Lie Detection

Has technology ever been able to reliably discriminate between lies and truths?

Brian DunningBy Brian Dunning via skeptoid
Read transcript below or listen here

Screen Shot 2014-07-10 at 8.00.43 PMA lot of people, like police officers and gamblers, think they can tell when a person is lying. But what we’ve always longed for is hard data; testable, mechanical proof that a subject is telling the truth or lying. For a long time, the standard has been the polygraph machine. Unfortunately it’s also widely believed to be unreliable and to be inadmissible in a court of law, so today we’re going to look at the hard data to see what polygraphs can and cannot do, and what other lie detection techniques may be on the immediate horizon, and how they fare in comparison. So put out that fire on your pants, and sit back.

Polygraph machines haven’t changed much since the earliest versions were introduced at the beginning of the twentieth century. They combine readings of blood pressure, respiration, pulse rate, and skin conductance, graphing these out with moving needles on a paper scroll. The idea is that these readings will change based on your stress level as you tell a lie. Polygraph_animatedWhile that basic concept is sound, the problem — and it’s a big one — is that any real effect is lost under a sea of other variables. Not only can the subject manipulate all of those readings with simple actions (biting the tongue, poking oneself with a hidden sharp object or fingernail, or even clinching the anal sphincter muscle), but the results are highly dependent upon the interaction between the subject and the polygrapher.

A large part of a polygraph test consists of the presentation. The machine is intended to be intimidating, as are all the wires and sensors attached to the subject’s body; as are actions by the polygrapher such as marking with a pen on the scroll at mysterious intervals. The polygrapher always begins by making you feel that you are very easy to read; for example, by asking you to lie to an innocent question like whether you’re wearing blue jeans, and then looking at the results and reacting as if you are the most comically easiest person to read ever. Polygraph 818_225pxThe whole show is designed to make you anxious about lying; so that if you do lie during the test, your stress will hopefully rise high enough above the noise level to actually give a useful reading. If you go in knowing all of this, knowing that you’re not overmatched and that this is a fair fight, you’ve got a great chance of yielding no useful results, whether you have anything to hide or not.

But more than that, the reading of polygraph results is completely subjective. There was a famous case in 1978 of a man named Floyd “Buzz” Fay, arrested for a murder he had nothing to do with, and who was convicted based on a polygrapher’s analysis of a lie detector test. Fay’s appeal included reports from four other polygraphers who examined the same charts and concluded there was no evidence of any deception. Fay was ultimately released when other investigations found the true killer, and he then became a keystone of the fight against the use of polygraph tests in courts.

Fay was not the only data point. In 1983  .  .  .

MORE – – –

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Follow

Get every new post delivered to your Inbox.

Join 801 other followers

%d bloggers like this: