia) or metabolic disorder; (b) left-handedness or ambidextrous ability (this can interfere with physiological sampling); (c) psychological history (current or past) or history of behavioral or emotional disorder (this can skew the collection from the self-reports); (d) medical history for heart, metabolic, or cognitive disorders; (e) physical disability that would prevent participation in the laboratory sessions of the study; and (f) traumatic brain injury. Female participants wishing to be part of the hormonal study have additional restrictions explained in step 2.5.
• Recruit according to established Institutional Review Board (IRB) protocols by including detailed procedures and restrictions about protection of confidentiality. NOTE: If a company will have access to the data, (in this case salivary samples and galvanic skin response data were collected from third party companies) ensure that an agreement is in place for proper handling of data ( e.g ., time for refrigeration), sharing ( e.g ., security of server), and include a timeline to destroy the data ( e.g ., one year after publication of data). Include these guidelines in your IRB application and follow proper guidelines as required by the IRB organization within your institution.
• Select course activities that represent the complexity of knowledge and tasks that students need to perform in. NOTE: For this protocol, freshmen engineering students were selected due to the difficult and complex nature of the course content. The activities that were deemed representative were a combination of two types of engineering problems from two commonly used engineering exams: the Mental Cutting Plane Test (MCT) and the Purdue Spatial Visualization Test (PSVT-R). MCT looks at two-dimensional cut sections that corresponds to a three-dimensional object 24 while PSVT-R looks for three-dimensional rotation of an object 25 . Each were used to test for spatial performance and verbal memory for this student population 26, 27 .

2. Prior to the Laboratory Session

• Host an orientation for the volunteer participants at least 1 - 2 weeks prior to the laboratory session. Clarify all terms from the IRB informed consent. Perform a demonstration of the use and fitting of the galvanic skin sensor and proper data collection procedures for salivary hormone collection, according to the manufacturer protocols 28 . Explain the risks and benefits of the study.
• Establish a calendar that participants can enroll in. If participants are enrolling in the salivary biomarker piece of the study, be sure to establish times during the morning before breakfast as cortisol levels are lowest at this time of day and include any disclosures for enrolling in the allotted times (see step 2.5 for more information). NOTE: Ensure that all participants provide at least three available time slots for the study. Accommodate participants in a randomized fashion to minimize biases and provide more statistically valid results.
• Pre-fit the galvanic wrist sensor for each volunteer by ensuring that the sensor straps secure the participant's wrist during the orientation session. Enter the participant study ID code and the unique wrist sensor bar code provided by the supplier to ensure consistency for follow-up laboratory sessions if needed.
• Send a reminder to the participants of the procedures and restrictions for data collection and pre-conditions prior to the day of sampling, according to manufacturer protocols 28 . NOTE: Examples of procedures and restrictions can include: (a) no food, dietary or energetic products, or sugary drinks during diurnal collections or at least 1 hr prior to the study; (b) no water consumption 1 hr prior to data collection; (c) no teeth brushing or mouth rinses; (d) no chemical products ( e.g. , hand lotions, creams, chapsticks, perfumes, dyes) in the required contact areas ( e.g ., wrists, face, lips); (f) no hair products or styling; and (g) no physical activities ( e.g. , brisk walking, cycling, running, weights) 24 hr before the study.
• For female participants, collect salivary samples between 10 - 12 days after the first day of the participant's menstrual period to minimize hormonal fluctuations during salivary collection 28 . NOTE: During the stated time period, if female participants are taking any form of hormone-based treatment such as any birth control pills, intrauterine devices, creams or sprays (oral, topical, or vaginal), sublingual and troches, patches, films, injections, allow 12 - 36 hr to pass from the time of ingestion/application to allow the treatment effects to level off. The timeline required to collect salivary samples will vary by the biomarker and the specifications of the company's salivary kit. Galvanic skin response collection is done according to Section 3.2 for female participants. Male participant salivary collection is done according to Section 3.1.5.1 and galvanic skin response according to Section 3.2.

3. Day of Laboratory Session

NOTE: The following procedures are presented in recommended order of data collection under the assumption that 1 - 2 researchers are involved. However, some of these procedures could be run in parallel if more than 2 researchers are collaborating in the study.

