Evidence that the polygraph is completely bogus continues to pile up

Why are these machines still in use at all?

This is a very good piece that includes the well-deserved skepticism for the use of this device.

Glitch in widely used polygraph can skew results | Wichita Eagle.

Police departments and federal agencies across the country are using a type of polygraph despite evidence of a technical problem that could label truthful people as liars or the guilty as innocent, McClatchy has found.

The technical glitch produced errors in the computerized measurements of sweat in one of the most popular polygraphs, the LX4000. Although polygraphers first noticed the problem a decade ago, many government agencies hadn’t known about the risk of inaccurate measurements until McClatchy recently raised questions about it.

The manufacturer, Lafayette Instrument Co. Inc., described the phenomenon as “occasional” and “minor,” but it couldn’t say exactly how often it occurs. Even after one federal agency became concerned and stopped using the measurement and a veteran polygrapher at another witnessed it repeatedly change test results, the extent and the source of the problem weren’t independently studied nor openly debated. In the meantime, tens of thousands of Americans were polygraphed on the LX4000.

The controversy casts new doubt on the reliability and usefulness of polygraphs, which are popularly known as lie detectors and whose tests are banned for use as evidence by most U.S. courts. Scientists have long questioned whether polygraphers can accurately identify liars by interpreting measurements of blood pressure, sweat activity and respiration. But polygraphers themselves say they rely on the measurements to be accurate for their daily, high-stakes decisions about people’s lives.

It’s amazing this is being used, still. As one quote from a professor who researched polygraph testing says, “We’re talking about using a procedure that has a very weak scientific foundation and making it worse,” said William Iacono. “I already don’t have very much confidence in how government agencies conduct these tests. Now, they might as well be flipping a coin.”

When the polygraph is considered in its entirety, it should be thrown in the trash can but the hold on some can’t be loosened. And perhaps they are used mostly as an intimidation device. How fair is that?


  13 comments for “Evidence that the polygraph is completely bogus continues to pile up

  1. May 28, 2013 at 12:08 AM

    Polygraphy thrives on public ignorance. The myth of the lie detector was built up in the United States by uncritical yellow journalism in the early 20th century. Now in addition, it’s fed through daytime TV talk shows like Dr. Phil, Maury, and Steve Wilkos.

    But another factor contributing to polygraphy’s staying power is that it has become the official pseudoscience of the United States government, which operates the world’s foremost polygraph school at Fort Jackson, South Carolina. More than a dozen federal agencies have polygraph branches, and they rely on polygraph chart readings as if they had some probative value. Decisions to hire or not hire are made based on polygraph outcomes, and they’re allowed to direct (or misdirect) criminal and intelligence investigations as well.

    So it’s great to see an article on polygraphy on a skeptic website like this one. We may all chuckle from time to time at people who believe in far-out things like alien abductions, but it’s important to realize that serious people are fooled by pseudoscience such as this, and it has dangerous consequences for public policy as well as the individuals who are subjected to this latter-day trial by ordeal.

    Thanks for helping to spread the word!

  2. May 28, 2013 at 12:53 AM

    Polygraph tests were used in pretty much all the major UFO abduction cases. I imagine this is because of the absence of any corroborating physical evidence. Proponents needed some science-y corroboration, and since the abductees tended to believe their stories, polygraphs were an easy choice.

    Pseudoscience used to verify pseudoscience — perfect!

  3. May 28, 2013 at 6:38 AM

    For a bit of humor on this subject: http://www.snopes.com/legal/colander.asp

  4. May 28, 2013 at 6:46 AM

    Polk county Sheriff Grady Judd requires all applicants for employment to pass a polygraph

  5. May 28, 2013 at 8:34 AM

    I worked in a state prison for five years. Every inmate knew how to beat a polygraph test. Simply contract your sphincter for every question asked.

  6. JC
    May 28, 2013 at 8:37 AM

    I recall a Psychology Professor telling our class that a thumb tack in the shoe, or biting down on your tongue will skew results. Used during the baseline questions to spike blood pressure and heart rate, it will throw off the rest of the interview. This professor demonstrated the technique and then we had a go.
    agent j

  7. Chris Howard
    May 28, 2013 at 10:26 AM

    I always thought that even if they did work they could only be said to measure the subjects conviction, or belief that what they’re saying is true, not the actual truth.

  8. Nathan M.
    May 28, 2013 at 10:40 AM

    This may sound defeatist, but to save face, in order to get these agencies to stop employing the devices, we’d have to provide them with a magical device that actually delivers on the polygraph’s promise. None exists.

    What they won’t do is to stop using them even if they’re demonstrably worse than useless. It would reopen too many compromised investigations. I hope I’m mistaken, and it would follow a path more like DNA testing.

  9. J
    May 28, 2013 at 12:19 PM

    From what I’ve read in books on police interrogation, polygraph tests aren’t seen as being effective because of how they work, but rather because of what the person being interviewed believes about them. If you go in under duress and are trying to lie your way through an interview, a polygraph would appear to be an intense pressure to maintain consistency, and so coming clean could be a more desirable outcome, in only to lift the burden of accusation and all the paranoia that can entail.
    As in the picture from The Simpsons, “Alright, a Sears catalogue…”
    But then you have the rapport you build with the interviewer anyway, which is what tends to matter a lot more (because they’re observing you, not just recording bodily functions), and even then people make mistakes, though it’s better than trying to figure out if someone’s nervous because they’ve always been afraid of a subject or if the subject itself has recently become fearful based on “readings”. Not to mention the fact that polygraphers are needed to interpret what the machine shows so they can ask control questions alongside the relevant ones and form a baseline for what the interviewee acts like when telling the truth, which is essentially just another way to establish rapport.
    So I tend to take a consequentialist view and say it’s useful with those who believe in it, much like a bible is useful for a believer on trial.

  10. drwfishesman
    May 28, 2013 at 12:45 PM

    I had to take a polygraph when I was in the Marine Corps because I had access to secure communication codes. They did it at random and it didn’t matter your rank. I had to drive down to the NCIS office in San Diego to get it done by the lovliest young lady I had ever seen. When she put the spring coils around my chest, the machine went crazy. She looked at me and asked if I was a little nervous. I just smiled like an idiot 19 year old male. The questions were interesting but extremely simplistic and I answered them honestly. Did I have contacts with a foreign government? (no), Had I ever lied to impress someone? (yes), Had anyone ever approached me about the work I do with classified material? (no). The special agent asked me what I thought after the test was over and I asked how she could tell the difference between truthful nervous and lying nervous…she said she couldn’t, but some agents claimed they could. I look back and find that very chilling when I think about it.

  11. May 28, 2013 at 11:16 PM

    I wrote THE book about it: THE CLAPPER MEMO (May 2013). Available at Amazon.com.

  12. May 29, 2013 at 8:59 PM

    J, I might be initially inclined to agree, thinking, “I don’t have anything to hide, and even if I did I could beat it, so what’s the big deal?”

    But the problem also this: once you sit down with that polygraph specialist, you’re at his/her mercy. Even if it’s only effective as a psychological leverage during an interrogation, it’s still also going to be useful as a Witch Test if the specialist or their supervisor wants to ruin or has a bad feeling about you.

  13. Albert J K III
    May 31, 2013 at 12:41 PM

    Look around for Penn and Teller’s show B**L S**T on youtube about polygraphs. Or, watch an episode of Maury Povich. One time I took one for a job I was told that I was relaxing too hard. ?????????

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