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Why Lie Detector Tests Can’t Be Trusted (smithsonianmag.com)
272 points by pseudolus 27 days ago | hide | past | web | favorite | 190 comments

I took a polygraph twice for an NSA internship (TS/CSI Clearance). It's an interesting process.

In the first phase, you go over your security forms (SF-86 and related) in detail with your polygraph examiner. They ask a lot of detailed questions, sometimes including things you aren't legally required to disclose (drug use and foreign travel outside the listed time limits).

In the second phase, they hook you up to the polygraph and ask two series of very specific questions, one called "lifestyle" and one called "national security." Lifestyle questions include questions about drug use, possible crimes, etc., and national security questions include questions about foreign contacts, involvement in terrorism, etc. They're very specific, like "Are you withholding any information about your involvement with illegal drugs in the past ten years?"

About half the time (based on my discussions with other prospective interns), the examiner becomes convinced you're lying about one of these questions and really drills into you. Most of the polygraph examiners are past FBI or CIA interrogators, so they know how to make you very uncomfortable.

I was explicitly told that I failed my first polygraph (the examiner was convinced I used more drugs than I let on), but some of the other interns were drilled about crazier things, like contacts with foreign governments or involvement with terrorist groups.

If you're particularly desirable to the managers who're looking to hire you, they'll keep inviting you to take more polygraphs, and you'll eventually pass.

I ended up turning down the NSA internship for better opportunities after realizing that NSA folks are not the most fun people in the world to hang out with.

> the examiner was convinced I used more drugs than I let on

No they weren’t. They merely pretended they were convinced. It’s all part of the act to make you nervous.

Possible, but how can you know for sure, if you were not there?

The parent poster is correct. This is a standard practice for polygraph interviews. The pick one question, more or less at random, and double/triple/quadruple down on it until you break. Or don't.

I got "have you ever committed a crime" (and after a actually pretty cool conversation about filesharing vs recording songs off the radio with a tape recorder, I passed). A friend of mine got "have you ever had sex with animals." I don't think he enjoyed his experience quite as much.

Oh, man. I would so much rather get the animal question. For the crime question I'd just be sitting there reaching my brain about what level of teenage transgressions I'm supposed to come clean about...

Sadly, 'Fuck you and the horse you rode in on' would be an inappropriate response.

Entirely appropriate as you get up and leave. Seriously. There is no other appropriate reaction unless you're terrified of retribution because it's the USSR or one of the wannabes. Price of freedom, etc. etc.

I'd be throwing in the word "Traitor" if it were me, but only on the basis that it is absolutely true.

After being accused of sex with animals, it's still probably unwise to discuss fucking the high horse someone rode in on.

One of the nsa's biggest breaches was perpetrated by a guy who admitted to bestiality during his polygraph.

lol, you can’t just leave us hanging here

Correlation doesn't imply causation.

Technically, nobody can know for sure, even someone who was there cannot read minds. But I posit that it’s way more likely that it’s part of the standard intimidation technique used by basically every professional intimidator ever – i.e. pretend to be angry and convinced about the person’s guilt in order to get them to either confess or to break down.

Very similar to my experience, but different 3-letter agency. Two rounds. Lots of questions about drug use. I wasn't shy about it because I had had legal run-ins over it when I was young so I knew it was already out there. But examiner claimed that I was being evasive. My employer really wanted me cleared so I was coached a bit, told that unless I admit to being a spy it almost doesn't matter what I admit I have done, as long as I am truthful. I was invited back for a second polygraph. Lots more questions about drugs, some really bizarre things I had never heard of. I thought WTF, and just "admitted" to most everything the examiner asked me. He still said I was being evasive. I thought, this is stupid, it doesn't work at all, he's just guessing.

At this point, I assume the point of the process isn't to ferret out liars, but to ferret out people who were trained to pass a polygraph under stress, on the theory that such people are more likely to be spies. It's the only thing that makes sense given the scientific unreliability, the random unfounded accusations by interviewers and whatnot.

But maybe I'm being to generous.

Did you pass?

>If you're particularly desirable to the managers who're looking to hire you, they'll keep inviting you to take more polygraphs, and you'll eventually pass.

Now, I am no expert on these things, but something tells me that they are doing this wrong.

"All of your previous polygraph tests indicated to us that you couldn't be trusted as far as we could throw you, however your latest one clearly shows that you have suddenly become as honest as the day is long. Welcome to the team."

Polygraphs can be "inconclusive" many times. Especially if you the kind of person that is uncomfortable sitting still and breathing in the same rhythm for an extended period.

I wonder if you could get prosecuted or investigated for things you admit to during the interview. I also wonder if there's any sort of legal privacy requirement that stops the examiner or someone else with records access from spreading around information related to your examination. I'd warrant most people have gotten away with doing things that should've gotten them arrested.

Yes, you can be prosecuted for things you admit during a polygraph interview.

