Polygraph (lie detector)
Instrument designed to record bodily changes resulting
from the telling of a lie. Cesare Lombroso, in 1895, was the first to
utilize such an instrument, but it was not until 1914 and 1915 that
Vittorio Benussi, Harold Burtt, and, above all, William Marston produced
devices establishing correlation of blood pressure and respiratory
changes with lying. In 1921 an instrument capable of continuously
recording blood pressure, respiration, and pulse rate was devised by
John Larson. This was followed by the polygraph (1926) of Leonarde
Keeler, a refinement of earlier devices, and by the psychogalvanometer
(1936) of Walter Summers, a machine that measures electrical changes on
the skin. A more recent innovation is a device, developed in 1970,
called the psychological stress evaluator, which measures voice
frequencies from tape recordings. Although the lie detector is used in
police work, the similarity of physical changes caused by emotional
factors such as feelings of guilt to those caused by lies has made its
evidence for the most part legally unacceptable. An assessment of such
devices by National Research Council (an arm of the National
Academy of Sciences ) found that they also were too unreliable to be
used in screening for national security purposes. The use of lie
detectors to screen employees and job applicants is highly
controversial. Bibliography: See E. B. Block Lie Detectors, Their History and Use (1977); C. Gugas The Silent Witness (1979); D. T. Lykken, A Tremor in the Blood (1981).
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