Popular Myths in Psychology

Myths about Emotion and Motivation

Myth: The Validity of the Polygraph Lie Detector Test

by Alicia Kassian

I was watching Maury the other day and a women was featured because she believed her husband was cheating on her. She was desperate to find out if he was lying to her so he was asked to take the polygraph lie detector test. In fact, he was lying and he had slept with over ten women since their relationship started. Now, that seemed true because his face said “uh oh” and he stormed off the stage, but most polygraph tests are not very valid. This particular guy was definitely guilty because he was caught cheating on his wife on camera at the filming of Maury (yikes). But, polygraphs in general are given heavy importance with a ton of flaws and many false positives (a non liar is given failing grade). Polygraphs only really work if the people being tested don’t know how they work. They measure changes in blood pressure and respiration and these supposedly go up if you are lying…unless you’re a “good liar” which means you do not get stressed or experience fear responses after or during a lie. So why do we still use them in the court of law? Because it can benefit either the defense or state depending on the results and then you can always dispute the reliability of the test. If you know of the movie Meet the Parents I’m sure you remember the father giving his future son-in-law a lie detector test to get into his “circle of trust.” Of course, he is rather a failure of a son-in-law in the movie and doesn’t do very well in his father in law’s opinion. The movie portrays the polygraph as a pretty accurate lie detector; which it isn’t! Also, a great number of people administering polygraphs are intimidating and use intimidation techniques to try and force a confession when that person may be innocent. This means that the person is likely stressed and fearful when the question is asked not because they are lying but because they are scared that they might go to jail or that people might not believe them, how sad is that? This happens to 40% of innocent people that are required to take a polygraph lie detector test. So, the next time you are watching Maury just know that polygraphs may not be so confirmatory, regardless of how guilty that alleged cheater may look.