The development of the polygraph test, to measure a suspect's honesty during interrogation, began in the 1890s. The modern polygraph test has been around since the 1930s. Wires connected to a suspect detect physiological changes and transfer that information to a graph, and a scientist then interprets the graph. The results are somewhat subjective.
Honesty tests rely on psychological measurements rather than physiological measurements. Honesty tests ask a series of questions, such as whether the test subject would return a lost wallet, to determine the likelihood that he would be dishonest. They are often used by employers before hiring or during investigations of employees suspected of corporate dishonesty.
Both polygraph tests and honesty tests are highly controversial. Both require some level of subjective interpretation by the polygraph scientist or honesty test psychologist. For the polygraph tests, it is possible for examiners to manipulate the results by carefully crafting the questions to elicit higher physiological responses. Results are rarely admissible in court.
A polygraph (popularly referred to as a lie detector) measures and records several physiological indices such as blood pressure, pulse, respiration, and skin conductivity while the subject is asked and 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.
The polygraph was invented in 1921 by John Augustus Larson, a medical student at the University of California at Berkeleyand a police officer of the Berkeley Police Department in Berkeley, California. According to Encyclopedia, the polygraph was on its 2003 list of greatest inventions, described by the company as inventions that "have had profound effects on human life for better or worse.
Many members of the scientific community consider polygraphy to be pseudoscience. Nonetheless, in some countries polygraphs are used as an interrogation tool with criminal suspects or candidates for sensitive public or private sector employment.
US federal government agencies such as the FBI and the CIA and many police departments such as the LAPD use polygraph examinations to interrogate suspects and screen new employees. Within the US federal government, a polygraph examination is also referred to as a psycho physiological detection of deception (PDD) examination.
Today, polygraph examiners use two types of instrumentation: analog and computerized. In the United States, most examiners now use computerized instrumentation.
A typical polygraph test starts with a pre-test interview to gain some preliminary information which will later be used for "control questions", or CQ. Then the tester will explain how the polygraph is supposed to work, emphasizing that it can detect lies and that it is important to answer truthfully. Then a "stim test" is often conducted: the subject is asked to deliberately lie and then the tester reports that he was able to detect this lie. Guilty subjects are likely to become more anxious when they are reminded of the test's validity. However, there are risks of innocent subjects being equally or more anxious than the guilty. Then the actual test starts.
Some of the questions asked are "irrelevant" or IR ("Is your name Chris?"), others are "probable-lie" control questions that most people will lie about ("Have you ever stolen money?") and the remainders are the "relevant questions", or RQ, that the tester is really interested in. The different types of questions alternate. The test is passed if the physiological responses during the probable-lie control questions (CQ) are larger than those during the relevant questions (RQ). If...