Freethought & Rationalism Archive

emphryio · 08-11-2002, 03:53 PM

It monitors the chest and stomach relative expansion and frequency, pulse rate and supposedly the amount of moisture from you fingertip. When hooked up to one, the operator usually demonstrates that it works by telling the "victim" to purposely lie. Then the operator shows the supposed "peak" on the readout paper showing the lie.

Does it actually detect lies? Yes or no plus reasoning if you like.

Personally I think it is absurd. Only people who erronously think it detects lies will be "forced" to tell the truth. (Which is good.) I find it depressing that everyone seems to believe in such an absurdity. Surely that can't be the case here?

The Lone Ranger · 08-11-2002, 04:26 PM

My understanding is that most people, when they're telling a lie and afraid of being caught, will experience an elevated heart rate and will start to sweat. Theoretically, an experienced operator can use this information to infer whether or not the person hooked up to the machine is telling the truth.

Even so, lie detector tests are notoriously subjective and unreliable, and I've frequently seen it claimed that anyone with a reasonable degree of self-control can defeat one without difficulty. On the other hand, an innocent but nervous person will often fail the test.

It is my understanding that they're considered so unreliable that few -- if any -- courts of law consider a lie detector test to be admissible evidence of guilt or innocence.

Cheers,

Michael

[ August 11, 2002: Message edited by: The Lone Ranger ]</p>

The Lone Ranger · 08-11-2002, 04:30 PM

Quote:

"I don't know anything about lie detectors other than they scare the hell out of people."
--Richard Nixon

You might want to check out the Skeptics Dictionary entry on polygraphs <a href="http://skepdic.com/polygrap.html" target="_blank">here</a>.

Cheers,

Michael

emphryio · 08-11-2002, 05:06 PM

Thanks Lone Ranger

Quote:

A DOE security contractor who administered a 1998 polygraph test to Los Alamos scientist Wen Ho Lee found him to be innocent of committing espionage, providing classified information to an unauthorized person, or intending to harm the United States. Unusually strong readings indicated an absence of deception. The test was reviewed by two additional polygraphers, who concurred with the finding. But then the Federal Bureau of Investigation (FBI) examined the very same data and concluded that Lee had failed the test.

This is what particularly worries me about lie detector tests. Obviously they don't detect lies, but who knows what the administer will say the results are? It certainly looks like the FBI lied about Lee's results. For this reason, if I was a suspect in a crime, I would be afraid to take a lie detector test, whether innocent or guilty.

Kachana · 08-11-2002, 05:15 PM

As far as my limited understanding goes, the most successful type of test is the Concealed Knowledge Test.

Let's say you broke into a house and killed someone, and your baseball cap with a batman logo on the front got lost in the process. The police recover the hat. You are one of the suspects (for whatever reasons), and you are hooked up to a machine monitoring various physiological statistics (don't know the details of the monitoring process) and are shown a series of slides.

Most of the slides are random pictures, perhaps including random articles of clothing, and a baseline 'physiological level' is established. Then they show you your hat which you know you lost at the scene. For most people who committed the crime and who's hat it was this would cause a large physiological reaction, heart beating faster, sweating and so on, if you had never seen the hat before, this would not be the case.

This doesn't seem absurd to me, certainly not perfect though, and whether it should be admissable in court is a different matter.

It's no different in principle from tactics we try in everyday life. Let's say you find the web address <a href="http://www.howtomakeabomb.com" target="_blank">www.howtomakeabomb.com</a> in your history folder, you may think to yourself 'Shit, who went there? It could be any one of my 3 sons. I doubt they'd fess up if asked politely, so I'll approach them separately and subtly make a reference to it in conversation'. If you did this, and one of your sons suddenly went bright red and started sweating at your veiled-bit-obvious-to-those-in-the-know reference, and your 2 other sons didn't even notice the reference, would it be absurd to think it most likely to be the son that reacted, out of the 3 sons?

emphryio · 08-11-2002, 05:28 PM

Quote:

David Lykken, emeritus professor of psychology at the University of Minnesota, is a leading critic of polygraphs and author of an influential book, "A Tremor in the Blood" (1981). He can hardly believe he still has to tell people that the polygraph isn't science.

"There's something about us Americans that makes us believe in the myth of the lie detector. It's as much of a myth as the Tooth Fairy," he exclaims in frustration.

Quote:

"It's tea leaves and witchcraft," said a senior U.S. intelligence agency scientist, who has long campaigned for the elimination of polygraph tests.

Anyway, for a job, I may be taking another one shortly. (I took one for a job about a decade ago.) Should I admit to the administer that I know there's no such thing as a lie detector? When I took one a decade ago, I felt my intelligence was rather insulted by the whole charade, but I kept my mouth shut and played along.

