Galvanic skin response

Galvanic skin response (or GSR), also known as electrodermal response (EDR) or psychogalvanic reflex (PGR), 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 responces.

One branch of GSR explanantion interprets GSR as an image of activity in certain parts of the body. The mapping of skin areas to internal organs is usually based on acupuncture point.

Practice
GSR is conducted by attaching two leads to the skin, and acquiring a base measure. Then, as the activity being studied is performed, recordings are made from the leads. There are two ways to perform a GSR - in active GSR, current is passed through the body, with the resistance measured. In passive GSR, current generated by the body itself is measured.

History
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
Because the GSR is relatively simple and well documented it can be used to detect subconscious semantic knowledge. For example suppose that two subjects are suffering from prosopagnosia, however one of these subjects gets a GSR while the other does not; from this we could infer that the two subjects suffered from different (although similar) neural disfunction.

Non-research uses
GSR has seen, outside of the research community, usage as a lie detector, under the theory that telling of lies increases perspiration, changing the conductance of skin. However, the variety and rapidity of some responses disproves this theory, as skin would have to 'un-sweat' or dry out in remarkable ways. Its accuracy, because of its limited scope, is believed to be even less significant than that of a regular polygraph.

GSR is also used by Scientologists, who call their devices E-meters, in their spiritual counseling. They claim to have developed a variety of techniques to improve the reliability and accuracy of the device.