Definition:
For most people, there does not seem to be any reason to think that the use of
lie detectors is not scientific. Strictly speaking, they are not designed to
detect lies as such - instead, they detect physiological changes. These machines
are used to measure "stress" through variations in physiological variables like a
person's blood pressure. These variations are presumed to be causes by stress,
and stress is often brought about by lying. Thus, it is assumed that the presence
of stress when answering a question indicates that the answer was not truthful.
This, however, confuses correlation with causation - and whereas the first assumption above is not really questioned, the second two are very questionable. The mere fact that a person experiences stress when answering a question does not mean that they are lying - the stress could be caused by other things. After all, the usual circumstances when administering a lie detector test involve extreme stress, for example when a person is accused of muder.
Supporters of the use of lie detectors will readily admit this and argue that such problems are factored out of the test. Whoever is administering the test will first ask control questions in order to establish a "base line" reading. Questions on simple topics, like a person's name and occupation, are asked and the subject is asked to sometimes tell the truth and sometimes lie. This, in turn, is supposed to show just how much more stress a person exhibits when lying as opposed to when they are telling the truth.
However, the mere act of doing this removes the use of lie detectors from pure science. The administration of this test now contains a strong component of human interpretation instead of simply reading off numbers from an objective measuring device. Interpretations are open to question and disagreement. In addition, these control questions can be used to cheat. A person answering truthfully can do something deliberate to increase their stress, like biting their tongue very hard. Methods exist to beat lie detectors, and they can be effective. Because of this, reliance upon them is more a matter of pseudoscience rather than science.
Use of polygraphs is not irrelevant - many people have had their careers destroyed because of the erroneous results from so-called "lie detectors." David King, 20-year Navy veteran, sat in prison for almost 18 months and endured multiple polygraph sessions, some up to 19-hours long. A military judge dismissed all charages against him.
Mar Mullah was a career agent with the FBI who was targeted for a massive investigation, including a surprise nighttime search of his home and a close review of every financial record, every calendar entry, and eve his "to-do" lists. Why? Because of a "positive" result during a single polygraph session.
No evidence of any wrongdoing was ever discovered and his bade was eventually returned - but not before his career was destroyed. He was never above suspicion again and the culprit was a polgraph oeprator with a mere 10 weeks of training. In most states, even barbers are required to be in training for 26 weeks before they can get a license to cut people's hair.
The unreliability of lie detectors has also, finally, been recognized by at least some government agencies. After nineteen months of research, the National Research Council (an arm of the National Academy of Sciences), found that "national security is too important to be left to such a blunt instrument" and pointed out that no spy had ever been caught through the use of lie detectors.
Also Known As: polygraph test
Alternate Spellings: none
Common Misspellings: none
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