You can also be prosecuted for lying, since the polygraph examiners are federal investigators.

> You can also be prosecuted for lying, since the polygraph examiners are federal investigators.

That part is not true. Polygraph examiners are not sworn federal law enforcement officers. But they are happy to refer any of your admissions of guilt to federal law enforcement who may come ask you the same questions. Lying to them is a criminal offense.

Certainly not joe shmoe polygraph examiners, but I was under the impression that the NSA examiners are sworn federal law enforcement officers.

Now that I say that, though, I can't find a reference to support this.

NSA polygraph operators are not law enforcement officers. Lying to them is nonetheless a violation of 18 USC 1001. However, I am not aware of any case where anyone has been criminally prosecuted for lying during an NSA polygraph interrogation.

Wait, it’s illegal to lie to federal LEOs?

It's illegal to lie to the Federal Government period:


More precisely, it's a violation of 18 USC 1001 to lie about "any matter within the jurisdiction of the executive, legislative, or judicial branch of the Government of the United States" (with a couple of specific exceptions as given). Technically you don't even have to lie to a Federal official since the statute doesn't specify that; it just has to be a matter "within the jurisdiction" of the Federal government.

Keep in mind, however, that this is not reciprocal: The Federal government can lie to you with impunity.

I like to call this the "Martha Stewart Rule"


Considering lie detectors are inadmissible in court, probably not. Being the cause of further investigation on the other hand...

They do threaten legal action if you lie about something on your SF-86.

Lying about something on your federal forms would make you vulnerable to blackmail, so that would definitely be something that the investigators would try to turn up.

In my case, I was extremely open and honest with the main investigator that I was interviewed by, including the things I did during college with recreational pharmaceuticals. I told all my friends to just "tell the truth" about what they saw happen.

I think my biggest benefit there was telling the story about how I saw that kind of stuff tear lives apart, and turn people who had been best friends into worst enemies, and the negative follow-on impacts of what happens when you can't pay your rent, you can't pay your electric bills, etc... because you have this debt to someone else that suddenly must be repaid this afternoon.

Forgive me for asking if you are uncomfortable saying, but were they correct about your drug use?

I'm coming very close to being 100% eligible for my security clearness but some of those questions would be tricky for me right now.

I've often wondered if I could round 8 years up to 10 to pass a polygraph.

Depends on the position. For defense and intelligence agencies, they want to see that there's nothing "recent" (past few years) or "chronic" (borderline or outright addictive behavior). If you smoked pot or did cocaine 8 years ago very infrequently you should have no issues.

HOWEVER: law enforcement agencies are quite a different story and tend to be much stricter in their requirements. Some, like the FBI, have public drug qualifier policies you will need to meet [1] and there is no wiggle room (1 day short of 10 years and you're 100% ineligible). Some agencies do not publish this policy (i.e. Secret Service) and you have to guess whether you're eligible.

The most important thing to remember is that whatever you admit on these forms will be on record for review by any agency for the rest of your life. DO NOT try to give extract or estimated numbers of usage on your SF-86 unless they are exceedingly low numbers. You can be honest with your background investigator during the followup but there's no reason to commit those things to writing on a form that's likely to be easily accessible later on.

[1] https://www.fbijobs.gov/working-at-fbi/eligibility

Unless you used to have a serious meth or heroine problem I'd say you're fine. ;)

I was pretty honest about my drug use. The way they phrase the questions sometimes leaves you with a bit of doubt, though. Like, "How many times did you use this drug?" I'm not sure who keeps a really diligent record of how many times they do drugs at parties.

But, yeah, I tried to be as accurate as possible, modulo that doubt about how possible it is to accurately answer these questions.

At least when they interviewed me back in 1989, I was as honest with them as I could be about what I could remember, and I was honest with them about how much I couldn't remember.

I have no idea what the rules are now.

As far as I've heard, it is more about lying than past use (unless that past is a month ago and was a real bender). Telling them the truth about something that happened 9 years ago isn't likely to get you booted.

Just don't be inconsistent.

Me too. I'm interested to know when this was because I am reading between the lines and believe little has changed on the questions between when you did it and I.

At my time I was told that all interviews at a certain exit off I-95 in Maryland were done by FBI.

I expect several people reading your note might also have gone through this process and failed. Interested to hear if anyone has successfully retrieved transcripts using a FOIA request.

The key is just to answer honestly no matter what the question. Did you have sexy with a goat? If the answer yes, then say yes. They do not care. What they care about is you tell the truth with no reservation as it a sign you cannot be blackmailed.

The polygraph can't actually measure anything that can (with any reliability) indicate whether you're telling the truth or lying though. It's basically just a prop to try and stress the subject out and convince them that the examiner can tell what they're thinking. The examiner (really interrogator, calling it a "test" is too generous) will literally pick random things that they feel you're being evasive about and drill you on it, even if it has no relation to the truth!

