thewinterotter:

A heads up because I think most people don’t realize this: polygraph or “lie detector” tests are absolutely 100% junk science, about as accurate in determining a person’s truthfulness as a flip of a coin would be.

This paragraph from the main article linked above is a perfect sum-up:

The two biggest problems, writes the APA, are these: there’s no way to know if the symptoms of “bodily arousal” (like an elevated pulse) that the machine measures are caused by lies, and there’s no way to know if someone’s results are affected by the fact that they believe in the polygraph machine. If this second view is correct, they write, “the lie detector might be better called a fear detector.”

What I find really bizarre is that although these tests are known to be unreliable enough that they aren’t even admissible in US courts, police seem to actually genuinely believe in them. (Sort of like how they believe they can determine guilt through a suspect’s body posture, gestures, or “micro expressions” during interrogation.) They also very clearly take refusal to subject yourself to a polygraph as proof of guilt, just like they’ll take the results of the polygraph as proof of guilt, even though both are terrible metrics for determining those things. Government agencies, like the FBI and CIA, are even still allowed to use polygraphs to screen potential employees, even though the results of these tests are known to be unreliable.

This info is useful if you’re ever suspected of a crime – NEVER consent to a polygraph, even if you’re 100% innocent, even though it will make police think you’re hiding something – but also just as general information. Like if you’re a writer of crime thrillers, you can absolutely depict a cop as taking a polygraph failure as proof of a suspect’s guilt, because that’s pretty accurate, but you probably don’t want to make the narrative itself support that as some sort of scientific or irrefutable truth, because it definitely isn’t, and perpetuating the idea of the polygraph’s mythic and impossible ability to somehow detect deception is literally harmful to society.