Electrodermal activity

Electrodermal activity (EDA) is the property of the human body that causes continuous variation in the electrical characteristics of the skin. Historically, EDA has also been known as skin conductance, galvanic skin response (GSR), electrodermal response (EDR), psychogalvanic reflex (PGR), skin conductance response (SCR), sympathetic skin response (SSR) and skin conductance level (SCL). The long history of research into the active and passive electrical properties of the skin by a variety of disciplines has resulted in an excess of names, now standardized to electrodermal activity (EDA).[1][2][3]
The traditional theory of EDA holds that skin resistance varies with the state of sweat glands in the skin. Sweating is controlled by the sympathetic nervous system,[4] and skin conductance is an indication of psychological or physiological arousal. If the sympathetic branch of the autonomic nervous system is highly aroused, then sweat glands activity also increases, which in turn increases skin conductivity. In this way, skin conductivity can be a measure of emotional and sympathetic responses.[5] But the theory associating sweat and EDA was already debated decades ago since individuals without sweat glands have an EDA signal : ""The source of the skin potential is presumed to be the sweat glands and the epidermis, although it is present in subjects with congenital absence of sweat glands ... this is not a test of “sweat” function, it is often included in this category as a measure of sudomotor activity".[6]". This debate is ongoing since more recent technology (see Electrochemical skin conductance) demonstrated a real measure of sweat conductivity with several medical applications.[7] A good way to differentiate both is to look at measures values and type :
- EDA is a continuous measurement (signal curve with time) given in μS with value mostly <5
- while ESC values ranges from 0 to 100 μS with values under 10 being extremely low and rare. A value of 0 in the case of ESC could be theorically a single point EDA when sweat is totally absent.[8]
More research is needed and inclusion of additional phenomena (resistance, potential, impedance, Electrochemical skin conductance, and admittance, sometimes responsive and sometimes apparently spontaneous) suggest that EDA is more complex than it seems. There is a knowledge limitation, as wearable brands have included an EDA measure as a feature : "This aspect leads to the conclusion that the reliability of consumer wearables must be further investigated, especially by combining raw data collection with specific preprocessing techniques".[9]
History
In 1849, Dubois-Reymond in Germany first observed that human skin was electrically active. He immersed the limbs of his subjects in a zinc sulfate solution and found that electric current flowed between a limb with muscles contracted and one that was relaxed. He therefore attributed his EDA observations to muscular phenomena.[10] Thirty years later, in 1878 in Switzerland, Hermann and Luchsinger demonstrated a connection between EDA and sweat glands. Hermann later demonstrated that the electrical effect was strongest in the palms of the hands, suggesting that sweat was an important factor.[11]
Vigouroux (France, 1879), working with emotionally distressed patients, was the first researcher to relate EDA to psychological activity. In 1888, the French neurologist Féré demonstrated that skin resistance activity could be changed by emotional stimulation and that activity could be inhibited by drugs.[11]
In 1889 in Russia,
The scientific study of EDA began in the early 1900s. One of the first references to the use of EDA instruments in
The controversial Austrian psychoanalyst Wilhelm Reich also studied EDA in his experiments at the Psychological Institute at the University of Oslo, in 1935 and 1936, to confirm the existence of a bio-electrical charge behind his concept of vegetative, pleasurable "streamings".[20]
By 1972, more than 1500 articles on electrodermal activity had been published in professional publications, and today EDA is regarded as the most popular method for investigating human
Description
Skin conductance is not under conscious control. Instead, it is modulated autonomously by sympathetic activity which drives human behavior, cognitive and emotional states on a subconscious level. Skin conductance, therefore, offers direct insights into autonomous emotional regulation.[23]
Human extremities, including fingers, palms, and soles of feet display different bio-electrical phenomena. They can be detected with an EDA meter, a device that displays the change in electrical conductance between two points over time. The two current paths are along the surface of the skin and through the body. Active measuring involves sending a small amount of current through the body.[citation needed]
Some studies include the human skin's response to alternating current, including recently deceased bodies.[24]
Physiological basis
