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The Polygraph Theory

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A polygraph commonly known as a lie detector is designed to detect deception and false statements. Polygraph measures and records bodily functions such as blood pressure, pulse, respiration, and skin conductivity during questioning of a subject. The theory behind the polygraph machine and examination is that deceptive answers from the subject will produce physiological responses that are different than truthful answers. The polygraph has been surrounded by controversy for years due to its limitations and inaccuracy, and is not considered reliable as evidence in most court cases.
The Polygraph Theory
In order to understand the limitations of the polygraph, one needs to understand the theory behind the polygraph. The theory behind the polygraph is broken down into three steps with the first being the psychological theory of a lie or false answer. The psychological theory of a lie claims that emotional changes occur in a person while being questioned which in turn causes physiological changes that can be detected by the examiner during the examination process. The second part of the theory is called
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The theory behind countermeasures is that the test can be defeated by the subject performing physical acts or by using drugs to deal with the stress of specific questions. For example a person could momentarily hold their breath, perform mental math, squeeze he sphincter muscle, or bite their tongue just to name a few of the physical countermeasures. As stated the use of drugs can also relax a person and fool the machine in theory (Fienberg, 2003). There is evidence out there that show that countermeasures are being used to beat the polygraph examination and the evidence shows that countermeasures are effective. There are even websites and articles that will teach a person how to use countermeasures to defeat the lie
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