Wednesday, May 03, 2006

Lie Detectors (still) Don't Work!


Submitted by TroyM; comments by blogger jgl

Everybody knows that polygraphs don't work. With the possible exception of talk show hosts, the public, police, lawyers, and polygraph examiners.

In addition to the original article, John Daly has blogged some good material on the perception of infallibility of the forensic field.

The CIA, the FBI and other federal agencies are using polygraph machines more than ever to screen applicants and hunt for lawbreakers, even as scientists have become more certain that the equipment is ineffective in accurately detecting when people are lying.

Instead, many experts say, the real utility of the polygraph machine, or "lie detector," is that many of the tens of thousands of people who are subjected to it each year believe that it works -- and thus will frequently admit to things they might not otherwise acknowledge during an interview or interrogation.

Many researchers and defense attorneys say the technology is prone to a high number of false results that have stalled or derailed hundreds of careers and have prevented many qualified applicants from joining the fight against terrorism. At the FBI, for example, about 25 percent of applicants fail a polygraph exam each year, according to the bureau's security director.

In the popular mind, fueled by Hollywood representations, polygraphs are lie-detection machines that can peer inside people's heads to determine whether they are telling the truth.

The scientific reality is far different: The machines measure various physiological changes, including in blood pressure and heart rate, to determine when subjects are getting anxious, based on the idea that deception involves an element of anxiety. But because an emotion such as anxiety can be triggered by many factors other than lying, experts worry that the tests can overlook smooth-talking liars while pointing a finger at innocent people who just happen to be rattled.

25%! 25%! Somebody warn Maury Povich! I have a chip on my shoulder over this as I've had my career negatively altered because of this crap. I particularly like how they say the real utility is that people "believe" it works. Using this thing on applicants for forensic scientist positions is like placing a 40-year-old cynic on Santa's lap. (or something like that).

8 comments:

Anonymous said...

It's a little scary when I take time a think about how often polygraphs are probably being used. Every person can handle their anxiety differently and the polygraph can work against the truly innocent. It seems as if the polygraph test is more of a hinderance than help. Just scary, very scary.
-jjs

Anonymous said...

I believe that there some be more research about Lie Detectors. I don't think considering the anxiety of a person is good in determining the result of the Lie Detectors. It's a very mind-wrecking thing to think about because there may be people who are actually telling the truth, but may have some kind of health problem, that can trigger their anxiety, and make the test reads falsely. I think about the Maury show, and how the test sometimes shows that a person is cheating on their mates. What if that person is actually innoncent? A home, or a person life shouldn't be destroyed by a Lie Dector tests, that in my opinion is not 100% accurate. To sum it all up, I think more research should be done on "Lie Dectectors."
-CS-

Anonymous said...

There "should" be more research.
-CS-

Forensic Bloggers said...

yeah, these lie detectors are garbage. a dinosaur technique that is only around becuase it scares people into being honest.

CS and jjs bring up a good point about the tests having no way to determine if a person is nervous or lying. There is no way to determine an error rate.

and i always cringe when thinking about maury. or connie chung. or both of them. bleh.

debunkscience said...

I believe it's the actual interview that makes the test .The interviewer either gets a good feel for you or not . Testing heart rate , breathing , sweat gland , I mean lets be real people . It only proves that you are uncomfortable with a question or line of questioning.If the machine worked with no error it would be in every court and police station in the world. No need for trials , no need for much at all. Since we all know it's not , kinda shows it has no real validity in the system. I may hate discussing a topic , therefore when it's presented in a manner of interrogation , I most likely will be full of lots of anxiety....does this mean I'm not telling the truth ?? Just means I don't want to talk about it .With a world so advanced kinda strange we use such a device.The whole " I am going to colaborate the machine to you so pick a card trick" ...come on folks.Hell, if I walked in with my own 52 card deck and told you, I already picked my card and made you go through all 52 cards to calobrate the machine you really think you would know what card I picked ??

Anonymous said...

The "comments" are a perfect example of why polygraphs should be banned. The fact that even after you explain clearly to people that this machine is junk science, total bunk, and that lies cannot be detected by ANY machine and that it has NO BASIS WHATSOEVER IN SCIENTIFIC FACT... People still go, "well I guess they should do more research." What a bunch of DENSE IDIOTS. That is why these fake machines are still around, because people are very slow about understanding SCIENTIFIC FACT.

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