• Provide participants with a checklist to outline physical activities exerted during the 24 hr period prior to the study ( e.g ., physical activity, food and drink consumption, use of lotions or hormone based products) as described in the manufacturer protocol 28 (see step 2.4 and 2.5). NOTE: If a participant has performed any or all of the activities from the checklist, re-assign the participant to meet at another day. If water consumption was the only restriction not met, ask the participant to stay an extended time in the study to allow an appropriate time, according to manufacturer guidelines, to pass (~ 1 hr) before salivary collection occurs.
• Ask the participants to fill out the health information checklist provided by the saliva assay kit 28 . Ensure that all salivary vials are pre-labelled and time stamped before and after the laboratory sessions. NOTE: Salivary cortisol has a reactivity of approximately 20 min 19,20 and as such, spit collection procedures should be done within this timeframe. Follow spit collection procedures according to step 3.1.5 and manufacturer guidelines 28 .
• Keep a copy of the health information checklist and shipping information for future record-keeping, tracking, and further analysis. Be sure to follow IRB protocols and procedures during storage of checklist items. Complete a timeline of the laboratory activities, personnel, and collection vials for each participant.
• Ensure that all participants and researchers handling salivary samples are wearing aseptic gloves at all times to minimize cross-contamination.
• Instruct participants to not touch the tip of the vial with the participant's lips or fingers as this can introduce contamination to the sample (spit vial method). To encourage salivary production, recommend to the participant to smell a citrus fruit such as a lemon or head tilt forward to speed up formation of saliva.
• Store all collected salivary samples -20 o C for up to 7 days if analysis of these samples will not occur immediately. Longer storage (up to 30 days) will require samples to be stored at -80 o C.
• To ship the frozen samples to a third party company, have a sealed foam box containing dry ice ready and an airtight and sealed copy of the health information sheet pre-filled by the participant. Make sure that participants place their unique study ID code in the identifier section of the sheet to prevent private information to be sent to the company.
• When ready, ship the vials to the company for analysis of biomarker for the Salivary Profile 1: Testosterone, Progesterone, DHEA, Cortisol, and Estradiol. Analysis of biomarkers was carried out by the manufacturer according to established protocols 28 . Place samples in an immunoassay plate reader and read the sample optical density at a wavelength of 450 nm. NOTE: All biomarkers require a solid-phase, competitive enzyme immunoassay. A fixed amount of the conjugated biomarker competes for the binding sites with an antibody that corresponds to each biomarker. After incubation, unbound components are washed away and an enzyme substrate solution is added, forming a color representative to the biomarker. For example, progesterone begins with a blue color and upon reacting with the enzyme becomes yellow.
• Clean the galvanic skin sensors with prepackaged sterile 70% alcohol wipes or a sterile gauze containing a small amount of 70% isopropanol to remove residues from prior participants. Clean the device before and after every data collection session or participant, whichever comes first.
• One hour before the study session, remind participants to clean and dry their hands. NOTE: Collection of salivary samples in combination with the galvanic skin response will require that collections time points are considered. For example, cortisol salivary collection should be collected within 20 min (step 3.1.2) while galvanic skin sensors need to be fitted and calibrated with 5 - 10 min as described in step 3.2.6.
• Place a new or clean sports wrist band in the non-dominant writing wrist of the participant before installing the galvanic skin response sensor. Allow the participant to wear the wrist band for 1 hr prior to collecting data. NOTE: The sports wrist band should be pre-labelled according to the unique wrist ID to avoid cross-contamination between participants
• After 1 hr, remove the sport wrist band and place the galvanic skin sensor. Ensure that the galvanic skin sensor touches the median nerve of the wrist to ensure proper collection of pulse and heart rates. Unite the bands together in the sensor to ensure a tight fit on the wrist.
• Press the galvanic skin sensor indicator light. Wait until the light turns from red to green to white; a white color indicates that data collection has started.
• Ask the participant to wear the galvanic wrist sensor for a set period of time (5 - 10 min) with no physical movement from the non-dominating wrist to calibrate and collect baseline tonic data. NOTE: A baseline data will be found when the galvanic skin response data levels off and no spikes or noise is longer visible. Check the manufacturer software using the assigned account by the manufacturer. Open a session and verify that data is being collected 29 .
• Start a slide presentation containing representative and time stamped problem sets for each of the exams activities described in section 1.5. Ask the participant to record the times after completing each slide to allow for timestamps between the collected GSR data and the events to be compared.
• Periodically check that the galvanic skin sensor lights are white and verify that data is being collected. NOTE: Sampling rate of the sensors presented in this work was based on manufacturer specifications and capabilities (rate of 8 Hz with a low electrical current of 1100 mAh).Galvanic response through electrodermal activity (EDA) was reported in microSiemens (µS) as tonic (baseline responses to an exam event or self-report/interview question) and phasic (acute, immediate response to an exam event or self-report/interview question, above a certain µS threshold).
• Have handy a replacement battery and sensor, in case data collection problems occur during the session. At the end of the session, press the indicator light until it is turned off. Carefully remove the wrist sensor and wipe it with alcohol.
• Retrieve the data from the manufacturer software 29 . Log in to the account and click on Sessions. Select the date of the study and click on the Download tab. Download the data in .csv file for easy use.
• Track timelines of the events in the study. Download the data in the wrist sensor software session. Download data as a UNIX epoch time, which is the number of seconds that has elapsed since January 1, 1970 (not counting leap seconds). Convert the UNIX time to a GMT time zone if timelines need to be tracked in the data using an open source timestamp converter 30 . To convert this time, simply convert the time in the data sheet using this conversion (1 year = 365.24 days = 31556926 sec).
• Retrieve electrodermal data in wrist sensor software session. Click View on any of the desired sessions. Present the data as real-time or select by a set period of time by the researcher.
• Before and after the slides, provide a pre- and post- survey.During the second collection point (end of the exam), collect the final salivary sample and then provide the self-report while collecting EDA data. Record all time points. NOTE: This study used a modified Topics in Emotion scale developed by Broughton and colleagues 31 .
• While wearing the galvanic skin sensor, ask the participants questions that paralleled the self-report. NOTE: Keep in mind that timelines need to be considered if you are collecting salivary samples as indicated in step 3.1.2 and 3.3.3.
• As possible, record the date and time for cross-checking of GSR data and its alignment with the timing of the self-reported responses in a laboratory notebook. In addition, include instructions in the slide show presentation explaining to the participants to annotate the time after completing the required instructions after each slide to enable cross-comparison of timed events with the GSR data.
• Ensure that the computer based software has consistent instructions and that each slide is clearly labelled. If keystroke setups are needed for the study, indicate in the slide instructions what keystroke should be pressed in each slide.
• After collecting all the information, remove the wrist sensor and turn off the sensor data in reverse order to step 3.2.5. Guide the participants to a designated room offering food, beverage, drinks, and provide receipts for a future monetary compensation (if it was stated in the IRB consent form) for participation in the study.
• Follow-up the activity with an emailed notification of gratitude for participation and include available timeslots for discussion of the results with the participants.

