Polygraph/lie detector test

I know for a fact that many individuals watch TV shows like Maury and Steve Wilkis which demonstrates a lot of lie detector testing for either cheating women and man or for molesters, but some people either dont believe in it or does not understand how it works. 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 Berkeley and a police officer of the Berkeley Police Department in Berkeley, California. Polygraph examiners, or polygraphers, typically begin polygraph test sessions with a pre-test interview to gain some preliminary information which will later be used for "control questions", or CQ. Criticisms have been given regarding the validity of the administration of the Comparative Questions test (CQT). The CQT may be vulnerable to being conducted in an interrogation-like fashion. This kind of interrogation style would elicit a nervous response from innocent and guilty suspects alike. Polygraphy has little evidence to support its use. Despite claims of 90% validity by polygraph advocates, the National Research Council has found no evidence of effectiveness. There have been no empirical theories established to explain how a polygraph measures deception. Recent research indicates that Functional Magnetic Resonance Imaging (FMRI) may benefit in explaining the psychological correlations of polygraph exams. It could also explain which parts of the brain are active when subjects use artificial memories. Most brain activity occurs in both sides of the ventrolateral prefrontal cortex, which is linked to response inhibition. This indicates that deception involves a subject’s inhibition of certain questions, such as attempting to be truthful while lying. Recalling artificial memories are known to activate the posterior cingulate cortex. However, fMRIs are limited to being expensive, immobile, and having inconsistent lying responses. Some researchers believe that reaction time (RT) based tests may replace polygraphs in concealed information detection. RT based tests differ from polygraphs in stimulus presentation duration, and can be conducted without physiological recording as subject response time is measured via computer. However, researchers have found limitations to these tests as subjects voluntarily control their reaction time, deception can still occur within the response deadline, and the test itself lacks physiological recording. So in conclusion you cannot 100% know if someone is lying because a polygraph test because not only is the test inaccurate but people can deceive the test.