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Galvanic skin response (GSR), also known as electrodermal response (EDR), psychogalvanic reflex (PGR), or skin conductance response (SCR), is a method of measuring the electrical resistance of the skin. There has been a long history of electrodermal activity research, most of it dealing with spontaneous fluctuations. Most investigators accept the phenomenon without understanding exactly what it means. There is a relationship between sympathetic activity and emotional arousal, although one cannot identify the specific emotion being elicited. The GSR is highly sensitive to emotions in some people. Fear, anger, startle response, orienting response and sexual feelings are all among the emotions which may produce similar GSR responses.
Physiological Basis[edit | edit source]
The combined changes between galvanic skin resistance and galvanic skin potential make up the galvanic skin response. Galvanic skin resistance(GSR) 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 in accordance with the emotional state of the subject. Galvanic skin potential(GSP) refers to the voltage measured between two electrodes without any externally applied current. This is conducted by connecting the electrodes to a voltage amplifier. Similarly, this voltage varies with the emotional state of the subject.
Due to the response of the skin and muscle tissue to external and internal stimuli, the conductance can vary by several microsiemens. When correctly calibrated, the device can measure these subtle differences. There is a relationship between sympathetic activity and emotional arousal, although one cannot identify which specific emotion is being elicited. These autonomic sympathetic changes alter sweating and blood flow, which in turn affects GSR and GSP.
Examples[edit | edit source]
- A painful stimulus, such as a pinprick, will elicit a sympathetic response to the sweat glands increasing secretion. Although this increase in sweat is generally very small, sweat contains water and electrolytes which increase electrical conductivity, thus lowering the electrical resistance of the skin. These changes will in turn affect the GSR.
- Another common example is the vasodilation of blood vessels in the face, referred to as blushing, as well as increased sweating that occurs when one is embarrassed.
The SCR(skin conductance response) is highly sensitive to emotions in some people. Fear, anger, startle response, orienting response and sexual feelings are all among the reactions which may produce similar skin conductance responses. These reactions are utilized as part of the polygraph or lie detector.
Skin Conductance Response in regular subjects differs when given fair and unfair offers, respectively. However, psychopaths have been shown to have no difference in skin conductance between fair and unfair offers. This may indicate that the use of lie detectors relying on skin conductivity gives psychopaths an advantage that non-psychopaths do not have in criminal investigations.
History[edit | edit source]
GSR originated in the early 1900s. It was used for a variety of types of research in the 1960s through the late 1970s, with a decline in use as more sophisticated techniques (such as EEG and MRI) replaced it in many areas of psychological research. GSR still sees limited use today, as it is possible to use with low-cost hardware (galvanometer).
Uses[edit | edit source]
GSR measurement is one component of polygraph devices and is used in scientific research of emotional arousal.
GSR measurement is also becoming commonplace in hypnotherapy and psychotherapy practice where it can be used as a method of detecting depth of hypnotic trance prior to suggestion therapy commencing. When traumatic material is experienced by the client (for example, during hypnoanalysis), immediate changes in galvanic skin response can indicate that the client is experiencing emotional arousal. It is also used in behavior therapy to measure physiological reactions such as fear.
See also[edit | edit source]
- Affective computing
- Electrical quackery
- Skin potential
- Skin resistance
references[edit | edit source]
- Pflanzer, Richard Galvanic Skin Response and the Polygraph. BIOPAC Systems, Inc.. URL accessed on 5 May 2013.
- 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
[edit | edit source]
- University of Kuopio page on GSR Use
- Quack "Electrodiagnostic" Devices by Stephen Barrett, M.D. (a Quackwatch paper)
- Cornell GSR Class Project
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