Are polygraph ("lie-detector") tests reliable?

[Jack Hays]

There is no scientific evidence to demonstrate that polygraphs work at all.

It's basically psychological trickery, and an opportunity to grill someone.

As I said, in the hands of a skilled operator it's very effective.

 

[Gimmesometruth]

Sorry, but you're not credible.

Again, Jack, I'm not the data, nor are you, the data says you are wrong.

That is all.

 

[Visbek]

APA: "Most psychologists agree that there is little evidence that polygraph tests can accurately detect lies."

The Truth About Lie Detectors (aka Polygraph Tests)



2002 NRC study: Polygraph Testing Too Flawed for Security Screening (a mega-study on polygraphs)

"Polygraph testing now rests on weak scientific underpinnings despite nearly a century of study, the committee said. And much of the available evidence for judging its validity lacks scientific rigor. "

Home | The National Academies of Sciences, Engineering, and Medicine | National-Academies.org | Where the Nation Turns for Independent, Expert Advice


1991 study: Science and the CQT polygraph

"...because there is no way to determine the cause of a subject’s fear or anxiety, validation is impossible."

Science and the CQT polygraph - Springer


Unsurprisingly, pretty much every pro-polygraph article was published by, wait for it... Polygraph, a journal operated by the American Polygraph Association. What a surprise.

 

[Visbek]

As I said, in the hands of a skilled operator it's very effective.

It's effective at getting the subject to talk, and detecting typical signs of anxiety (sweating, increased heart rate etc). It's not effective at determining whether their statements are true or false. (See post above.)

 

[Casper]

Are polygraph ("lie-detector") tests reliable?

Know people that told the entire truth but were so nervous they were told that they were being deceptive and know others, including myself, that have lied on one and passed with flying colors, it is a matter of how one handles stress and testing, some are simply not very good at it.
They are not permitted as evidence and even our Congressmen are not willing to submit to them, they might help take the heat of you in an investigation but they can also have the opposite effect if they feel there is any sign of being deceptive even though you may have been honest. I would also add that many attorneys will also advice against taking them and it is generally a good idea to simply refuse based on the fact that they are faux science.

 

[polgara]

I've supervised a dozen or so exams and taken eight (IIRC) in 40+ years, and in my experience it's a very effective tool in the hands of a skilled operator.

Good evening. Jack. :2wave:

Does a skilled operator also take body language into consideration, because it's often correct if the questioning goes on for any length of time... :shock:

"If you tell the truth, you don't have to remember anything." >Mark Twain

 

[Jack Hays]

APA: "Most psychologists agree that there is little evidence that polygraph tests can accurately detect lies."

The Truth About Lie Detectors (aka Polygraph Tests)



2002 NRC study: Polygraph Testing Too Flawed for Security Screening (a mega-study on polygraphs)

"Polygraph testing now rests on weak scientific underpinnings despite nearly a century of study, the committee said. And much of the available evidence for judging its validity lacks scientific rigor. "

Home | The National Academies of Sciences, Engineering, and Medicine | National-Academies.org | Where the Nation Turns for Independent, Expert Advice


1991 study: Science and the CQT polygraph

"...because there is no way to determine the cause of a subject’s fear or anxiety, validation is impossible."

Science and the CQT polygraph - Springer


Unsurprisingly, pretty much every pro-polygraph article was published by, wait for it... Polygraph, a journal operated by the American Polygraph Association. What a surprise.

It's effective at getting the subject to talk, and detecting typical signs of anxiety (sweating, increased heart rate etc). It's not effective at determining whether their statements are true or false. (See post above.)

Again, in the hands of a skilled operator it's very effective. You just made my point.

 

[radcen]

Skilled operator... skilled operator... skilled operator.

Does this mean I should still always refuse a polygraph because I don't know if the operator is skilled or not?

 

[Jack Hays]

Skilled operator... skilled operator... skilled operator.

Does this mean I should still always refuse a polygraph because I don't know if the operator is skilled or not?

If you are the subject your preferences will not be considered.

 

[Casper]

If you are the subject your preferences will not be considered.

Polygraphs are not mandatory, so preferences must be considered.

 

[radcen]

If you are the subject your preferences will not be considered.

Incorrect. I cannot be forced against my will to take a polygraph. The choice is mine and solely mine. Now, does this mean I should still always refuse a polygraph because I don't know if the operator is skilled or not?

 

[joG]

Are polygraph ("lie-detector") tests reliable?

From what I have read, they are generally relatively correct. But they can be fooled as well as not working on certain people. So, it might not be a good idea to do a hanging on the basis of the detector alone.

 

[Gaius46]

All a polygraph does is measure changes in a persons body which a human then interprets. The problem is simply being nervous about being tested can be interpreted as lying.

The SC has ruled that judges do not have to admit polygraph results into evidence. Judges can admit or exclude them as they see fit.

 

[Southern Dad]

Incorrect. I cannot be forced against my will to take a polygraph. The choice is mine and solely mine. Now, does this mean I should still always refuse a polygraph because I don't know if the operator is skilled or not?

Unless you are in the military, in which case refusal has the consequence of a nice stay in Ft Leavenworth.