Representative Results

This section illustrates representative examples of results that can be obtained from each measure, including the self-report. The intent of the figures is to present the utility of adding measures such as salivary biomarkers ( Figure 1 ) and galvanic skin responses ( Figure 2 ) to self-reports ( Figure 3 ) in order to gain a greater spectrum of information from a classroom event ( e.g ., exams). For triangulation of self-reports with a specified measure ( e.g ., galvanic skin response), additional techniques such as interviews can provide a useful comparison method ( Figure 3 ). The results in Figure 1 show that participants' biological responses differed by gender when comparing hormonal levels between the beginning and end of the exam. Hormones such as estradiol levels increased in males while progesterone levels increased in females (p  <0.05). High estradiol levels has been tied to brain activation of verbal performance tasks 32 while progesterone is related to spatial abilities such as mental rotation of an object 12-16, .Spatial activities were upregulated in females through increased testosterone (p <0.05) whereas DHEA showed no significant differences due to gender (p = 0.39). DHEA and testosterone has been linked to increased visual-spatial performance in adults 12-16, 34 . Cortisol levels for females and males did not change pre- and post- the laboratory session (p = 0.41) possibly due to exceeding short half-life of cortisol (~45 min) during the second salivary collection 19,20,32 .These results show that student performance is differential, in this case by gender, and that hormonal biomarkers can be a useful tool in identifying these differences.

Measurement of emotion via physiological arousal using galvanic skin response, demonstrated differential responses unrelated to the type of exam (p >0.05) but showed instances of cognitive engagement (sustained tonic levels) during the test-taking experience for all participants as seen by the GSR tonic peaks compared to the baseline (initial rest phase). A representative GSR data set is included in Figure 2 . A sustained physiological arousal was found during the final data collection session where self-report and interview responses were collected. Self-report responses completed by the participants as they wore the galvanic skin sensor ( Figure 3A ) 31,36 suggests no perceived differences in emotions by the participant to the exam (p = 0.055). However, when students were ask to response to the interview questions that paralleled the self-report, physiological arousals were found as seen by the increased tonic responses ( Figure 3B ). This result suggest that emotional activation may require cognitive and verbalized recollection of events.

