In this article, we will explore the fundamentals of GSR, how it works, and its applications in psychological research. We will discuss the advantages and limitations of this method and provide examples of its use in various contexts. By the end of this article, readers will have a firm understanding of GSR and its value as a research tool in the field of human behavior research, and psychology.
Galvanic Skin Response (GSR) is a physiological measure that has been used in psychological research for over a century. GSR measures the electrical conductance of the skin, which changes in response to emotional arousal and other psychological processes. This non-invasive method has proven to be a useful tool in understanding the mechanisms behind emotional responses and assessing psychological states.
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The galvanic skin response (GSR, which falls under the umbrella term of electrodermal activity, or EDA) refers to changes in sweat gland activity that are reflective of the intensity of our emotional state, otherwise known as emotional arousal.
Our level of emotional arousal changes in response to the environment we’re in – if something is scary, threatening, joyful, or otherwise emotionally relevant, then the subsequent change in emotional response that we experience also increases eccrine sweat gland activity. Research has shown how this is linked to emotional arousal [1, 2, 3].
It is noteworthy that both positive (“happy” or “joyful”) and negative (“threatening” or “saddening”) stimuli can result in an increase in arousal – and in an increase in skin conductance. The GSR signal is therefore not representative of the type of emotion, but the intensity of it.
The Background of GSR signals
Vigouroux was the first researcher [4] to uncover a link between mental state and GSR activity, finding an association with the level of sedation in patients and skin resistance [1, 5]. This connection of emotional response to GSR signal has been explored in thousands of articles in the 120+ years since this seminal finding [review article].
While sweat secretion plays a major role for thermoregulation and sensory discrimination, changes in skin conductance are also triggered robustly by emotional stimulation [1]: the higher the arousal, the higher the skin conductance.
The amount of sweat glands varies across the human body but is the highest in hand and foot regions (200-600 sweat glands per cm2 [6]), where the GSR signal is typically collected from [7].
Skin conductance is not under conscious control. Instead, it is modulated autonomously by sympathetic activity which drives aspects of human behavior, as well as cognitive and emotional states [3]. Skin conductance, therefore, offers direct insights into autonomous emotional regulation.
It can be used as an additional source of insight to validate self-reports, surveys, or interviews of participants within a study.
What you need to know about GSR sensors
As GSR measurements work by detecting the changes in electrical (ionic) activity resulting from changes in sweat gland activity, the electrodes must be sensitive to these changes, and able to transmit that information to the recording device.
Most modern GSR electrodes have an Ag/AgCl (silver-chloride) contact point with the skin. Ag/AgCl electrodes are used as they are cheap, robust, safe for human contact, and of course are able to accurately transmit the signal from the ionic activity.
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Some electrodes also come prepackaged with ionic gel that can increase the signal fidelity, or ionic gel can be applied to achieve the same effect. Either way, the signal is sent through the electrode, to the wire (usually lead) that passes the information to the GSR device.
From here the data is either stored within the device to be later uploaded, is transmitted wirelessly to a computer system, or the signal is sent through a further wired connection to a computer. Different GSR sensors allow different means of transmission, and the choice of each will depend on the kind of research you’re carrying out.
Skin conductance is captured using skin electrodes which are easy to apply. Data is acquired with sampling rates between 1 – 10 Hz and is measured in units of micro-Siemens (μS).
GSR signals explained
The time course of the signal is considered to be the result of two additive processes: a tonic base level driver, which fluctuates very slowly (seconds to minutes), and a faster-varying phasic component (fluctuating within seconds).
Changes in phasic activity can be identified in the continuous data stream as these bursts have a steep incline to a distinctive peak and a slow decline relative to the baseline level.
Researchers focus on the latency and amplitudes of the phasic bursts with respect to stimulus onset when investigating GSR signal changes in response to sensory stimuli (images, videos, sounds).
When there are significant changes in GSR activity in response to a stimulus, it is referred to as an Event-Related Skin Conductance Response (ER-SCR). These responses, otherwise known as GSR peaks, can provide information about emotional arousal to stimuli.
Other peaks in GSR activity that are not related to the presentation of a stimulus are referred to as Non-Stimulus-locked Skin Conductance Responses (NS-SCR).
By using the skin conductance values, or the number of GSR peaks, it’s possible to add quantitative data to studies of emotional arousal. With more data at hand, it’s easier to uncover new findings and make new discoveries about human behavior.
If you’d like to learn more about how to use GSR in your research, download our free guide below that takes you through everything you need to know.
