Mythbusters Perpetuates the Myth of the Lie Detector

Cross-posted from the AntiPolygraph.org forum:


The secondary topic of the latest episode of Discovery Channel's popular Mythbusters program (Season 5, Episode 24 "Confederate Steam Gun"), which aired on Wednesday, 5 December 2007, is the supposed "myth" that it is possible to beat a polygraph test. (It is, despite the show's conclusion that it is merely "plausible." For documentation, see The Lie Behind the Lie Detector [1 mb PDF].) The episode will re-air this Saturday, 8 December. I encourage all to watch.

In the episode, Mythbusters inexplicably fails to explain the truth about how a polygraph "test" actually works and (knowingly as I shall explain) presents a phony Ph.D. as an authority on matters of polygraph validity.

Here's how polygraph "testing" actually works: The examinee is not supposed to know that secretly, the examiner expects answers to the so-called "probable-lie control questions" to be less than truthful. An example of a commonly-used control question is, "Did you ever lie to get out of trouble?" The examinee is steered into a denial through the suggestion, for example, that anyone who would lie to get out of trouble is the same kind of person who would commit the crime under investigation and then lie about it. But secretly, it is expected that everyone has lied to get out of trouble -- even those innocent of the crime.

Reactions to the control questions are then compared to reactions to the relevant questions (those directly concerning the incident under investigation), for example, "Did you take that money from that office?" If reactions to the control questions are greater, the examinee passes. If reactions to the relevant questions are greater, the examinee fails.

This simplistic methodology has no grounding in the scientific method and is inherently biased against the truthful, because the more honestly and fully one answers the control questions, and as a result feels less anxiety when answering them, the more likely one is to wrongly fail.

The procedure also includes irrelevant questions such as, "Are the lights on in this room?" The polygrapher falsely expains that such questions provide a "baseline for truth" because the true answer is obvious to both examiner and examinee. But in fact, these irrelevant questions are not scored at all, but merely serve as buffers between pairs of relevant and control questions.

Mythbusters explained none of this critically important information to the audience, although they could have easily done so in a minute or two.

Again, the key to passing or beating a polygraph test is to exhibit stronger reactions to the control questions than to the relevant questions. Methods for doing this include the techniques of tongue-biting and mental activity (such as thinking exciting thoughts) that were shown on the episode. But these must be done timely with the asking of the control questions.

Instead, the Mythbusters personnel were told to apply countermeasures "when telling the truth." It appears that they wrongly applied their countermeasures when answering the unscored irrelevant questions. It is hardly surprising that such misapplied countermeasures did not result in passing scores.

The polygraph operator who appeared on the show is none other than the infamous "Dr." Michael Martin, whom AntiPolygraph.org has previously unmasked as a phony Ph.D. who obtained his "doctoral degree" from an unaccredited diploma mill. He is seen in a video clip currently available on the Discovery Channel website suggesting a 98% accuracy for polygraphy -- a scientifically unfounded claim that goes unquestioned by the Mythbusters staff:

http://dsc.discovery.com

The Discovery Channel's message board has a thread about this episode titled, Confederate Steam Gun - Beat The Lie Detector! - Discuss It Here!. (I have made several posts to this thread. I registered and posted under the name "George Maschke," but somehow, perhaps a database corruption, the user names associated with my posts have changed.)

I can reveal that in August of this year, I was contacted by two of Mythbusters' producers. They had seen my appearance on a 2003 British television program, and after a lengthy and pleasant telephone conversation, they were interested in having me either come to San Francisco to appear on the show or be interviewed via webcam.

One of the topics I was asked about in the course of our phone conversation was a polygraph examiner who might be suitable to appear on the show. They were initially interested in Bruce Burgess, who appeared in the same British show as I previously had. In a follow-up e-mail sent on 31 August 2007, I specifically warned them, in the event they chose to seek a polygraph examiner closer to home, against three prominent polygraph operators whom AntiPolygraph.org has identified as phony Ph.D.s: Ed Gelb, James Allan Matte, and Michael Martin. And I included the same hyperlinks you see here. The producers did not reply to my e-mail and did not contact me again.

Mythbusters cannot say they were not warned about Michael Martin's credentials. I think they owe the public an explanation of why they knowingly chose a fraud to appear on the show and allowed him to be presented as "Dr." Martin.

Oh dear. That's both surprising and disappointing. I hope they have the sense to show a retraction, although actively discrediting the good "Dr" may be a bridge too far in political/legal terms.

Don't know about that topic, but related is their Is Yawning Contagious? episode that was less than careful:

http://www.statisticool.com/mythbusters.htm

I seem to recall reading that an ex-CIA operative maintained that you could beat a lie detector test by placing a thumb-tack in your shoe and sticking yourself at the appropriate time.

I've also had a tough time believing you can't beat one by asking yourself and alternative question in your mind and answering that one instead. Granted, I've never taken or administered a polygraph, but I clearly understand why it's considered to be more of an art then a science.

