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New lie detector?
Topic Started: Sep 16 2011, 09:06 PM (328 Views)
CJ
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A very minor case of serious brain damage

http://www.bbc.co.uk/news/science-environment-14900800

So...apparently, a new lie detector has been developed, which uses a video camera, thermal imaging and a bunch of algorithms to try and work out whether someone is lying. It's all based on the subtle involuntary movements that we make when we express our emotions.

At the moment, this thing can correctly tell whether someone is lying in two-thirds of cases, but the researchers think they can improve it to make it 90% accurate. According to the article, this is similar to the polygraph currently used for lie detecting....but this is where the article begins to go off the rails. First of all, polygraphs aren't 90% accurate: it's actually about 61%, which is little better than guessing. Secondly, "90% accurate" is misleading, because in the real world, you would have the base rate problem. If you don't know what this is, I'll use an example to give you an idea:

Suppose this were used on 100 people, 10 of whom were lying, and 90 of whom were telling the truth. It's 90% accurate, so on average, it would show 9 of the liars to be lying, and one to be telling the truth. Of the 90 people who were telling the truth, it would, on average, correctly identify 81 of them as telling the truth, and falsely identify the remaining 9 as liars. In total, it would identify 18 people as liars.....but only 9 of these would actually be liars. The remaining 9 would be false positives, so really, if someone 'fails' the test, you could only be 50% sure that they were lying. To be 90% sure in this situation where 10% of people (the base rate) are lying, you would need a very good lie detector; say, one that was 99% accurate. If only 1% of people were lying, you would need your detector to be 99.9% accurate. As a result, when polygraphs are used in trials, they pick up a lot of false positives, and those people unfairly suffer the consequences of 'failing' the test.

Maybe I'm missing something, but I just can't see this being any different from the polygraph (except for being much less invasive), so, contrary to what the article suggests, I don't see it being at all useful to security services unless it's made at least 98-99% accurate. What do you think?
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Shiny Star
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Irrelevant but still relevant

I saw it on the news, seems interesting.
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CJ
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A very minor case of serious brain damage

Yeah. Probably just a scientific curiosity rather than a useful tool unless they can make it really good, though.

The problem is, these things don't detect actual lies as such; they detect the emotions associated with lying, like fear and distress, but those could just as easily be caused simply by being in the situation and fearing that you won't be believed.
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Shiny Star
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Irrelevant but still relevant

I love how the voice on the News was saying it, all boring. It does look interesting with all the feature and stuff though.
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CJ
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A very minor case of serious brain damage

lol, newsreaders :P .We have one who puts emphasis on every syllable, as though she were speaking to a bunch of 2-year-olds!
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