I heard about this one on the radio this morning. It seems the Fox TV network (not the news network, just the regular broadcast TV one) has a new show out called “The Moment Of Truth.” The concept mixes reality TV with a gameshow and a bit of really bad science. Essentially, contestants are put on the stand and asked hard questions about what they have done and would do as well as other dark secretes. They win money by answering but they cannot lie because they’re hooked up to a “lie detector” and an operator will immediately call the fibs as soon as they are made.

Well, here’s the problem: The “lie detector” which is portrayed in the show does not really exist. What they actually are using is a machine which has been around for a long long time: The polygraph. The newer versions dispense with the old paper tape and instead use slick LCD readouts and have a computer tracking the variables instead of a paper plotter, but the theory is the same. The polygraph machine measures a number of variables of the subject including breathing rate, pulse, blood pressure, skin conductivity (which relates to sweating) and other similar factors.

So can it determine if you’re lying? No, not really. At best, it can tell if a question makes someone nervous, although even that is dubious. The basic theory behind the polygraph is that when someone is lying they will become tense and nervous or otherwise be less natural with their response. The problem with this is that it’s entirely subjective. It also depends heavily on the expectations of the subject.

In 2003, the National Academy of Sciences issued a stinging report on the quality of polygraph research and the use of the polygraph in both investigations and in screening for security clearance. The NAS report found the claims of reliability of the polygraph in detecting lies to lack scientific evidence. The report stated: “Its accuracy in distinguishing actual or potential security violators from innocent test takers is insufficient to justify reliance on its use in employee security screening in federal agencies.”

For this reason, operators generally call it a “lie detector” and not a “polygraph” and they make statements like “he was conclusively cleared by a polygraph.” Why? Because this communicates the idea that the device is indeed capable of detecting a lie. And this is key, because it is, at it’s foundation, a “psycological warfare.” In other words, the idea that a machine can detect a lie, whether or not true, is the most important aspect of the polygraph. If the person being interrogated believes that they will be caught lying they’re more likely to become nervous or even to crack and confess to something.

There really is no reliable way to tell if someone is lying with any kind of accuracy (this is why polygraphs are almost never admisable in a court of law), but there are certainly clues which might help a seasoned investigator. A suspect who is brought in and questioned about a certain event might stutter or become visibly nervous upon being asked certain questions. A good investigator could pick up on this and come to the conclusion that the person being interrogated is hiding something. Is this reliable, dependable and always accurate? Absolutely not. It’s entirely subjective and at best only helpful in limited contexts.

This is basically the same thing a polygraph operator does. Rather than simply listening to the voice of someone being questioned and watching their hand movements, they are also given a readout of their pulse and breathing level. While being able to read such variables may have some usefulness in judging the honesty of a subject, it is, in the end, only a judgment and no more reliable than any other hunch that a questioner might get. This is especially true in an atmosphere like a game show, where the pressure and excitement is nearly guaranteed to make a subject’s vital signs vary chaotically.

There have been attempts to develop a “true lie detector” by reading brainwaves or using an FMRI to peer inside the brain of a subject and determine if the answers are being drawn from memory or fabricated on the spot, but these too are not reliable, in part due to the complex psycological aspects of creating a lie. In many cases a person may be in a state of self-denial or have memorized their answer ahead of time.

Because of this, current technology offers no reliable or objective way of telling a lie from the truth in the foreseeable future. The only one lying here is the Fox network when they perpetuate the myth of the truth-or-lie detection machine. And that’s the honest truth!

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This entry was posted on Wednesday, January 23rd, 2008 at 1:46 pm and is filed under Bad Science, History, media. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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