What does admitting you had sex with a goat have to do with if the machine works or not? If I was not clear, they are looking to see if you can be blackmailed. They may know already you buggered a goat, or snorted a kg of the white stuff. They just want to know you will admit anything you have done as that is the key to make sure others cannot gain leverage over you.

When I graduated college, my first job was working for what was then the Defense Communication Agency (now Defense Information Systems Agency), in a job that required a successful Secure Background Investigation for a TS/SCI clearance, and I was told that the position required a lifestyle polygraph + random urinalysis.

I used this to my advantage on more than one occasion, when the gaming group I was with was a bit too casual with their use of certain recreational pharmaceuticals. I told them straight out that my job required a lifestyle poly and random urinalysis, and that if they decided to do that to me the next morning, then I would be totally giving up my friends to the examiners. That usually convinced them to be more careful.

Strangely, the government never actually gave me a polygraph or urinalysis test, ever.

Was this a high school internship? If so, I think we went to the same school system.

> questions about foreign contacts

This sounds unreasonably intrusive IMO. What if you have a couple thousand acquaintances and friends around the world?

it's all about context. You're not asking for a job at the local donut shop, you're specifically getting involved in an organization that preoccupies itself with threats to the nation-state, internal and external. Kinda makes sense that they'd be intrusive. I'm not sure what the line of unreasonableness is in that context. You have no inherent "right" to work for the National Security Agency.

It's the NSA, dude. They specifically want someone who'll be _their spook_. What makes you think they want Mr. Cosmopolitan who lunches with Erdogan's third cousin and breakfasts with the Pope? Nothing about it sounds unreasonably intrusive. The national security guys should be rightfully paranoid.

> What makes you think they want Mr. Cosmopolitan who lunches with Erdogan's third cousin and breakfasts with the Pope?

Maybe this person has a better understanding of what's going on around the world and how different cultures work, possibly speaks multiple languages, and it might be a good thing to welcome their knowledge instead of scaring them off?

Which is why they are interested in the applicant lying about those contacts.

The application will provide an opportunity to disclose foreign contacts.

It would be harder to persuade the same person about the evils of said cultures.

Look at current events and how relationships are assets and liabilities.

Having thousands of friends and acquaintances around the world may well be disqualifying for certain positions, and assets for others.

> What if you have a couple thousand acquaintances and friends around the world?

Then that's what you say in response to the question.

I have no idea why there is not an accurate calibration of polygraphs published. Here's a straightforward calibration:

Have the subject write down a random number from 1 to 1024. Perhaps this random number is assigned via a phone app. Have the subject put the paper in his pocket.

An maximally accurate polygraph will require no more than 10 questions to determine the number in the subject's pocket.

[However, I think we all know what the result would be, which is why nobody publishes a simple calibration like the above: It is not in an trained examiner's interest to expose the inaccuracy of polygraphs.]

Trying to keep a random number secret likely is less stressful than an actual lie. Even if lie detectors worked this wouldn’t be a great approach. My way is better, scrap them for parts and buy beer for whatever is left over.

> Trying to keep a random number secret likely is less stressful than an actual lie.

Which begs the issue: If a lie detector is accurate only for answers that are stressful, then it sure looks like we need a detector to figure out if an answer is stressful or not.

Or to put it differently, now you have two problems: Lie detection and stressful-answer detection.

Nevertheless, I concede that your beer detection plan is superior.

Indeed it occurred to me when I took my LDTs that the test's basic premise is: our machine detects stress responses, and our questioner assumes repeated stress coincident with the same answer equates to a lie. Stated outright like that, everyone can see the assumption behind the test is obviously, irredeemably flawed.

Therefore I too must concede that the beer plan is flawless.

What about if you keep it secret you get $1000

There's a bias in gaining value you don't have and losing value you already have. People are much more risk adverse when losing value, even if small. So you'd have to give them the $1k first, probably for performing some task. Put the money in their have, continue with the distraction test to let the value sink in. THEN if they fail they lose the money. And even then this won't fully match the risk aversion models, but it'll better simulate it. These things are hard to measure.

The goal isn't to detect lies; it's to detect which lines of questioning make you nervous.

Committing to answer "yes" to every question without registering it enough to even understand it would make your polygraph "fail" even if it actually worked well in real usage.

Lie detector tests rely on psychological intimidation. The testee invariably gives up compromising information over the course of the test, allowing the tester to apply leverage or outright coercion. If no useful information is divulged, the test is marked a fail and requires a repeat.

There's a wonderful scene in The Wire where they give a young thug a "polygraph test" by interviewing him in front of a copy machine and hit the copy button when he answers a question so that it spits out the message they preloaded into the machine "false." The thug looks crestfallen and tells them the truth.

