A procedure (or machine) designed to distinguish truth-tellers from liars.

Because emotional states are often accompanied by physiological arousal, researchers have often wondered if physiological measurements could be used to detect what a person is thinking or feeling. If you feel guilty for telling a lie, are there physiological cues that will betray you? The assumption that there are such cues forms the basic rationale behind the polygraph test. It is assumed that a guilty person will have increased autonomic arousal in response to certain key questions, compared to the arousal levels of an innocent person. In a conventional polygraph examination, GSR, blood pressure, and heart rate are monitored. GSR refers to galvanic skin response. Sweating causes a brief drop in the electrical resistance of the skin. This resistance (the GSR) can be measured by means of electrodes attached to the hand. An arm...