Galvanic skin response
Encyclopedia
Human skin
The human skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system. The skin has multiple layers of ectodermal tissue and guards the underlying muscles, bones, ligaments and internal organs. Human skin is similar to that of most other mammals,...
, which varies with its moisture level. This is of interest because the sweat glands are controlled by the sympathetic nervous system
Sympathetic nervous system
The sympathetic nervous system is one of the three parts of the autonomic nervous system, along with the enteric and parasympathetic systems. Its general action is to mobilize the body's nervous system fight-or-flight response...
, so skin conductance is used as an indication of psychological or physiological arousal
Arousal
Arousal is a physiological and psychological state of being awake or reactive to stimuli. It involves the activation of the reticular activating system in the brain stem, the autonomic nervous system and the endocrine system, leading to increased heart rate and blood pressure and a condition of...
. There has been a long history of electrodermal activity research, most of it dealing with spontaneous fluctuations or reactions to stimuli.
Description
The device measures the electrical conductance (which is the inverse of the electrical resistanceElectrical resistance
The electrical resistance of an electrical element is the opposition to the passage of an electric current through that element; the inverse quantity is electrical conductance, the ease at which an electric current passes. Electrical resistance shares some conceptual parallels with the mechanical...
) between 2 points, and is essentially a type of ohmmeter
Ohmmeter
An ohmmeter is an electrical instrument that measures electrical resistance, the opposition to an electric current. Micro-ohmmeters make low resistance measurements. Megohmmeters measure large values of resistance...
. The two paths for current are along the surface of the skin and through the body. Active measuring involves sending a small amount of current through the body.
Due to the response of the skin and muscle tissue to external and internal stimuli
Stimulus (physiology)
In physiology, a stimulus is a detectable change in the internal or external environment. The ability of an organism or organ to respond to external stimuli is called sensitivity....
, the conductance can vary by several microsiemens
Siemens (unit)
The siemens is the SI derived unit of electric conductance and electric admittance. Conductance and admittance are the reciprocals of resistance and impedance respectively, hence one siemens is equal to the reciprocal of one ohm, and is sometimes referred to as the mho. In English, the term...
. 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. The SCR 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
Polygraph
A polygraph measures and records several physiological indices such as blood pressure, pulse, respiration, and skin conductivity while the subject is asked and answers a series of questions...
or lie detector
Lie Detector
"Lie Detector" is a CD single by The Reverend Horton Heat. It was released in October 1998 on Sub Pop.-Personnel:*Jim "Reverend Horton" Heath - lead vocals, guitar*Jimbo Wallace - upright bass, vocals*Scott Churilla - drums, vocals...
.
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.
SCR is used widely in psychological research due to its cheap and effective nature . It works by measuring the sympathetic nervous systems reaction to stimuli. This means the neurotrasmitter involved, unlike most ANS responses is acetylcholine, not epinephine. The device usually measures the sweat in the palm of the hand, or sole of foot.
History
The scientific study of GSR began in the early 1900s. One of the first references to the use of GSR instruments in PsychoanalysisPsychoanalysis
Psychoanalysis is a psychological theory developed in the late 19th and early 20th centuries by Austrian neurologist Sigmund Freud. Psychoanalysis has expanded, been criticized and developed in different directions, mostly by some of Freud's former students, such as Alfred Adler and Carl Gustav...
is the book by C. G. Jung entitled Studies in Word Analysis, published in 1906. Wilhelm Reich
Wilhelm Reich
Wilhelm Reich was an Austrian-American psychiatrist and psychoanalyst, known as one of the most radical figures in the history of psychiatry...
also studied GSR in his experiments at the Psychological Institute at the University of Oslo in 1935-6 to confirm the existence of a bio-electrical charge behind his concept of vegetative, pleasurable 'streamings.'
GSR 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
Electroencephalography
Electroencephalography is the recording of electrical activity along the scalp. EEG measures voltage fluctuations resulting from ionic current flows within the neurons of the brain...
and MRI) replaced it in many areas of psychological research. As of 2010, skin conductance monitoring equipment is still in use because it is inexpensive (e.g. a galvanometer
Galvanometer
A galvanometer is a type of ammeter: an instrument for detecting and measuring electric current. It is an analog electromechanical transducer that produces a rotary deflection of some type of pointer in response to electric current flowing through its coil in a magnetic field. .Galvanometers were...
).
Uses
Skin conductance measurement is one component of polygraph devices and is used in scientific research of emotional or physiological arousalArousal
Arousal is a physiological and psychological state of being awake or reactive to stimuli. It involves the activation of the reticular activating system in the brain stem, the autonomic nervous system and the endocrine system, leading to increased heart rate and blood pressure and a condition of...
.
The E-meter
E-meter
An E-meter is an electronic device used during Dianetics and Scientology auditing. The device is a variation of a Wheatstone bridge, which measures electrical resistance and skin conductance. It is formally known as the Hubbard Electrometer, for the Church's founder, L. Ron Hubbard...
, which is used by the Church of Scientology
Church of Scientology
The Church of Scientology is an organization devoted to the practice and the promotion of the Scientology belief system. The Church of Scientology International is the Church of Scientology's parent organization, and is responsible for the overall ecclesiastical management, dissemination and...
, is a skin conductance measurement device.
Skin conductance measurement is also becoming more popular in hypnotherapy
Hypnotherapy
Hypnotherapy is a therapy that is undertaken with a subject in hypnosis.The word "hypnosis" is an abbreviation of James Braid's term "neuro-hypnotism", meaning "sleep of the nervous system"....
and psychotherapy
Psychotherapy
Psychotherapy is a general term referring to any form of therapeutic interaction or treatment contracted between a trained professional and a client or patient; family, couple or group...
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 sweat rate can indicate that the client is experiencing emotional arousal. It is also used in behavior therapy to measure physiological reactions such as fear.