TV shows and movies drive some false ideas about lie detection. Shows like Lie to me or movies like Harry Potter use lying detection methods without strong scientific supports in their plots.
In Lie to me Dr Cal Lightman is able to detect lying by observing people's nonverbal behaviors. And he is almost always right. Yet as some researches suggest, even groups of people we expect to be the most accurate in detecting lies, like psychiatrists, do not have a better rate than the rest of us at this exercise. They do not detect lies at better than chance rates. So Dr Lightman should not be as confident as he is in his ability to find who lie and who do not. Some researches say that verbal cues stay better indicators of lying than nonverbal cues. For instance it is more useful to try to detect if a suspect gives few and inconsistent details, which would prove that he is lying, than to observe his behavior when he gives these details.
Another kind of lie detection largely used in TV shows and movies is the polygraph test. In movies suspects who lie about crimes they have committed cannot resist to the "lie detector" test. The lie detector test is even used in the TV show Exposed in order to see if your date is lying to you. The polygraph test is based on the Pinocchio response: it detects physiological changes (like an increase in heartbeating), which would prove that you are lying. Yet this test is not really accurate. Indeed it is more an arousal detector than a lie detector. So it is possible to pass the test even if you are lying. For instance people with psychopathic personalities can be labeled as "saying the truth" because their low levels of guilt and fear make them able to show low levels of arousal when they reply to incriminating questions.
The last myth about lie detection drives by movies is the "truth serum". Used in Harry Potter movies or in Wonder Woman comics (Wonder Woman's lasso forces criminals to say the truth), truth serums have been used in reality. Indeed, some US government organizations like the CIA used drugs called barbiturates to extract confessions from terrorists. But scientists discover that such drugs do not enhance memory, so they are not a good way to obtain true information.
As we saw, in contrary to what we can see in TV shows, it is not possible to distinguish with certainty true information to lies. So lying is still a domain in which we can improve our knowledge.
Sources:
Psychology: from Inquiry to Understanding, Second edition, Scott Lilienfield, 2011
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