[ August 11, 2002: Message edited by: emphryio ]</p>

emphryio · 08-11-2002, 05:44 PM

To Kachana
What if two sons were present at the computer at the time the site was up? Mikey is looking at it taking notes. Johnny is standing behind thinking that Dad would be mad if he knew what his sons were looking at and saying, "Mikey don't look at that. We'll get in trouble."

Dad questions Mikey but he's an accomplished liar. Meanwhile innocent bystander Johnny gives the "guilty" response.

So a lie detector can be worse than insulting to a person's intelligence. It can wrongfully accuse someone of wrongdoing. (The links Lone Ranger gave have examples of this.)

SteveD · 08-11-2002, 06:14 PM

I recently took a polygraph test as part of the process for obtaining a security clearance. I had never taken one before.

The guy who was administering the test explained all of the theory of how the thing worked to me and then we went over all of the questions that he would be asking. As part of the series of questions were some that I was supposed to intentionally answer untruthfully. These were used to help calibrate the other answers. These were very innocuous questions such as "what color pants are you wearing?". They was absolutely no emotionally charged component to the calibration questions whatsoever. Furthermore, we practised the false answers to these test questions before the actually polygraph test.

I was amazed to see that the answers to these test questions did show a very significant reaction on the machine. Especially because I new the question was coming and new how I was going to answer it.

He also explained that they only considered a measured reaction to be significant if it was over 80% higher than the baseline. If my reaction to the deliberately false answers had been less than this then it would not have been considered a valid test.

He also stated that a high reaction to a question would not specifically indicate lying but only that there was some underlying stress and that he would then have to probe to figure out why the particular question was causing a reaction.

I was pretty surprised at how well it worked as I was pretty skeptical going in.

Steve

Bialar Crais · 08-12-2002, 12:21 AM

David Mills have a few things to say about <a href="http://www.geocities.com/forbidden_area/cess1.html" target="_blank">polygraphs</a>.

Personally, I'd say that polygraphs, in general, is about as reliable as flipping a coin. It does, in best of circumstances, detect nervousness, but nervousness is not a crime.

For instance, if you where hauled in to the police station and strapped to a polygraph and pushed around with a barrage of questions, woudln't you be a bit nervous? Hell, I would.

The calibration questions are quite silly as well. I mean, "You are supposed to lie. Answer htis, is your hair red?" won't exactly trigger any response, while as soon as the questions get backs to the crime nervousness may creep in. This is of course true for polygraph tests done to test candidates for jobs and whatnot.

Secondly. Getting away woth murder. Aldrich Ames, CIA agent, and seller of secrets to enemies regularily went through polygraph tests and where never caught.

Polygraphers reluctance to engage in real, scientific experiments to test the validity of their claims is quite telling as well IMHO.

In essence. No, I wouldn't trust a polygraph farther than I can throw it. And not being very muscular I wont throw it very far I wager

.

Secular Pinoy · 08-12-2002, 07:27 AM

<a href="http://www.antipolygraph.org/" target="_blank">http://www.antipolygraph.org/</a> has great resources for challenging the effectiveness of polygraphs. They even have an outstanding challenge against the polygraph community, and a timer counting the number of days since he issued the challenge, ala JREF.

I'm agnostic right now but leaning towards the polygraph-is-unscientific side.

08-11-2002, 03:53 PM	#1
emphryio Veteran Member Join Date: Oct 2001 Location: WV Posts: 4,369	Can a lie detector actually detect lies? It monitors the chest and stomach relative expansion and frequency, pulse rate and supposedly the amount of moisture from you fingertip. When hooked up to one, the operator usually demonstrates that it works by telling the "victim" to purposely lie. Then the operator shows the supposed "peak" on the readout paper showing the lie. Does it actually detect lies? Yes or no plus reasoning if you like. Personally I think it is absurd. Only people who erronously think it detects lies will be "forced" to tell the truth. (Which is good.) I find it depressing that everyone seems to believe in such an absurdity. Surely that can't be the case here?

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08-11-2002, 04:26 PM	#2
The Lone Ranger Veteran Member Join Date: Oct 2001 Location: Eastern U.S. Posts: 1,230	My understanding is that most people, when they're telling a lie and afraid of being caught, will experience an elevated heart rate and will start to sweat. Theoretically, an experienced operator can use this information to infer whether or not the person hooked up to the machine is telling the truth. Even so, lie detector tests are notoriously subjective and unreliable, and I've frequently seen it claimed that anyone with a reasonable degree of self-control can defeat one without difficulty. On the other hand, an innocent but nervous person will often fail the test. It is my understanding that they're considered so unreliable that few -- if any -- courts of law consider a lie detector test to be admissible evidence of guilt or innocence. Cheers, Michael [ August 11, 2002: Message edited by: The Lone Ranger ]</p>

