Lie Detector Test, Validity

The polygraph is notoriously unreliable for detecting anything like mendacity. Professionals have always known this. There's an old saying that if you're guilty and are offered a polygraph test, take it. You have nothing to lose and there's a good chance you might beat it. If, on the other hand, you're innocent, refuse to take the test. It could easily go against you despite your innocence.

Good one MA. Polygraphs are inadmissible in Australian courts. Now I know why

Polygraphs are absurd. Some people are excellent liars and therein is the failure of those darned machines.

That's a lie! They DO work! I swear I'm telling the truth! Doesn't anyone believe me? Don't pay any attention to those scribbles!!! I NEVER lie! Help me!

Polygraphs don't detect lies. They detect certain things relative specifically to physiological changes in the body and brain, but "lies" - c'mon. It's 2005, not 3005.

In fact calling it a lie-detector test is really selling it as something it's not. A polygraph is perhaps a useful stress and emotional response indicator, but hardly reliable for verifying statements.

Re: Lie Detector Test, Validity


If that's the case Merry, shouldn't EVERYONE refuse to take the test thus indicating their innocence?

In an ideal world, Nick, yes. Prob is that in this world if you refuse, the powers that be immediately think that this is highly suspicuious and you have to work twice as hard to prove your innocence. But I think this thread is just a symptom of the fact that polygraph tests are losing their 1930s-1940s appeal and credibility. Back then everyone called them 'lie detectors' and believed that they really identified lies with nearly 100 percent reliability. Today they are largely referred to by their proper name -- polygraphs -- and people realize that all it is is really just a medical device which measures heart rate, blood pressure, perspiration rate and some other things all at the same time. 'Poly' means many, 'graph' means to measure. That's all it is and, as someone said, if you can control your sphinctre muscle, you can control what the polygraph is measuring.

In an ideal world, Nick, yes. Prob is that in this world if you refuse, the powers that be immediately think that this is highly suspicuious and you have to work twice as hard to prove your innocence. But I think this thread is just a symptom of the fact that polygraph tests are losing their 1930s-1940s appeal and credibility. Back then everyone called them 'lie detectors' and believed that they really identified lies with nearly 100 percent reliability. Today they are largely referred to by their proper name -- polygraphs -- and people realize that all it is is really just a medical device which measures heart rate, blood pressure, perspiration rate and some other things all at the same time. 'Poly' means many, 'graph' means to measure. That's all it is and, as someone said, if you can control your sphinctre muscle, you can control what the polygraph is measuring.

Scientists are currently developing brain scans to detect if people are lying, but they still base their conclusions on current polygraph machines, which is a tad methodologically flawed/ But, hey, that's psychology!

Not really that relevant, but just felt like adding it. YOu guys are right about polygraphs. Some people panick when tested or may feel angry at the question, and so will get a false positive. Likewise, your garden variety psychopath may pass any polygraph you gave him , because people with this condition aren't as easily aroused as other people and don't feel guilt.

But true psychopaths would not register a lie even when they are lying and this shows up on the machine. The questioners always ask the person to lie to check the readings and if the lies and truth ful statements register the same way then the results are deemed "inconclusive".

I think that the poly is just an interrogation tool!

If you register higher on the control questions than on the relevant questions you are deemed reliable. Supposedly, you can bit your tongue and/or think of something stimulating or even count backwards by say 6s when a control question is asked and then then just simply control your breathing for relevant questions in order to ensure a pass.

It is all about the fear of the machine and being incontrol over yourself verse allowing the interrigator to be in control!