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lie detector
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Also called:
polygraph
Key People:
William Moulton Marston
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lie detector

Also known as: polygraph
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Britannica Editors
Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....
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History

lie detector, instrument for recording physiological phenomena such as blood pressure, pulse rate, and respiration of a human subject as he answers questions put to him by an operator; these data are then used as the basis for making a judgment as to whether or not the subject is lying. Used in police interrogation and investigation since 1924, the lie detector is still controversial among psychologists and not always judicially acceptable.

Physiological phenomena usually chosen for recording are those not greatly subject to voluntary control. A pneumograph tube is fastened around the subject’s chest, and a blood pressure–pulse cuff is strapped around the arm. Pens record impulses on moving graph paper driven by a small electric motor.

The Editors of Encyclopaedia BritannicaThis article was most recently revised and updated by Adam Augustyn.