For reference this is the scene:


Yes, exactly. Polygraphs are just a form of interrogation technique, disguised as "science". If the science was debunked, then the credibility of the machines would be questioned and the interrogation process would not yield as positive (if you can call it that) results. So the whole mystique of polygraphs must be guarded to keep up the facade of the lie detector's true capabilities.

I mean they have been debunked and anyone that Google's it knows it.

Doesn't mean they don't work as an intimidation tactic. Though most of the agencies that use them are probably filtering out a lot of good employees by putting them through a test designed to mess with them. Instead of focusing on whether the person has the skills needed for the job.

It's got to be pretty intimidating. Getting locked up in a room with the investigator, being told that you're not actually required to be there, but it will seriously jeopardize your chances of employment if you decide to leave or decline, etc. I'm sure it works well as an intimidation tactic, as you say.

People need jobs and are willing to put up with lots. Going through with a polygraph is likely just one of a number of the things that people in these industries have to put up with.

It is extremely intimidating. My interviewer decided that he was going to tear me apart and that he knew I was lying about something (I wasn't). He said he could only help me out if I admitted I was hiding something and told him why. I stuck to my guns, told him that I wasn't hiding anything, that I was sorry that it seemed like I was, and that I would be able to sleep soundly knowing I had been honest on my test, even if it appeared otherwise. He didn't like that a whole lot, but I told him I'd rather fail the process having told the truth than pass it having lied on it. Ended up leaving that job shortly after largely because I didn't want to do the polygraph. Fuck that noise.

I'd imagine it's also a good way to filter out non-sociopaths from the three letter agencies.

For the NSA/CIA, I imagine there is still doubt, even if you've looked it up. "Does the NSA know something everyone else doesn't [about lie detecting]?" is not an easy question to answer.

Even the name "lie detector" is a misnomer, polygraphs have absolutely nothing to do with "detecting lies". They just detect physiological changes during a line of questioning.

It's a good example of black magic.

In my experience, that's not how the session goes. All the questions are reviewed in advance with the interviewee; there are no surprise questions. The interviewer I worked with even mentioned which questions he wanted and expected lies to. Many of these were somewhat personal questions ("Do you live at X; Is your mother's name Y?"), but nothing overly invasive.

Granted, I did not participate in any polygraph sessions used for the purposes of information gathering; more to confirm information already in the open.

I had the "intimidation" kind of polygraph session when I was questioned by a couple of police detectives about a theft in a building where I was a security guard. Intimidation and threats. Like if you don't answer right we're headed to your place to search everything. They did not review the questions in advance; they did try to surprise me; there was no attempt at calibration. The lie detector seemed to be a prop. After the test one of them came to me and said "you passed" while looking at me closely like my reaction was just the last test. I laughed. I guess it was the right answer.

> when I was tested by a couple of police detectives about a theft in a building where I was a security guard.

Why did you agree to take the polygraph?

> Like if you don't answer right we're headed to your place to search everything.

If in the US they can't do that (w/o a court order which they would not get solely based on the way you are describing the situation).

> I guess it was the right answer.

The right answer would have been to not take the polygraph test at all and not to talk to them.

> Why did you agree to take the polygraph?

I wanted to keep my job. I didn't want the cops to find my weed (campus housing) and maybe get kicked out of college. Nobody had threatened to fire me and I may well have made the wrong decision. But I was very easy to replace and the condominium was full of paranoid rich people with lots of time on their hands.

How is this not a joke?

I get the comments that it's an "enhanced interrogation technique", but it sounds like it requires the subjects to be at least a bit intimidated by it. If someone pointed a dowsing stick at you, you wouldn't be the slightest bit intimidated by it, no matter how mean looking it was.

What kind of strange culture lets a prop straight out of a 50s sci-fi flick instill respect in people? And how they do it? Surely it can't just be the Hollywood movies?

Sorry for breaking out in a bit of a rant, but I seriously can't wrap my mind around how these things could possibly be useful.

If you've ever been personally interrogated by someone that knows what they're doing (police detective, etc), it's a pretty intimidating experience by itself - and completely fascinating because you realize it's completely a learned skill to do that! You may call me naive, but it really preys on your desire to tell the truth. I can understand how a "devoted" criminal can easily game the interpersonal exchange, but the average law-abiding person gets confronted with a lot of strange and conflicting emotions - desire to pursue the truth, desire to please, etc. A skilled interrogator is pretty amazing.

Now add biometrics. It's not like the polygraph is separable from the interrogator. It's a question of establishing a baseline and watching for deviations that gain significance based on experience and knowledge. The polygraph enhances the ability of the interrogator in terms of their access to biometric data of the subject, and ancillary to that is the intimidation factor that the subject feels knowing the interrogator may be more aware of your biometrics than the subject themselves.

