A
polygraph, popularly referred to as a
lie detector, 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. The belief underpinning the use of the polygraph is that deceptive answers will produce physiological responses that can be differentiated from those associated with non-deceptive answers; the polygraph is one of several devices used for
lie detection.