How does a Lie detector work?
How does a Lie detector work? A lie detector, also known as a Polygraph test works by detecting physiological changes due to a psychological stimulus. The earliest version of the instrument was developed in 1921 by John Larson who combined changes in respiration, heart rate and blood pressure as physiological changes that occur when a person is lying. The modern polygraph is a technologically advanced system that measures the same parameters with high levels of accuracy with computers. The theory behind lie detection tests are that when people are lying they experience a different emotional state when compared to telling the truth, it is believed that in high stake scenarios, being anxious or afraid of getting caught when being guilty of an offense manifests physiologically. This is due to the sympathetic nervous systems response of flight and fight that releases hormones which increase heart rate, elevate body temperature and respiration. The term polygraph originates from the