All tissues in the human body, including skin, have the ability to conduct electricity. Indeed, this is how nerves function to relay information from one part of the body to another. The skin also has electrical activity, which is in constant, slight variation, and can be measured and charted. The skin's electrical conductivity fluctuates based on certain bodily conditions, and this fluctuation is called the galvanic skin response.
Sudden changes in emotion, such as fright, can trigger this response, as can other types of changes, such as the hot flashes that are characteristic of menopause. The galvanic skin response can be graphed on a chart for observation, in the same way that heart or brain activity is recorded. Even though this is the case, it is impossible to detect the type of emotion or physical change that elicited the reaction by simply looking at the graph.
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.
The most well-known use for measuring the electrical conductivity is as a part of a polygraph or "lie detector" test. The reaction of the body is measurable by this and many other parameters, when a person tells a lie. Knowingly stating a falsehood is, in a physiological sense, stressful and unnatural. A change in the conductivity of the skin, as well as changes in breathing, heartbeat, and perspiration, is one of the body's responses to the stress of lying.
Measuring the response can also be an important element of certain psychotherapy treatments, as well as behavioral therapy. Research studies involving stress and anxiety levels have also been carried out with attention to this response. Other, purely scientific applications have been found for it as well. One good example of this is the touchscreen monitor.
These display screens operate by detecting the skin's electrical conductivity. Users of touchscreen monitors may have noticed that these devices work poorly when they are wearing gloves. In fact, they may not work at all in this case, because the gloves not only insulate against heat transfer, but also the detection of electrical currents present in the skin.