08-11-2002, 05:15 PM	#5
Kachana Regular Member Join Date: Oct 2000 Location: Bristol, UK Posts: 279	As far as my limited understanding goes, the most successful type of test is the Concealed Knowledge Test. Let's say you broke into a house and killed someone, and your baseball cap with a batman logo on the front got lost in the process. The police recover the hat. You are one of the suspects (for whatever reasons), and you are hooked up to a machine monitoring various physiological statistics (don't know the details of the monitoring process) and are shown a series of slides. Most of the slides are random pictures, perhaps including random articles of clothing, and a baseline 'physiological level' is established. Then they show you your hat which you know you lost at the scene. For most people who committed the crime and who's hat it was this would cause a large physiological reaction, heart beating faster, sweating and so on, if you had never seen the hat before, this would not be the case. This doesn't seem absurd to me, certainly not perfect though, and whether it should be admissable in court is a different matter. It's no different in principle from tactics we try in everyday life. Let's say you find the web address <a href="http://www.howtomakeabomb.com" target="_blank">www.howtomakeabomb.com</a> in your history folder, you may think to yourself 'Shit, who went there? It could be any one of my 3 sons. I doubt they'd fess up if asked politely, so I'll approach them separately and subtly make a reference to it in conversation'. If you did this, and one of your sons suddenly went bright red and started sweating at your veiled-bit-obvious-to-those-in-the-know reference, and your 2 other sons didn't even notice the reference, would it be absurd to think it most likely to be the son that reacted, out of the 3 sons?

08-11-2002, 05:44 PM	#7
emphryio Veteran Member Join Date: Oct 2001 Location: WV Posts: 4,369	To Kachana What if two sons were present at the computer at the time the site was up? Mikey is looking at it taking notes. Johnny is standing behind thinking that Dad would be mad if he knew what his sons were looking at and saying, "Mikey don't look at that. We'll get in trouble." Dad questions Mikey but he's an accomplished liar. Meanwhile innocent bystander Johnny gives the "guilty" response. So a lie detector can be worse than insulting to a person's intelligence. It can wrongfully accuse someone of wrongdoing. (The links Lone Ranger gave have examples of this.)

08-11-2002, 06:14 PM	#8
SteveD Regular Member Join Date: Jan 2002 Location: California Posts: 118	I recently took a polygraph test as part of the process for obtaining a security clearance. I had never taken one before. The guy who was administering the test explained all of the theory of how the thing worked to me and then we went over all of the questions that he would be asking. As part of the series of questions were some that I was supposed to intentionally answer untruthfully. These were used to help calibrate the other answers. These were very innocuous questions such as "what color pants are you wearing?". They was absolutely no emotionally charged component to the calibration questions whatsoever. Furthermore, we practised the false answers to these test questions before the actually polygraph test. I was amazed to see that the answers to these test questions did show a very significant reaction on the machine. Especially because I new the question was coming and new how I was going to answer it. He also explained that they only considered a measured reaction to be significant if it was over 80% higher than the baseline. If my reaction to the deliberately false answers had been less than this then it would not have been considered a valid test. He also stated that a high reaction to a question would not specifically indicate lying but only that there was some underlying stress and that he would then have to probe to figure out why the particular question was causing a reaction. I was pretty surprised at how well it worked as I was pretty skeptical going in. Steve

08-12-2002, 12:21 AM	#9
Bialar Crais Regular Member Join Date: Feb 2002 Location: Lule�, Sweden. Posts: 354	David Mills have a few things to say about <a href="http://www.geocities.com/forbidden_area/cess1.html" target="_blank">polygraphs</a>. Personally, I'd say that polygraphs, in general, is about as reliable as flipping a coin. It does, in best of circumstances, detect nervousness, but nervousness is not a crime. For instance, if you where hauled in to the police station and strapped to a polygraph and pushed around with a barrage of questions, woudln't you be a bit nervous? Hell, I would. The calibration questions are quite silly as well. I mean, "You are supposed to lie. Answer htis, is your hair red?" won't exactly trigger any response, while as soon as the questions get backs to the crime nervousness may creep in. This is of course true for polygraph tests done to test candidates for jobs and whatnot. Secondly. Getting away woth murder. Aldrich Ames, CIA agent, and seller of secrets to enemies regularily went through polygraph tests and where never caught. Polygraphers reluctance to engage in real, scientific experiments to test the validity of their claims is quite telling as well IMHO. In essence. No, I wouldn't trust a polygraph farther than I can throw it. And not being very muscular I wont throw it very far I wager .

08-12-2002, 07:27 AM	#10
Secular Pinoy Veteran Member Join Date: Feb 2001 Location: Quezon City, Philippines Posts: 1,994	<a href="http://www.antipolygraph.org/" target="_blank">http://www.antipolygraph.org/</a> has great resources for challenging the effectiveness of polygraphs. They even have an outstanding challenge against the polygraph community, and a timer counting the number of days since he issued the challenge, ala JREF. I'm agnostic right now but leaning towards the polygraph-is-unscientific side.

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