The reason why we settled on the polygraph and not something else is because of William Marston. He invented the early polygraph after noticing his wife’s blood pressure rose when she was angry. He also created Wonder Woman who carries a whip that makes people tell the truth. In the 1930’s he wrote a book advocating for the use of the polygraph by law enforcement. Gillette hired him for an advertising campaign to “prove” they had better razors. The public started to believe in it’s effectiveness which allowed it to start coercing confessions.

We might as well be determining guilt and innocence with a block of Kryptonite or by flipping a batarang. It’s ridiculous that it is still allowed.

It's not the machine itself that's intimidating, it's the consequence of being caught lying and the accompanying loss of freedom or job opportunity.

Sure, but nobody chose a wizard's hat or a dowsing rod, so there must be some cultural significance to it completely beyond my understanding?

Sadly (and incredibly) this is not always true: https://en.wikipedia.org/wiki/ADE_651

"as much as US$60,000 each. The Iraqi government is said to have spent £52 million on the devices" - Wow and no one thought hey let's test this baby out before we buy a thousand of them?

They did test them. Dowsing rods work very well in unblinded tests. That's a big part of why so many people believe in dowsing.

I'm gonna have to call BS on that. Finding water accidentally is astronomically more likely than finding a bomb.

Unblinded tests mean that the tester knows where the bomb is. Imagine you have a bomb on a table. Someone brings a bomb detector over and when they point it at the bomb, it indicates that a bomb is detected. Point it away, and it stops. This is a very convincing demonstration if you don't suspect shenanigans.

Well, if losing the dousing stick test ends your career and sends you through months of more investigation, which may or may not include interrogation, you might take the dousing stick test more seriously.

The dumbest things about these polygraphs is that you're pretty much forced to lie if you want to pass. Some of the questions were vague and if you are a normal human being without a halo glowing on your head you would fail. Questions like "Do you love your parents?", "Have you ever spread gossip?", "Have you ever done anything immoral" (My interviewer specified watching pornography as something immoral).

Thankfully my interviewer was much nice and seemed to give me multiple tries, telling me that they might do another one later if I really failed.

Overall the interview process was OK. I guess the only invasive part was when they interviewed my neighbors in person without telling me. (When the FBI comes knocking on your door, you freak out)

I also turned down the internship because the pay was abysmal for IT. $15 an hour.

When the Secret Service came to interview my grandmother, that's when things got the most interesting for me.

So the story goes, they only did that because the Defense Investigative Service didn't have anyone who could do the job locally, and so DIS must have asked around to find out who could do the job for them. But DIS agents definitely talked to various friends from college and other neighbors I had over the years.

Apparently only my grandparents got the visit from the Secret Service.

> watching pornography as something immoral

Well, there goes everyone.

"I disagree with the premise of the question."

It's a yes or no question

And I still disagree with the premise of the question, and so therefore I automatically fail.


I don't agree with this rebuttal. Though it happens a lot, people often assume wrongly that everyone uses pornography. No doubt many do, and good luck to them.

But there is no need to make a majority into a universal here.

I passed a polygraph, I was untruthful and still passed. The person administering the test had done tbis for the FBI for 15 years. I had no special training.

I failed a polygraph. I was truthful and still failed. It cost me a job. Luckily I found a better job. So, thanks polygraph.

I have known multiple people who went through investigations including polygraphs for clearances. They were all told to be 100% honest and that it wasn't violations (within reason) that would hurt them...its not displaying "integrity". Those people were screened out for admitting to minor things like marijuana use etc. One's rejection read like some self righteous admonishment and said something like "You do not display the moral quality of character we here at <insert place> are looking for. We wish you the best in your future endeavors". They were told they failed the polygraph when they were being honest. Frankly if this is the hypocritical "quality of character" those places exhibit...people are better off avoiding them. The agencies/companies prove with their behavior they do not have the honesty and integrity they claim to look for and use these tools selectively. They reward lying and manipulating the system and punish honesty.

Ye, well, e.g. Ted Bundy passed a polygraph. And the Green River Killer did too. But hey, another dude, innocent of course, did not pass the lie detector when they were looking for the Green River Killer. Oops

ALdrich Ames passed a couple of polygraphs.

They only got him because other sources implicated him, and because his finances were notably out of whack for a government employee.


To the best of my knowledge, Ted Bundy was never polygraphed. You are correct about the Green River Killer (Gary Leon Ridgway) and the innocent man (Melvin Foster):


I've heard that they're not very useful with true sociopaths because they require you to be uncomfortable with lying.

Even then, unless they are coupled with a comprehensive psychological evaluation that could identify sociopathy, they could not be considered a useful tool (generously assuming that they have any truth-discerning usefulness to begin with).

A friend failed a polygraph. She handled money in a resturant and was a scrupulously honest person. She had a genetic health condition and it was probably responsible.

But they knew her character, and even though she didn't pass she didn't have any problem or lose her job.

Why were you taking a polygraph? Just curious.

Some jobs require it. Not even super-secret top-hacker men-behind-the-curtain type of operations.