The data demonstrates that verbal and spatial activation is differential in participants despite obtaining equal scores in their exams (data not shown). Physiological arousals were dependent on the mental recollection by the participants when performing a sequentially harder exam problem (progression from MCT to PSVT-R). Furthermore, use of written self-reports did not demonstrate a significant physiological response or a self-reported emotionally significant difference by the participants. When asked to verbalize the self-reported items, emotional arousals were found in the participants. Together, the data points to the different mental resources used by students when performing an exam. It highlights the importance of allowing students to cognitively recollect their thoughts as they sequentially perform increasingly difficult problems in and exam. Finally, the study results highlight how self-report alone are not sufficient to fully represent the spectrum of responses from students. Thus, inclusion of biological and physiological measures to self-reports and interviews can assist educational researchers to acquire a more robust data set that can help explain the complex performance of students in an educational setting.

Figure 1. Hormonal Activities for Female and Male Engineering Student Participants Before and After a Laboratory Study Session. Percent change of hormone levels before and after the laboratory session 36 indicates that females increased in both progesterone and testosterone and decreased in estradiol levels when compared to males before and after the exam (paired T-test p <0.05 for estradiol; paired T-test p <0.05 for progesterone; paired T-test p <0.05 for testosterone). Cortisol and DHEA, measures of stress 19,20 and spatial ability 12-16,33 , did not show significant changes (p = 0.39 and p = 0.42, respectively), despite obtaining equal scores in their exams (data not shown). Please click here to view a larger version of this figure.

Figure 2. Galvanic Skin Response of an Engineering Student Performance during a Laboratory Study Session.  Galvanic skin tonic response in µS collected for an engineering student undergoing a series of representative activities in a laboratory study session. The initial time represents a resting phase to establish a baseline. Following this, the student completed representative engineering problems for the exam. Physiological arousals were dependent on the mental recollection by the participants when performing a sequentially harder exam problem (progression from MCT to PSVT-R). Afterwards, the student completed a written self-reflective 10-item survey, which showed no effect followed by an interview (containing parallel questions to the self-report) where an emotional arousal was seen. Please click here to view a larger version of this figure.

Figure 3. Representative Side-by-side Comparison of Self-reported Responses from Emotion Survey and Interview.  Comparison of galvanic skin response of engineering student self-reported responses ( A ) and interview ( B ). Panel A shows descriptive statistics (n = 7) in which a paired sample T-test analysis showed no statistically significant differences (p = 0.055) between the pre- and post- self-report surveys. Panel B demonstrates GSR increase in arousal during the second self-report (step 13 - 14) as well as during the interviews (15a - 16). Arousal fluctuations were greater during the interview, compared to the surveys. Please click here to view a larger version of this figure.

This protocol describes the integration of self-report surveys and inquiries, salivary biomarkers, and galvanic skin responses to study individual differences in classroom activities during a laboratory session. This protocol has many advantages for researchers seeking to identify academic achievement emotions, emotional regulation, and affective responses to different activities in an instructional setting, especially during assessment periods ( e.g ., exams). Whereas traditionally, self-reports and academic grades have been used to understand how students develop competencies in the classroom and/or engagement to a course, our methods can more comprehensively represent nearer to real-time responses of students during academic activities.

For success of this protocol, it is crucial that salivary biomarkers and galvanic skin responses are collected diurnally, that the participants are aware of the behavioral and biological restrictions of this study ( e.g ., health conditions), and that continual follow-up with the participants is conducted. Also, care should be taken in the handling of the samples as this should be done in aseptic conditions. Some limitations of the study include the allowable time frame ( e.g ., 10 - 12 days after the menstrual period) for salivary data collection for females as well as difficulty in precisely timing the events with the real-time galvanic skin response collection ( e.g. , salivary cortisol may require a 20 min collection time while galvanic skin sensor calibration requires 5 min). As such, data collection procedures should consider proper time stamping of sections and problems that participants complete during the laboratory session to ensure proper statistical data analysis and triangulation. Finally, due to the delicate nature of the self-reported emotions, emotional responses, and biological and physiological data is attained and assessed, protocols should follow the Institutional Review Board for Human Subjects policies and procedures.

With technological developments in non-intrusive wearable technologies and biological markers, methodologies can be combined to triangulate complex undergraduate students' experiences and performance to academic tasks. This method expands the potential of self-reported surveys and physiological information that has normally not been combined to understand nearer to real-time emotion and cognitive responses to different classroom activities.

One direction for this protocol is to incorporate the methods in a larger setting ( e.g ., classroom) in real-life contexts. For this, additional considerations on time, coordination on the use of resources and software, management of hormone kit and GSR wrist sensors usage will need to be considered as well as important mechanisms between the constructs.

Disclosures

None of the authors have competing interests or conflicting interests.

Acknowledgments

Maria Manuela Valladares is supported by a Utah State University Research Catalyst SEED Grant attained from Idalis Villanueva.

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