What You Need For Galvanic Skin Response Test
Galvanic Skin Response tests, often synonymous with measuring emotional arousal or stress levels, or a combination of the two, have become an indispensable tool in a myriad of very diverse fields ranging from psychology to market research. For those keen on implementing GSR tests, it’s essential to be well-acquainted with the primary components involved.
GSR sensor or electrodes
The foundation of any GSR test lies in the quality and efficiency of its sensors or electrodes. These are responsible for detecting tiny changes in the skin’s electrical conductance, resulting from sweat gland activity linked to emotional states.
- Material & Design: Typically made of silver or silver-chloride, the sensors ensure efficient conductivity and minimal interference. Their design often allows for easy attachment to the fingers or the palm, the most common regions for GSR measurements.
- Placement: Accurate readings necessitate proper placement. For most tests, sensors are placed on the index and ring fingers, as these areas are most sensitive to sweat gland activity changes.
- Maintenance: It’s vital to keep the electrodes clean and free of contaminants to ensure accurate readings over time.
Data acquisition device
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Once the electrodes detect a change, this data needs to be captured and relayed for analysis. Enter the data acquisition device.
- Connection: This device connects directly to the GSR sensors, often via wired connections, though wireless options are also available.
- Amplification: Given that the changes in skin conductance can be minute, the device amplifies the signal, making it discernible for further analysis.
- Portability: Depending on the nature of the study, researchers might opt for portable devices, especially if real-world, dynamic environments are part of the testing setup.
- Software to record and analyze the skin conductance responses
After data acquisition, the software plays a pivotal role in both recording the raw data and aiding in its interpretation.
- User Interface: The best software offers a user-friendly interface, allowing researchers to monitor real-time data and ensuring everything is functioning as intended.
- Data Storage: Efficient data storage solutions enable easy retrieval and analysis of historical data, crucial for longitudinal studies.
- Analytical Tools: Modern GSR software not only records but also provides tools for data analysis. This includes distinguishing between tonic (baseline) and phasic (reactive) skin conductance levels, identifying peaks, and correlating them with external events or stimuli.
- Integration: Often, GSR tests are part of a larger set of biometric tests. Integration capabilities allow the software to work seamlessly with other systems, offering a comprehensive view of a subject’s physiological responses.
If you are looking to conduct GSR studies or want to integrate into your research flow, then we invite you to reach out to our expert team who is ready to guide you and make recommendations to your study setup or research needs. You can write to us here.
Freqently Asked Questions
What are the applications of Galvanic Skin Response?
Galvanic Skin Response (GSR) primarily measures emotional arousal and physiological responses. Its applications span across various fields such as psychology, where it’s used to study emotional reactions, market research for gauging consumer reactions to advertisements, and even in lie detector tests to assess the truthfulness of responses.
Are GSR tests used in clinical settings?
Yes, GSR tests have found their place in clinical settings. They are employed in therapeutic settings to monitor stress and anxiety levels, aiding therapists in gauging a patient’s response to particular stimuli or situations, and in the diagnosis and treatment of certain disorders like hyperhidrosis (excessive sweating).
What are examples of galvanic skin response?
Galvanic skin response is the skin’s varying conductivity due to emotional stimuli. Examples include a sudden increase in skin conductance when an individual is startled or stressed, or a decrease in skin conductance as someone relaxes after a period of anxiety. In a practical context, during a lie detector test, when a person feels nervous about a question, there might be a spike in their GSR, indicating heightened emotional arousal.
References
[1] Boucsein, W. (2012). Electrodermal Activity. New York, Berlin: Springer, 2nd edition
[2] Salimpoor, V.N., Benovoy, M., Longo, G., Cooperstock, J.R. & Zatorre, R.J. (2009). The rewarding aspects of music listening are related to degree of emotional arousal. PLoS ONE 4, e7487
[3] Critchley, H. D. (2002). Electrodermal responses: What happens in the brain. Neuroscientist, 8, 132-142
[4] Newman, E., Blanton, R., 1968. The early history of electrodermal research. Psychophysiology 6, 453-475
[5] Vigouroux, R, De la resistance Electrique comme signe clinique, Progres Medicate, 1879, No. 7, 336
[6] Gray, Henry (1918). “The Organs of the Senses and the Common Integument”. Anatomy of the Human Body (20th ed.). Philadelphia: Lea & Febiger
[7] van Dooren, M., de Vries, J. J. G. G.-J. & Janssen, J. H. (2012). Emotional sweating across the body: Comparing 16 different skin conductance measurement locations. Physiol. & Behav. 106, 298-304
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