If you wanna be a senior sys admin for bed bath and beyond, you 'll be probably getting one.

> If you wanna be a senior sys admin for bed bath and beyond, you 'll be probably getting one.

Huh. I was a very senior 'sys admin' type for an enormous retailer for over a decade, and polygraphs never came up for me or anyone else there.

Any idea why bed bath and beyond is into such a thing?

My guess is that throwaway's statement was hyperbole, and Bed Bath and Beyond isn't a literal example of an employer that requires a polygraph. Instead it was an exaggeration meant to show how common the practice is in his circles.

I was asked if I have taken polygraph tests, and if I am willing to take one. They didn't follow up with it, but they seemed serious about it.

That was for a contractor position, not regular employment.

PS. Also drug testing.

My guess would be. Some sys admin did something illegal (some sort of fraud or something). So management wanted changes to prevent that in the future. And the cover your ass move was "we'll use polygraphs on new people!".

> If you wanna be a senior sys admin for bed bath and beyond, you 'll be probably getting one.

How does that clear the Employee Polygraph Protection Act?


Wow. Never heard of a non-government agency using them.

Pretty clear sign of a messed up company culture.

And one that trusts unscientific methods just because others use them.

That's not the kind of company you want to get involved, ever. If they do that during _hiring_ ...

The 1998 Employee Polygraph Protection Act largely prohibited the use of lie detectors for employee screening by private companies.

Lots of gov't jobs require them for dealing with confidential info.

Not quite a pseudoscience but not so accurate as to warrant allowing a person's life to be upended as has been documented on many occasions [0]. Unsurprisingly, there's a history of the polygraph industry litigating against third parties that question the reliability of polygraphs [1].

[0] https://www.wired.com/story/inside-polygraph-job-screening-b...

[1] https://antipolygraph.org/

The polygraph is entirely scientific in the way it actually works: eliciting forced confessions under psychological coercion. However, for that coercion to be effective, the targets and the public at large must be convinced of a pseudoscientific idea that lies are detectable physiologically.

Hence the conflict between the promoters and the detractors, proving that it works would make it no longer work.

And how do we know whether a forced confession is true? False confessions do happen under other circumstances. Obviously, if the subject reveals something backed by evidence they wouldn't have known being innocent, that's one thing. But if we're using their confession as the evidence, then it's the same problem as any forced confession.

There's a great book called "The Memory Illusion" by Dr. Julia Shaw


It's very easy to get false convictions, and to make people believe false memories. There have been widely replicated experiments.

There are two different answers depending on who you ask.

The more ignorant will answer: it’s obviously true because they confessed. Nobody would confess to a crime they didn’t commit.

The more evil answer is: who cares? The public is reassured by a self-admitted criminal going to prison and I get re-elected.

Right, and both work until the conviction is overturned, the media makes a big deal out of it, and the Justice System is called into question yet again. Or it's not overturned, and someone makes a documentary followed by a dozen podcasts and online petitions. Which again calls into question how just the Justice System is, and how impartial a jury of your peers really is.

The Generation Why podcast will occasionally raise the point that if you try the same case more than once, you often get different results. Which really raises questions. Why didn't the judge allow certain information into the trial the first time, but another judge did the second time? How was the prosecution able to withhold information from the defense? Why on Earth did the jury find the defendant guilty despite no evidence tying them to the crime? Or in some cases, the opposite is true. How did the jury find the defendant innocent with that much evidence against them?

And the real perpetrator is never caught.

Not at all.

Any information you receive verbally from a single source is not very reliable regardless of how it was obtained.

> Bureaucratic usefulness, rather than any scientific validity, goes a long way toward explaining why the polygraph became a standard instrument of the American national security state.

In other words, it's pseudo-scientific bullshit.

meh. it's biometrics. How the data is incorporated into the subjective interrogator's experience and knowledge framework is where the weakness is. But don't blame the robot. IOW, the polygraph is just outputting data, the rigor of applying the data suffers from underdeveloped understanding, but if I were an interrogator I'd much rather have biometric data in my back pocket than not.

I've done a few and never failed one. Was told to clench my butt cheeks really hard to get a pass. Another tip was to put a drawing pin into your shoe and push down onto it with your foot as hard s you were able to tolerate. And if you search online there are a few other techniques you can use to ace the tests. Most interesting for me was being told I'd failed a test I was later told I'd passed. It's sheer madness.

> Most interesting for me was being told I'd failed a test I was later told I'd passed. It's sheer madness.

It's pseudoscience. They might as well have [measured the size of your head][1] to make their decision.

[1]: https://en.wikipedia.org/wiki/Phrenology

They often ask you explicitly if you know or have researched methods to defeat the polygraph. It's a lose/lose situation because most people have heard of such things or DID research out of curiosity facing taking a test, but admitting it makes you look bad. You generally don't get the chance to explain yourself, and if you do it just makes you look more guilty. The entire process is designed to give an excuse to arrive at the conclusions the entity administering the test wants to arrive at.

