The lie detector paradox

I’ve got an article in today’s Observer about the unreliability of ‘lie detectors’ but why people still tend to spill the beans when wired up to them.

It turns out that polygraphs have a sort of placebo effect, where people are more truthful because they believe that they work. In fact, studies show that people are more truthful when wired up to a completely bogus ‘lie detector’ look-alike.

Worryingly though, law enforcement is staring to use this effect, which is based entirely on ignorance, to monitor sex offenders and evaluate their risk of carrying out other sexual assaults.

Needless to say, I feel this is foolish. Read the article for the full details.

By the way, this is the first of an every-six-weeks column I’ll be writing for the paper. As my friends will tell you, I rarely manage to say anything interesting that frequently, so wish me luck.

Link to Observer article ‘the truth about lie detectors’.

6 thoughts on “The lie detector paradox”

  1. You want to read a great book on the lie detector? Go for Paul Ekman’s, “Telling Lies.” While the show, “Lie To Me,” is based upon it’s science; the show is not entirely accurate…

    No! TV stretched the truth!?


    There was one episode of, “Lie To Me,” where the main character (based on Ekman), Cal Lightman has an ostrich egg delivered to him. When certain, if I recall correctly, FBI agents came to him for advice on their new lie detector he had one of them hold the egg. And upon growing frustrated that Cal had shown the flaws in their device–the egg crushed easily within the hand of the person holding it. Laughingly, Cal says, “I’ve always wanted to try that. You see, that Egg is just as good as your machine because all it does is measures emotional response.” This is true for lie detectors..

    Back to the point; in the book, “Telling Lies,” Ekman created a chart, and extensive chart, that the humans asking the person the questions need ask in order to find the truth from the person. It takes skill to be a lie detector-ologist-person-who-uses-the-machine, and they need to know the right things to ask. And the right way to ask them.

    Now that I am far enough off the point of this article (concerning a placebo effect of lie detectors) I shall get back to reading it…

    Looks interesting…

    Deception detection and Paul Ekman is to me like Justin Bieber is to all the teenage boys who love her.

  2. Psychology has a long history of problems with lie detecting. Hugo Munsterberg got into major problems when he tried using psychological testing to test whether a defendant was lying in a 1907 murder case. It was a public relations fiasco that got him labelled “Professor Monster-work” by the media.

    The most famous “lie-detector” psychologist was William Moulton Marston (of Wonder Woman fame). The Frye standard for evaluating expert testimony in legal cases stemmed from his testimony in a 1920 murder case.

  3. A persons beliefs are not reality. A person doesn’t lie if they say that they were the victim of a car accident, but in fact they were the cause of the accident. They would pass a lie test, for in their reality they are innocent, but on video (impartial test) it would show them passing through a red right.
    From what I know of sex offenders “law enforcement is staring to use this effect”, many believe their victim enjoyed/wanted the crime, so feel no guilt and would therefor pass a lie detector.

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