Polygraph

Polygraph (also known as a lie detector test or deception detection test) is a device or procedure that measures and records several physiological indicators such as blood pressure, pulse, respiration, and skin conductivity while a person answers a series of questions. The belief underpinning the use of the polygraph is that deceptive answers will produce physiological responses that can be differentiated from those associated with non-deceptive answers.

History

The polygraph was invented in 1921 by John Augustus Larson, a medical student at the University of California, Berkeley and a police officer of the Berkeley Police Department in Berkeley, California. The polygraph was on the Encyclopædia Britannica 2003 list of greatest inventions, described as inventions that "have had profound effects on human life for better or worse."

Method

The polygraph measures physiological changes caused by the sympathetic nervous system during questioning. Some of the most common methods used include the Control Question Technique (CQT) and the Guilty Knowledge Test (GKT).

Criticism and controversy

The accuracy of the polygraph has been contested almost since the introduction of the device. In 2003, the National Academy of Sciences (NAS) stated that the majority of polygraph research was "unreliable, unscientific and biased".

Legal status

In the United States, the use of polygraph is widely used in law enforcement and for security clearances. However, its use in court is generally not allowed, following the 1998 Supreme Court case, United States v. Scheffer.

See also

• Forensic psychology
• Voice stress analysis
• Functional magnetic resonance imaging

External links

• American Psychological Association's article on Polygraphs

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Polygraph

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