GSR is a method of measuring the electrical conductance of the skin, which varies with its moisture level. This is of interest because the sweat glands are controlled by the sympathetic nervous system, so skin conductance is used as an indication of psychological or physiological arousal. There has been a long history of electrodermal activity research, most of it dealing with spontaneous fluctuations or reactions to stimuli.
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 or lie detector.
The devices which measure this response are often referred to as feedback instruments, in part because of how this response is generated or detected. If this response is measured “actively,” then a gentle electric current is passed through the body of the test subject to measure conductivity. A passive test measures the current that is generated by the person’s body itself. The feedback from this is what constitutes the measured galvanic skin response.
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