Television shows, like Maury shown above, utilize the polygraph test on a regular basis to 'prove' that a partner is lying, cheating, or committing other dishonorable acts. In chapter 11 of the Lilienfeld text it says the largest organization of polygraph examiners claims that the polygraph test is 98 percent accurate. It is extraordinary claims like this that television shows tell their audience and participants, persuading them to believe that the polygraph results are correct. But are these results actually that accurate?
According to the Lilienfeld text, polygraph tests are based on the Pinocchio response, a perfect physiological or behavioral indicator of lying like spiked blood pressure, perspiration, and/or breathing. According to the USA Today article linked below, this means that lie detectors are more of an arousal detector, because scientists still do not know how the nervous system acts when it is lying. If a person responds higher to a control question like "Have you ever been tempted to steal anything from a candy store?" than to a relevant question like "Did you kill your brother?" then they pass the polygraph test. In a perfect world, guilty suspects would experience this heightened autonomic activity, while the innocent would not. However, this is usually not the case. Polygraph tests give a high rate of false positives, or deeming innocent people guilty because of their heightened physiological responses. False positives occur because innocent people are usually very worried about being wrongly convicted, which heightens their physiological responses to relevant questions. On the other hand, the polygraph tests can result in false negatives, or concluding that the guilty person is innocent. This occurs when the guilty person changes their responses to the control questions, allowing them to pass the test. Also, some guilty parties have psychopathic personalities, meaning they have low levels of guilt and fear, causing them to not respond highly to the relevant questions.
The USA Today article also says that the polygraph test is only 61 percent accurate, which is slightly higher than chance. Remember that the next time you watch Maury or MTV's Exposed, linked below. Also keep in mind that it makes for better television drama if the person is found to be a liar. How interesting would a television show be if the participants were all squeaky clean?