DECEPTION TEST, a name given to the measurement of certain bodily changes caused by the effort of lying, or by fear due to a sense of guilt. Working at Graz, Austria, in 1914, Vittorio Benussi devised a test based on the idea that the rate of breathing is affected by the effort of telling a lie, and that this change could be accurately measured. Three years later Harold Burtt further developed this method in the Harvard Psychological Laboratory. In 1915 W. M. Marston, working in the same labora tory, had tested the relation of blood pressure to the effort of lying, but found that all persons examined showed blood pressure higher than normal whether they lied or told the truth.
A psychological deception test, based on association of words, was devised in Austria by Wertheimer and Klein in 1904, and developed by Carl Jung in Switzerland in 1905. Jung read a list of words to three nurses suspected of stealing a purse. Some of these words referred to objects which would have been seen when the theft was committed, and the suspects were asked to give associated words. In Jung's view the guilty nurse gave words which would not have been in the mind of an innocent person and further revealed guilt by delay in answering.
The vegetable alkaloid scopolamin was used by a Texas physi cian, R. E. House, with the idea that it produced a garrulous semi-intoxication in which the truth was likely to be blurted out. Another test depends on the variation in electrical conductivity of the skin caused by the secretion of sweat under pressure of emo tion. The objection to these forms of trial by ordeal is that they are considered too uncertain to be used with assurance in crimi nal trials.