Polygraph Tests- Can we trust them?

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Polygraphs tests, or commonly known as a "lie detector" test, are often seen used in movies, television shows, and in real life. This produces the misconception that this test is a foolproof method to see if someone is lying. This test rests on the assumption that bodily reactions supposedly give them away whenever they lie. The test measures physiological signals that often reflect anxiety like blood pressure, respiration, and skin conductance. While this test usually does better than chance for detecting lies, it also comes with a high rate of false positives. False positives potentially put innocent people in jail, which is unacceptable. I think this is something that must be changed as we can't put innocent people in jail because some test, that is only occasionally right, said that they were guilty. This makes me question why the polygraph test is still in use at all because of its inaccuracy. The book mentioned that they use it to get confessions out of victims who think they got caught because the polygraph said they were lying. However, the book also mentioned that when people do not confess but the polygraph came out that they lied, everyone assumes they are guilty. I think this is something that needs to be eliminated from our justice system because of its inaccuracy.

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I too agree that our justice system should find a different way to determine who is lying. Before reading more about polygraph tests, I didn't realize how many false positives they produce. It would be interesting to know how many people are in jail or prison because a polygraph test determined they were lying.

I have also noticed how popular this test is in crime dramas and reality shows like Maury. I have always wanted to take one of these tests just to see if I could beat it as i have heard many claims of people being trained to beat them.

I agree that these tests should be ruled out. I am a person that gets very nervous when authority addresses me and I blush, sweat, and get a speedy heart. If i was put in front of a lie detector with detectives in front of me I guarantee I would be sweating up a storm and have a fast beating heart even if I was innocent

I agree with all of you, but just to point out, they do a base line test in the beginning. That serves as a proper foundation for the test, allowing for differences in normal heart rates of different individuals. It would be very interesting to take part in the test, and see how I fare. Speaking of falsifiability, in one episode of Lie to Me, The main character had an army officer take a relaxant that would keep her heartbeat stable at all times during the test, thus botching the results. I thought it was interesting.

I agree completely that this test needs to not bear as much weight as it does. It should still be taken into consideration but should not determine anything, just offer more evidence.

I also agree, but it should also be taken into consideration that guilty people can still lie and pass the polygraph test. This is possible by causing the readings to match what a normal lie would look like when they are doing the baseline readings. Poking yourself with sharp objects and causing yourself pain causes your "truthful" statements to show up with the same readings that the "lie" statements have.

The book? Which book?
With whatever faults you perceive due probably to your lack of detailed knowledge regarding how polygraph really works, there is just no better method of truth verification commonly available.

The National Acadamy of Sciences concluded from the research they reviewed that properly conducted polygraph examinations produced correct results significantly greater than chance (85% to 97% in scientific studies). Compared with voice stress analysis which has a verified accuracy rate actually less than chance.

Perfect? No it is not.
Valuable diagnostic tool? Absolutely yes.

I feel that polygraph tests aren't reliable enough for them to be used in convicting criminals. They don't tell if someone lies, they just see if there is a changes in blood pressure, and one can alter results by doing certain things during irrelevant questions. The number of false positive is too high to be trusted.

Good point. Not only is the machine occasionally incorrect, just giving the test can give a bias conclusion. For example, if someone is on trial but fails a lie detector test, how is one supposed to convince a jury of innocence? On the other side, if a person on trial passes the test, they aren't off the hook anyways. Not only is the test faulty, but its functionality isn't used properly. It's more of a scare tactic than anything else, that happens to measure if someone is stressed. It has a place to aid police, but the results lead to questionable assumptions.

From my point of view, if I were innocent in a crime committed by someone else, and was put up to this lie detector test, I would sweat and feel anxiety just because it's a stressful situation. Someone is getting blamed or a crime they didn't commit, and this little machine conducting heart-rate and such is supposed to prove whether you're guilty or not. I don't think this is a very healthy and proficient way to go about proving someone is guilty....or innocent.

I also think that it's super interesting that we place so much dependency on lie detector tests when they have been proven to be so inaccurate. However, I think that they are used because they make people feel better knowing that there is something authority figures can use to prove that someone is lying.
I think that it is unfair how those tests are run because there are a lot of people, including myself, who would get nervous simply by having to take a polygraph test. There are some people who sweat even when placed under small amounts of stress. I think that we should either completely eliminate using a polygraph test or that we should come up with a new way to detect lies.

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This page contains a single entry by vishn010 published on April 2, 2012 3:21 PM.

Emotional Darwin was the previous entry in this blog.

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