11/06/2008

Jeremy Kyle and the Lie Detector Test

I would like to make it perfectly clear that I hate, with a passion, talk shows. Why these people need to use television as a medium to air their laundry is beyond me. I know lots of people want to be on the TV, but I wouldn't want to share anything that personal, and generally anything that embarrassing/pathetic, with the world at large.

But that's not the aim of today's rant. No, today we focus on that Jeremy Kyle staple, the lie-detector (aka polygraph) test. There is much argument on the reliability of these tests, generally somewhere between 60% and 97% is quoted (however a great deal of this evidence is unreliable).

The physiological effects recorded by the polygraph are not unique to deception. Surely this should set off alarm bells?

Well no, these people on what seems to be a daily basis put major decisions in the hands of a machine which is at best 97% accurate. Kyle is guilty, as others are, of making this seem almost infallible.

What I do in a situation like this is turn the statistics around. 97% accurate means 3% inaccurate. For every 100 tests done, 3 (on average) will give the incorrect result (remember that this is the best case scenario!).

If you were a jury member would that be accurate enough for you to convict? If you were a judge would you accept that if the average accuracy of the evidence before you was 97% then for every 100 people you convicted 3 would have been denied their freedom for no reason at all. I hope not.

Innocent people will unfortunately be imprisoned under any system of law and order we have, as a species, yet envisioned. But for me the number of innocents convicted would have to be, as a minimum, somewhere around 1 in 10,000 (99.99% accuracy). If the evidence was any less convincing than that I would, personally, have to call that reasonable doubt.

But Kyle commits a worse sin. An inconclusive test is just that, it is impossible to draw a conclusion from it. Yet the daytime demigod, facing four possible thieves who had undergone the polygraph, three of which got an all clear and one of whom got an 'inconclusive', picked on that 'inconclusive' person as the culprit. An inconclusive result, even given the fact that the others pass the truth test, does not mean that person has failed to tell the truth, it means that the test has failed to discriminate.

Of course this would require Kyle, the juror/judge, the people on the show, etc. to have a sound basic knowledge of mathematics and scientific reasoning. Which given the fact we live in the Jeremy Kyle generation is sadly unlikely.

5 comments:

George said...

The only ones claiming a high accuracy rate for polygraphic lie detection are those making money from this pseudoscientific procedure. The consensus amongst scientists is that polygraphy has no scientific basis. See AntiPolygraph.org for a thorough debunking of the lie detector.

Zebra said...

Saw an ad online in the UK advertising lie detector tests for potential employee's!! Scary. Basically if you are nervous while answering a question it will come out showing you've lied. That's really all these tests do - they test nervousness. Personally I become nervous when I suspect someone wants to show me up as a liar so therefore I wouldn't come out looking too good on a lie detector test as the worry of the result would actually produce a bad result. I also saw a documentary where a US detective said he & his colleagues tested the polygraph themselves & found if they were nervous answering then their answer came out a lie, when they hadn't lied & conversely when they did lie they found if you squeezed your in your buttocks, as if trying to hold in flatulence, then your lie was not detected in the test! I'm not kidding, they seriously discovered that is the way to fool the test when you're lying.

As for the Jeremy Kyle show, has anyone on it, whereby he accused them of being a liar re the polygraph test, actually pointed out to him that these tests are inaccurate? Have they ever said, by the way Jeremy, have you ever done one yourself? Are the people they choose to have on this show seriously that ignorant? And likewise with the audience who seem to have total faith in the test results even though it looks to me that genuine honest guests, have come out looking like liars? Same thing with that Moment Of Truth tv show where contestants have to come out as telling the truth on a lie detector test in order to win big cash prizes. Alot of people have been caught out on some silly questions where you could see it was unlikely they would lie about that particular thing. For instance, one guy lost a fortune through being shown as a liar on this ridiculous question that sure no one would bother lying about as it's not even a big deal. "Have you even stuffed anything down your pants to make your penis look bigger?". He answered "No" & the lie detector said this was a lie, so he lost all the money. The guy was stunned. I mean if it was true of course you would just answer this question yes & then make a joke of it, saying you did this once as a joke with friends or for a school comedy play or something. Given that this guy had answered truthfully, owning up to far more contraversial & embarrasing things than this, I believe he had not lied when answering that silly question. I've seen this happen many times on this programme. It's a shame as evidently much of the population are unaware that lie detector tests are so bogus.

Adam said...

Another constant annoyance of mine is his faulty logic in interpreting the results. I'm not sure whether he genuinely hasn't cottoned on to the fact that his logic is completely flawed, or whether he does it to play up to the crowd.

Assume a person is asked 3 questions. They pass the first and fail the second two. They protest and claim that the lie detector is wrong. Kyle's standard response is "well if the lie detector is wrong, why did you pass the first one?"

One could flip a coin 3 times and justify the results with the same argument - it wouldn't make for an accurate lie detector though.

It got some of them "right" i.e. it agreed that you were telling the truth. You assert that you were telling the truth and therefore the lie detector must have got that right, and therefore must have got all questions right, and therefore must be entirely accurate.

We can all see the absurdity of using a coin flip to determine the result yet this logic would justify the same.

Luverly Lolly said...

Jeremy Kyle is using the Polygraph tests as accurate, whereas experts do not agree that they are. Kyle knows this, but is making a fortune misleading people & brow beating some of the guests he feels are lying. He is an expert @ getting the audience on his side, but most people watching his flawed show can see him for what he is, an 'agony aunt' The
people interviewed generally appear to be of a poor standard of education, unable to speak the language of their own country properly that the fast talking Kyle
manipulates. It's amazing that he gets away with using the same words throughout the show. 'Gimme a break. It's about time it was dumped & something else with more
'grown up' was presented.



Havursay said...

I wouldn't describe JK as expert at anything with regard to this awful tv programme. He has single handedly brought British Television to a new low regardless of viewing figures. He is inadequate as a mature adult interviewer and irrelevant in all other respects. Using his name in the third person over and over, trying to look masterful as he repeatedly hitches up his only pair of pants, (surely that suit stinks by now) whilst referring to guests and viewers alike as "my friend". Interesting and educated serious programme and documentary makers have become national treasures while JK surrounds himself with chavs and wasters, and the reason? This is about the intelligence level of this obnoxious little TV parasite.

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