- lie detector
a polygraph used to determine changes in certain body activities, as blood pressure, pulse, breathing, and perspiration, the results of which may be interpreted to indicate the truth or falsity of a person's answers under questioning.[1905-10, Amer.]
* * *or polygraphInstrument for recording physiological phenomena (including blood pressure, pulse rate, and respiration) of a human subject as he or she answers questions asked by an operator.These data (recorded as graphs) are used as the basis for judging whether the subject is lying. The phenomena usually chosen for recording are those not easily controlled voluntarily. The types of questions asked, their wording, and the mode of presentation have a tremendous effect on the results and their reliability. Used in police interrogation and investigation since 1924, the lie detector is still controversial among psychologists and not always accepted as evidence in courts.
* * *also called Polygraph,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.
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