Lie Detector not reliable

Post by **sbp** » Sun Oct 20, 2002 1:25 am

http://www.sltrib.com/10102002/nation_w/5766.htm

snippage: WASHINGTON -- The National Academy of Sciences declared this week that polygraph examinations are dangerously unreliable and the federal government should cease depending on them to screen for security risks.

The academy's 18-month, federally-funded study found that the so-called lie detector not only incorrectly deems large numbers of people who are telling the truth to be liars, but may have allowed spies and others posing security risks into sensitive positions because they were able to pass polygraph tests.

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I'd be lying if this was a surprise.

So-called lie detectors are notoriously inacccurate, yet this myth about them being so great persists.

Tomuchtime · Post by **Tomuchtime** » Sun Oct 20, 2002 3:10 am

I'm not suprised at all.
Thanks.
bill

Post by **FlyingPenguin** » Sun Oct 20, 2002 8:57 am

It's why they're not admissable in court. Someone who's properly prepared can beat one. Also, a lie detector won't work on someone who truly believes he's not lying (like many pathological liars).

JonasWorld · Post by **JonasWorld** » Sun Oct 20, 2002 10:24 am

I'm scheduled to take one at the end of the month, and I'm nervous as hell to do it. I'm applying for a fed job that requires it. I really don't have anything to hide, I messed up once or twice as a kid, nothing serious.

A buddy of mine was applying for a police officer job and had to take one. He failed it because the administer of it thought he was lying about dealing drugs in the past six months. I know for a fact that this friend of mine has never even seen or taken any drugs his whole life.

Karchiveur · Post by **Karchiveur** » Sun Oct 20, 2002 1:44 pm

Meh.... can't you just convince yourself its the truth, I think it runs off, your brain pattern (like if your nervous or calm)
______________
Calm» being truth
Nervous» Being Lie

Post by **FlyingPenguin** » Sun Oct 20, 2002 2:35 pm

Polygraphs measure physical manifestations of indications of nervousness (pulse, respiration, electrical conductuctance of you skin as well as other factors).

It's much more sophisticated than this simple explanation, but essentially it's looking for involuntary signs of nervous. Most normal people will have a large change in several indicators if they're trying to conceal something.

The problem is that in order for it to work properly, a properly performed polygraph requires a LONG time to establish normal indicators. Most people are nervous the first few minutes so the first bunch of questions are just to get you comfortable. After that you answer a set of questions that have known answers so they can establish a baseline. Later on the more important questions are brought up interspersed with normal and less important ones.

The problem is that there's no light that comes on and says "LIAR". The polygraph interpretter has to go through the charts and compare your baseline responses to the important questions. It's very subjective and there's room for error. There are also good polygraph techs and bad ones.

People who have more of a concience that others are more likely (in my opinion) to get false positives. Also how you interpret a question is important. Have I ever stolen anything? Well hell yes, I shop lifted when I was 9. Is that pertinent to today? However a person with a concience may go in feeling guilty about that and thus any question about theft may elicit an emotional response because of it.

Meanwhile a compulsive liar (some who truly believes their own lies) would have no problems.

Worse thing you can do is to take any kind of tranquilizer or sedative before you take the test. Go in there nervous as all hell and just answer the questions. You are entitled to know the results of the test and if you disagree with them you should demand to be retested.

TheSovereign · Post by **TheSovereign** » Sun Oct 20, 2002 5:58 pm

@ MIT they have a 100 percent proof type test

scenario: a mass murder is comitted 4 people are dead and its @ a estate in beverly hills

the suspect claims hes never been their or seen those people before

so they attach probes to his head and show him random pictures of diffrent rooms in houses
then insert a room of the murder house in those pictures

if the brain changes its repsonce for the picture it has recognized it from memory and has an associated emotion

unless you lied it would never give a false responce
tsk tsk its a shame when your brain fingers you