T'ai Chi said:

Don't know about that topic, but related is their Is Yawning Contagious? episode that was less than careful:

http://www.statisticool.com/mythbusters.htm

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Yup. Fisher's one tailed p = .0512782 when I checked it.
As those old carneys used to say, "Close, but no cigar."
Now a parapsychologist would probably say that she needed a larger n, because as we all know, the ns justify the means.

T-Diddy said:

I seem to recall reading that an ex-CIA operative maintained that you could beat a lie detector test by placing a thumb-tack in your shoe and sticking yourself at the appropriate time.

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Tory had a thumbtack, but they had motion sensor (some sort of pressure pad under his feet) and whenever he moved to jab himself the examiner noticed it.

Steve S.

Wouldn't a valid test have to include something worth lying about-- something with dire consequences like getting fired or not hired.

What did the Mythbuster lie about (I'm lying when the ask whether I like chocolate versus whether I stole the money would seem like 2 completely different scenarios).

Lying is bad.

As is withholding information when you know it should be given.

bpesta22 said:

Wouldn't a valid test have to include something worth lying about-- something with dire consequences like getting fired or not hired.

What did the Mythbuster lie about (I'm lying when the ask whether I like chocolate versus whether I stole the money would seem like 2 completely different scenarios).

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They used a staged theft of money from an office, but they did have actual consequences. In the polygraph machine test, if they failed they had to wash the cars fo the entire crew and cast...if they beat the machine they got to fly first-class on their next trip for the show.

They did a similar thing when they tested the functional MRI. They had to steal either a watch or ring from a drawer, and the test would determine which they took. The losers had to ride the bus back from Florida (Grant beat that one).

I had to take a polygraph test during a job interview process. I found it degrading and humiliating. I failed the test in spite of the fact that I was 100% truthful. It's just absurdly unfair.

Swagomatic said:

I had to take a polygraph test during a job interview process. I found it degrading and humiliating. I failed the test in spite of the fact that I was 100% truthful. It's just absurdly unfair.

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I think Bob Park said it best:

Bob Park said:

The polygraph, in fact, has ruined careers, but never uncovered a single spy.

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I believe that was how the Soviets managed to get their spies into the CIA, all they had to do at the time was beat a polygraph because at the time it was thought that the polygraph doesn't lie.

If everyone here is that cheesed off about this Mythbusters episode, then email them - they do revisits/corrections when enough people complain about their handling of any particular myth. While the show is primarily for entertainment, and they openly admit that their tests are less than 100% scientific, they do seem to honestly try their best on these things.

I would just like to add that while watching that episode, I got the impression that the polygraph dude was a scumbag. You know what I mean... sometimes you can just tell by the way a person looks and acts...

That is neither here nor there but hey..

I didn't see the show, but it sounds like they may have perpeuated the myth of the lie detector in another way (possibly they discussed this?).

Lie detectors are to be used as an interviewing tool, to allow the operator to focus on certain events and get the person who is being interviewed to feel that he can't lie about what happened during an extended interview. The lie detector result itself isn't as useful as the information from the interview generated by the lie detector test. It's (supposed to be) another tool, not an end in itself. It's been highly misused by some who take the actual lie detector reading as a complete answer to a question.

I like Mythbusters, BTW, one of the few TV shows I'll actually sit down & watch most of (along with that Everest show...)

Swagomatic said:

I had to take a polygraph test during a job interview process. I found it degrading and humiliating. I failed the test in spite of the fact that I was 100% truthful. It's just absurdly unfair.

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Gosh, I hate woo.

Wildy said:

I think Bob Park said it best:
The polygraph, in fact, has ruined careers, but never uncovered a single spy.

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Bob Park hasn't responded to my questions about that statement. See http://www.internationalskeptics.com/forums/showthread.php?t=86050

If all they wanted to test is whether the polygraph machine and the polygraphist could be fooled without having to worry about whether polygraph machines can actually detect lies or not, perhaps they should have gone for a "Guilty Knowledge" like test, instead of trying to get people to lie.

They might for example do the following test: have a test subject throw a die, remember the number thrown and writing it down on a piece of paper which is placed in a sealed envelope, so it can be checked later. The test subject will then be prepared to undergo to polygraph test. The polygrapher calls out all numbers from one to six in random order. The test subject would react differently if the number he threw is called. Even inexperienced people using nothing more than a simple skinresistance meter are usually able to find out what the number is, that is to say: if the test subject does not attempt to fool the machine.

If on the other hand the polygraph can be fooled, then it should be possible to effectively hide the correct number from the polygrapher, or even get him to think a different number was thrown. Repeat the test ten or so times and you should get a good indication how effective a method of fooling the polygraph(er) is. If the polygrapher can be fooled in a guilty knowledge test, he can be fooled using any other methodology.