So, I would have totally failed the test repeatedly, because I would keep insisting on fully explaining the circumstances under which I had heard about the methods but not actively researched them.

And I would tell them to check my shoe and see that there is no thumbtack there. And check my cheek to prove that I'm not biting it in secret. And otherwise expose all the other methods that I know of, and prove that I'm not using any of them.

I'm sure that I would have frustrated the hell out of them, and they would have made damn sure that I always failed the tests, every time.

Q: Are you capable of defeating this test?

A: No.

The answer does not convey any information whatsoever.

At least on TV there are now pressure sensors in the seats to catch the butt-clenching thing.

For federal agencies, the seat pad is now standard. There are no public studies of its effectiveness. Regarding how the U.S. government attempts to detect polygraph countermeasures, see:


How is that even supposed to work?

A TV viewer thinks "How about butt clenching?", then one of the characters in the TV show articulates this thought and other gives a response. What actually the response is usually does not matter, because TV viewer already felt some connection with the show when that question was asked.


By making you believe that it works, like every other aspect of the process.

Then they're going to need to go with an electrical sensor of some sort. Some kind of EBG that could at least plausibly detect it.

Something that's kind of rough and uncomfortable would make the most sense, especially if you had to sit in some exact place for several hours. Discomfort would add to the stress.

You're lying, you're clenching your butt!

Polygraphs aren’t really used for lie detection. Think of it as a tool for an enhanced interview. It allows for the interviewer to have many more dimensions of straws to grasp at in assessing you. “Lies” are assessed as anomalous readings measured against control questions. This is something polygraphers are open about and inform you of the control stage during the start. Afterwards, it’s all really an internal battle. There’s even various stages cues wherein they might leave you in the room alone to fester in your thoughts. So really it’s not whether youre a liar or not, but more of having a consistent nature

It's the classic "I already know the truth and lying will only make your punishment worse" trick that most moms seem to pull at least sometimes

Knowing this, it seems like it would be very easy to throw them off your lying scent.

I've had a few experiences in my past that, when brought to memory, cause fairly large adrenaline spikes. Certainly, the memories increase my heart rate by just thinking intently about them.

In theory... couldn't you bring these thoughts to memory - at random? When asked about what you had for breakfast, for example. It would appear as an anomaly... But if you did that often enough, the interviewer couldn't trust the anomalies.

Sure if what you lied about is a big deal. The polygraph room is purposefully sound-dampened. I remember being able to abnormally hear more of my body (heartbeat, saliva, etc) in the room. What I'm getting at is that during a polygraph, it's very doubtful you're going to be daydreaming while undergoing a 4-5hr long interview lol. If you want to know how to 'cheat' the polygraph - I'll tell you.

There's no magic to it, you just have to really not give a shit about anything really. In the context of the US government, they want workers that are first and foremost, resilient to manipulation. Historically, the biggest traitors in the country have been money-driven, hence the emphasis on identifying huge debt areas. Such debt can be leveraged against people easily. The other thing to consider is, do you think they want someone that's too honest? What about in the scenario that you're being interrogated by a foreign agency, you're telling the truth but you're sweating balls. A polygrapher can latch onto these signs and use them against you. And someone that's emotionless and doesn't really give a shit about anything good or bad? Pass the polygraph with flying colors, have fun swaying someone that can't be bought off nor exempts guilt.

I'm fairly sure that you are required to take a lie detector to join the FBI, which makes me worry about the validity of all federal forensics. And now we're resuming executions...

If you're concerned about this, you really shouldn't read up on the actual "forensics" the FBI did in the past, like "hair analysis", because it will ruin your day:


Or "bite mark analysis" (don't google that, it will ruin your day as well).

Is there a proper response to this other than just banging your head against a desktop until you're blissfully unconscious? I can't think of any other response that would properly articulate my response to skimming that article.

You can ask the Phantom of Heilbronn once you find her: https://en.wikipedia.org/wiki/Phantom_of_Heilbronn

I am sure, she has valuable input, seeing she is a criminal mastermind who avoided capture for a cool 15+ years.

You should worry. Nearly the entire field of criminology is pseudoscience. Few techniques employed during the 20th century have stood up to scientific investigation which is because they were never developed scientifically in the first place. It's simply a veneer of science promulgated by those who haven't actually understood the scientific method.

They could probably double the accuracy by also adding in phrenology.


Aldrich Ames didn't appear to have any trouble passing his, but I can't help but think if they added some phrenology in, they maybe could have caught him.


There is a lot of great info on the subject at https://antipolygraph.org/

The site offers a >200 page free PDF that details the failings of polygraph testing and lists extensive countermeasures [0].