There is a relationship between emotional arousal and sympathetic activity, although the electrical change alone does not identify which specific emotion is being elicited. These autonomic sympathetic changes alter sweat and blood flow, which in turn affects GSR and GSP (Galvanic skin potential). The amount of sweat glands varies across the human body, being highest in hand and foot regions (200–600 sweat glands per cm2).[23] The response of the skin and muscle tissue to external and internal stimuli can cause the conductance to vary by several microsiemens. A correctly calibrated device can record and display the subtle changes.[25]
The combined changes between electrodermal resistance and electrodermal potential make up electrodermal activity. Galvanic skin resistance (GSR) is an older term that refers to the recorded electrical resistance between two electrodes when a very weak current is steadily passed between them. The electrodes are normally placed about an inch apart, and the resistance recorded varies according to the emotional state of the subject. Galvanic skin potential (GSP) refers to the voltage measured between two electrodes without any externally applied current. It is measured by connecting the electrodes to a voltage amplifier. This voltage also varies with the emotional state of the subject.[25]
Examples
A painful stimulus such as a pinprick elicits a sympathetic response by the sweat glands, increasing secretion. Although this increase is generally very small, sweat contains water and electrolytes, which increase electrical conductivity, thus lowering the electrical resistance of the skin. These changes in turn affect GSR. Another common manifestation is the vasodilation (dilation) of blood vessels in the face, referred to as blushing, as well as increased sweating that occurs when one is embarrassed.[25]
EDA is highly responsive to emotions in some people. Fear, anger, startled response, orienting response, and sexual feelings are among the reactions that may be reflected in EDA. These responses are utilized as part of the polygraph or lie detector test.[citation needed]
EDA in regular subjects differs according to feelings of being treated fairly or unfairly, but
Different units of EDA
EDA reflects both slow varying tonic sympathetic activity and fast varying phasic sympathetic activity. Tonic activity can be expressed in units of electrodermal level (EDL or SCL), while phasic activity is expressed in units of electrodermal responses (EDR or SCR).[27]
Phasic changes (EDR) are short-lasting changes in EDA that appear as a response to a distinct stimulus. EDRs can also appear spontaneously without an observable external stimulus. These types of EDRs are referred to as "nonspecific EDR" (NS.EDR).[28] The phasic EDR is useful when investigating multifaceted attentional processes.[29]
Tonic changes (EDL) are based on the phasic parameters. The spontaneous fluctuations of nonspecific EDR can be used to evaluate tonic EDA. More specifically by using the frequency of "nonspecific EDR" as an index of EDA during a specific time period, e. g. 30–60 seconds. Tonic EDA is considered useful in investigations of general arousal and alertness.[27]
Uses
EDA is a common measure of autonomic nervous system activity, with a long history of being used in psychological research.
EDA has also been studied as a method of pain assessment in premature born infants.[35]
Often, EDA monitoring is combined with the recording of heart rate, respiratory rate, and blood pressure, because they are all autonomically dependent variables. EDA measurement is one component of modern polygraph devices, which are often used as lie detectors.[25]
The E-meter used by the Church of Scientology as part of its practice of "auditing" and "security checking", is a custom EDA measurement device.[36]
Possible problems
External factors such as temperature and humidity affect EDA measurements, which can lead to inconsistent results. Internal factors such as medications and hydration can also change EDA measurements, demonstrating inconsistency with the same stimulus level. Also, the classic understanding has treated EDA as if it represented one homogeneous change in arousal across the body, but in fact different locations of its measurement can lead to different responses; for example, the responses on the left and right wrists are driven by different regions of the brain, providing multiple sources of arousal; thus, the EDA measured in different places on the body varies not only with different sweat gland density but also with different underlying sources of arousal.[37] Lastly, electrodermal responses are delayed 1–3 seconds. These show the complexity of determining the relationship between EDA and sympathetic activity.[25] The skill of the operator may be a significant factor in the successful application of the tool.[38]
See also
Notes
- ISBN 978-1-461-41126-0. Retrieved 20 October 2015.
- S2CID 146232135. Retrieved 2015-04-15.
Electrodermal activity (EDA) is now the preferred term for changes in electrical conductance of the skin, including phasic changes that have been referred to as galvanic skin responses (GSR)
- ISBN 9781475750935.
- ISBN 978-0-13-061567-1.
- ISBN 978-0-205-23939-9.
- PMID 18989618.
- PMID 39529803.
- PMID 39529803.
- PMID 37447697.