 

[radcen]

Unless you are in the military, in which case refusal has the consequence of a nice stay in Ft Leavenworth.

I'll take your word on that, and given the military's rules that I am aware of, it wouldn't surprise me. I am not in the military, though. Not anymore. I was never in a position to test it when I was in.

 

[Visbek]

Again, in the hands of a skilled operator it's very effective. You just made my point.

"Skilled operator" has nothing to do with it.

Again: The claimed underlying mechanism is based on bad science, dating back to the 1920s. It presumes that anxiety (as indicated via a few physiological measures) will increase a) noticeably and b) instantly when someone is lying, and clearly that is not the case.

So-called experts at detection deception are generally full of it. They typically do no better than chance, and the best can only catch 60% of liars. Polygraphs apparently don't do much better. (e.g. https://www.psychologytoday.com/blog/spycatcher/201203/the-truth-about-lie-detection)

Therefore, a polygraph is effective only when you want to make your subject nervous while you grill them. It's ineffective if you are trying to detect lies or deception.

I also can't help but notice that you didn't link to a single study to support your claim that polygraphs are in any way reliable. Hmmmm.

 

[radcen]

"Skilled operator" has nothing to do with it.

Again: The claimed underlying mechanism is based on bad science, dating back to the 1920s. It presumes that anxiety (as indicated via a few physiological measures) will increase a) noticeably and b) instantly when someone is lying, and clearly that is not the case.

So-called experts at detection deception are generally full of it. They typically do no better than chance, and the best can only catch 60% of liars. Polygraphs apparently don't do much better. (e.g. https://www.psychologytoday.com/blog/spycatcher/201203/the-truth-about-lie-detection)

Therefore, a polygraph is effective only when you want to make your subject nervous while you grill them. It's ineffective if you are trying to detect lies or deception.

I also can't help but notice that you didn't link to a single study to support your claim that polygraphs are in any way reliable. Hmmmm.

It was on a true crime documentary, but I forget which one, where a cop admitted to using polygraphs only for the purpose of rattling the suspect. He knew they were bogus, but most low-education suspects don't know that.

 

[Visbek]

It was on a true crime documentary, but I forget which one, where a cop admitted to using polygraphs only for the purpose of rattling the suspect. He knew they were bogus, but most low-education suspects don't know that.

Indeed I know others involved in background checks who have said the same thing. Even many intelligent and/or well-educated people are clueless about polygraphs.

Plus, police will absolutely jump at the chance to get a suspect to answer questions, at length. It doesn't matter that they can't admit the polygraph results into evidence, because they can still use your answers to their questions in court.

Worse yet, in many jurisdictions they're allowed to lie to a suspect about polygraph results. Ironically, police can't lie about evidence -- but since a polygraph isn't admissible, I guess they can lie about it.

 

[cpwill]

The machine is undeniably reliable. The human interpretation of the results is less so, but still rather reliable, and still used by the US government when issuing a TS/SCI clearance, investigating government crimes, and other reasons. There are claims by some that the test can be fooled. I've never seen it done, but it may be possible under certain conditions.

Hannsen fooled the test, as I recall.

 

[Beaudreaux]

Hannsen fooled the test, as I recall.

I've heard that report, however, and I know this is going to sound CT, but..., I'm not sure the report was accurate, or if it was intentional misinformation to allow for plausible deniability for those in the FBI that he fooled.

 

[CycloneWanderer]

"Skilled operator" is just another way for the people selling polygraphs to make more money.

"Why yes, our product is extremely reliable and valid. Pseudo-science, you ask? Balderdash! Those results just didn't have trained, certified, experienced operators interpreting the results. If you buy our machine, we'll give you a discount on the training courses so that your operators have the skills to do it accurate, 200% of the time!"

 

[brothern]

The machine is undeniably reliable. The human interpretation of the results is less so, but still rather reliable, and still used by the US government when issuing a TS/SCI clearance, investigating government crimes, and other reasons. There are claims by some that the test can be fooled. I've never seen it done, but it may be possible under certain conditions.

Hannsen fooled the test, as I recall.

As you and Beaudreaux both could do as well. Visbek explains the misconception behind it. Back then, people believe the psychological and physiological where inextricably linked. Therefore if you monitored vitals (heart beat, blood pressure, sweat), you'd see a positive indication of lying every time someone lied vs telling the truth. What the 1920s got wrong is that there is no link, what-so-ever between physiological reactions and lying. It just doesn't exist.

Again: The claimed underlying mechanism is based on bad science, dating back to the 1920s. It presumes that anxiety (as indicated via a few physiological measures) will increase a) noticeably and b) instantly when someone is lying, and clearly that is not the case.

 

[Jack Hays]

Polygraphs are not mandatory, so preferences must be considered.

In some lines of work they are mandatory.

 

[Jack Hays]

Good evening. Jack. :2wave:

Does a skilled operator also take body language into consideration, because it's often correct if the questioning goes on for any length of time... :shock:

"If you tell the truth, you don't have to remember anything." >Mark Twain

A skilled operator is a keen observer.

 

[_Sal]

In the hands of a skilled examiner, yes.

I agree but would add impartial...skilled and impartial