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Polygraph
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<p>A polygraph, often incorrectly referred to as a lie detector test, is a <a href="/facts/Pseudoscientific/kdNzoLeS">pseudoscientific</a> device or procedure that measures and records several physiological indicators such as <a href="/facts/Blood_pressure/VtqqSM2J">blood pressure</a>, <a href="/facts/Pulse/Bg8EUcWL">pulse</a>, <a href="/facts/Respiration_(physiology)/KKWAJIbd">respiration</a>, and <a href="/facts/Electrodermal_activity/aN4gyXhb">skin conductivity</a> while a person 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; however, there are no specific physiological reactions associated with <a href="/facts/Lying/mfQgWIjd">lying</a>, making it difficult to identify factors that separate those who are lying from those who are telling the truth. </p><p>In some countries, polygraphs are used as an <a href="/facts/Interrogation/UPPgqVFQ">interrogation</a> tool with criminal suspects or candidates for sensitive public or private sector employment. Some <a href="/facts/United_States_law_enforcement/VH7e0Cdt">United States law enforcement</a> and federal government agencies, as well as many police departments, use polygraph examinations to interrogate suspects and screen new employees. Within the <a href="/facts/US_federal_government/VJCxUaf7">US federal government</a>, a polygraph examination is also referred to as a psychophysiological detection of deception examination. </p><p>Assessments of polygraphy by scientific and government bodies generally suggest that polygraphs are highly inaccurate, may easily be defeated by countermeasures, and are an imperfect or invalid means of assessing truthfulness. A comprehensive 2003 review by the <a href="/facts/National_Academy_of_Sciences/M3oePVeG">National Academy of Sciences</a> of existing research concluded that there was "little basis for the expectation that a polygraph test could have extremely high accuracy." The <a href="/facts/American_Psychological_Association/907fEfuc">American Psychological Association</a> states that "most psychologists agree that there is little evidence that polygraph tests can accurately detect lies." </p>