Wednesday, October 31, 2007

Lie Detectors?

I’ve always been very curious about the concept of lie detectors. One Christmas when I was in my early teens I got a Radio Shack 150 in one electronics kit. It was a big board about 11”x17” that had all sorts of electronic pieces mounted to it. Next to each piece there were two springs. Also included in the kit was a big mess of wires and a book with 150 schematics. The idea was you looked at the schematics and placed you wires in the little springs and you could build what ever you liked. The most complicated project in the whole book was a “Lie Detector”. I bypassed all of the other schematics and went straight for the big one. After about a day of insert tab a into slot b and so on I finally had it complete.
The input from this device was two bare wires taped to my forearm about an inch apart. The output was a simple analog meter set to measure the skin resistance. It operated on the premise that people sweat more when they lie. The wires measured this galvanic skin response and the meter showed you the results. I was very disillusioned with this device. I tried it on many members of my family and was only to get and ever so slight change in the needle. I had grand visions of strapping it on my brothers and asking them, “Now were did you hide my legos?” and getting instant confessions, just like Wonder Woman’s golden lasso.
Later on I realized the “real” lie detectors measure several different things that are believed to be associated with lying; heart rate, blood pressure, respiration etc. These many measurements make up the modern polygraph test.
It didn’t take me long to figure out that the polygraph was better described as a nervousness detector than a lie detector. If somebody could control all of these factors then they could “pass” a polygraph test even though they many be lying. On the other hand if a certain subject provokes a nervous response then the subject could fail the test. What would happen if a person who was a victim of child molestation years earlier were accused of committing child molestation? I dare say that the question alone may cause enough nervousness and stress to fail the test.
Later on in life I learned that in some states it is ground for a mistrial if the phrase “lie detector” is ever used in a trial. Many states are realizing that it does no such thing.
This week on NPR they have been running a three part series on detecting lies. I found it very eye opening that in the final episode they referred the research of Dr. Paul Ekman who I have blogged about several times in the past. I doubt that a device that accurately detects lies will ever truly be developed. In fact I've come to realize that this device is not modern at all an it is more closely related to folk magic like dowsing and palm reading than it is to any real science.
So in the future if I ever decline to take a polygraph test please know that it is not because I know that machine works and I am afraid of having the truth revealed. It is because I know that the device is little more than witchcraft and I don't trust the results at all.

If you are interested in learning more about the controversy around the “polygraph test” check out the following links.
NPR Episode 1 Episode 2 Episode 3

1 comment:

  1. One of the things I learned about Ekman in a psychology class, is that a "lie detector" is being developed based on his theories. Supposedly, when someone lies they make involuntary muscle movements in their face. The lie-detector can detect the electronic impulses in facial muscles that cause these microexpressions. Even someone that has been trained to avoid making such muscle movements cannot suppress the initial electrical signal that gets sent.

    I have my doubts, though, about how effective this new device will be. I believe that people can convince themselves they are telling the truth, even when they are lying, which would render such a device useless.