- ISBN 9781461411260. Retrieved 16 April 2015.
- ^ ISBN 9781461411260. Retrieved 16 April 2015.
- ISBN 978-161-330001-5. Retrieved 28 February 2017.
- ISBN 9780863775420. Page 33.
- ^ Daniels, Victor. "Notes on Carl Gustav Jung". Sonoma State University. Retrieved 4 April 2015.
By 1906 [Jung] was using GSR and breath measurement to note changes in respiration and skin resistance to emotionally charged worlds. Found that indicators cluster around stimulus words which indicate the nature of the subject's complexes...Much later L. Ron Hubbard used this approach in Scientology's "auditing," using the "e-meter" (a galvanic skin response indicator) to discern the presence of complexes.
- ^ The Biofeedback Monitor Archived 2008-09-15 at the Wayback Machine
- ^ "You can learn control of how your skin talks". San Bernardino, California: The San Bernardino County Sun. The San Bernardino County Sun. October 11, 1977. p. 12. Retrieved 8 April 2015.
Current research using the skin's electrical activity as a communications medium between patient and therapist looks promising in such stress problems as drug abuse, alcoholism, neuroses and other tension states.
- ^ Binswanger, L. (1919). "XII". In Jung, Carl (ed.). Studies in Word-Association. New York, NY: Moffat, Yard & company. pp. 446 et seq. Retrieved 30 March 2015.
- ^ Brown, Barbara (November 9, 1977). "Skin Talks -- And It May Not Be Saying What You Want To". Pocatello, Idaho: Field Enterprises, Inc. Idaho State Journal. p. 32. Retrieved 8 April 2015.
- ^ Mitchell, Gregory. "Carl Jung & Jungian Analytical Psychology". Mind Development Courses. Retrieved 9 April 2015.
- ^ Reich, W. "Experimentelle Ergebnisse ueber die electrische Funktion von Sexualitat und Angst" (Sexpolverlag, Copenhagen, 1937). Translated as "Experimental investigation of the electrical function of sexuality and anxiety" in Journal of Orgonomy, Vol. 3, No. 1-2, 1969.
- ISBN 9781461411260. Retrieved 10 April 2015.
- .
- ^ a b "What is GSR". iMotions A/S. Retrieved 18 August 2017.
- S2CID 13563354.
- ^ a b c d e Pflanzer, Richard. "Galvanic Skin Response and the Polygraph" (PDF). BIOPAC Systems, Inc. Archived from the original (PDF) on 18 December 2014. Retrieved 18 August 2017.
- ^ Oshumi, T., Ohira, H. "The positive side of psychopathy: Emotional detachment in psychopathy and rational decision-making in the ultimatum game". Personality and Individual Differences 49, 2010, pp. 451-456
- ^ ISBN 978-1-4614-1125-3.
- S2CID 17713243.
- OCLC 166506595. Retrieved February 22, 2024.
- ISBN 978-1-606-23040-4. Retrieved October 20, 2015.
- S2CID 146232135. Retrieved 27 April 2015.
- ^ Alterman, Ben. "Services Provided". Retrieved 28 August 2015.
- S2CID 31596383.
- S2CID 236035129.
- PMID 21764228.
- ISBN 978-0-07-162392-6.
- S2CID 10550306.
- ISBN 9780965579421.
References
- Conesa J (1995). "Electrodermal palmar asymmetry and nostril dominance". Perceptual and Motor Skills. 80 (1): 211–216. S2CID 31812398.
- Carlson, Neil (2013). Physiology of Behavior. New Jersey: Pearson Education, Inc. ISBN 978-0-205-23939-9.
- Figner, B., & Murphy, R. O. (2010). Using skin conductance in judgment and decision making research. A Handbook of Process Tracing Methods for Decision Research: A Critical Review and User's Guide, 163–84.
- Pflanzer, Richard. "Galvanic Skin Response and the Polygraph". BIOPAC Systems, Inc. Retrieved 5 May 2013.
- Nagai, Y.; S2CID 23077324.
- Loggia, M. L.; Juneau, M. N.; Bushnell, M. C. (2011). "Autonomic responses to heat pain: Heart rate, skin conductance, and their relation to verbal ratings and stimulus intensity". Pain. 152 (3): 592–598. S2CID 15779956.