[0] https://antipolygraph.org/lie-behind-the-lie-detector.pdf

I passed my NSA polygraph, though it was uncomfortable. However my psych interviewer was able to get disqualifying info out of me using just technique.

It was only years later while reading a book about the Shin Bet (Israeli military intelligence), I recognized the way I was manipulated.

No hard feelings, after all I was telling the truth, and I probably would have hated the job anyway.

What sort of disqualifying info, if you don't mind my asking?

There were a lot of interesting questions in the psych interview, from porn use to romantic relationships and digital pirating...

And, just spitballing, I wonder if it's a crime to lie in the psych interview. I know it is during the polygraph, since the examiners are federal investigators.

Let's just say at the time I was a bit of a heavy drinker.

And the technique basically was to spend about 15 minutes having possibly the most uncomfortable conversation I've ever had about sexual relationships, pornography, sexual fantasies, etc. -- none of which they actually cared about. The intent was to make me as absolutely uncomfortable as possible. Then he moved on to a few quick questions about drug and alcohol use, which was such a relief, that before I realized what I was doing, I had answered fully and truthfully.

What's interesting though is that a failed polygraph reading isn't sufficient to charge someone with lying to investigators because they would have to prove a polygraph is correct beyond a reasonable doubt. Furthermore, they wouldn't ask you a question they already know the answer to. For example, if they ask you, have you ever done drugs in the past, you wouldn't be there if they already knew the answer was yes.

Can you elaborate on the way you were manipulated?

Oh come on! You're going to drop a book reference but not cite the book?? That's just cruel.

Every Spy a Prince


I was polygraphed back in 2015. They polygraphed me three times, and then said that I failed the question regarding unauthorized foreign contacts. It was a very bizarre experience. They would often repeat stuff like "Don't try to make anything happen or stop anything from happening. Got it!?" during the questioning. I remember having to sit perfectly still, with a pad under my bottom as well as under my feet.

Amusingly, before polygraphing me I was asked if I had "read anything online" about the process, to which I shrugged and said "Hasn't everybody?" The entire process is ridiculous.

I think part of the issue is that errors are not evenly distributed. There are many more false positives (detecting a lie when the subject is truthful) then false negatives. Most people assume errors are random, in this case they are not. Of course, this is combined with the other unreliability of the measurements make it close to a waste of time.


George Costanza: It's not a lie if you believe it.

Surely everyone knows first hand how much variation there is in the inner experience of telling a lie to realise that these tests are a sham.

If we want to detect recognition of something they deny, we can go directly to the brain: https://www.psychologicalscience.org/observer/detecting-dece...

Michael from VSauce already tried to countermeasure this method and failed.



Also just want to say this plainly. If you ever will take a polygraph in the future, you should read about it online even if you "have nothing to hide."

The usefulness of the polygraph is not to detect lies, but is to be used as a enhanced interrogation tool.

What drugs can you take to be able to cheat your way though a polygraph? Since polygraphs are based on producing anxiety I guess anxiolytics would work.

Would something like Phenibut suffice I wonder?

Many people can believe their own lies which I guess will likely complicate any physiological pattern they try to correlate with a lie.

Oh I get it, the title is a pun: the truth-telling machine itself is a lie.

I've always looked at the polygraph as not really a lie detector but more so as the person taking it believe their own statements or doesn't get nervous.

I see a lawsuit coming..

They write an article on polygraphs and do not mention Aldrich Ames?


tl;dr (and I don't think it's even mentioned in the article)

You can cheat a polygraph by flexing your anal sphincter.

More: https://www.youtube.com/watch?v=NsoI92BfmqY

Some polygraph setups will include a "butt pad" that you sit on that can detect your flinching.

I think it's interesting because it somewhat supports the claim. If clinching didn't work or help in some way, why bother including a motion detector under your backside.

Those who believe clinching works also believe polygraphs work (except when clinching)

Remove the clinching illusion and you restore the polygraph illusion to that group.

Right. I don't honestly understand any justification for the "defenses" described (at various websites). If the polygraph just doesn't work, why attempt any "countermeasures". The whole thing is kind of funny.

I think you're exactly right. The fact that the "butt pad" is there means that you have to believe that clinching would have any effect one way or the other. So the butt pad is really just part of the overage mirage.

Or imagine someone comes into take a polygraph and you search their shoes and find a tack. You can be pretty sure they came in expecting to tell some lies, and had a plan for "beating the machine".

You just need to show consistency

Imagining that I’m running gets my heart rate up, I can keep my breathing consistent, and the finest sensor detects perspiration changes on your finger which is the toughest but also a mental game.

Finally you need to consider the psychology of the tester or institution testing you. There are irrelevant questions that may not be yes or no questions, but its often more important for you to not be a free thinking paralegal expert and instead a soldier that complies.

So if the question is “have you illegal downloaded mp3s” the answer isn't “the consumer doesnt have the burden of knowing if the provider owns the copyright or associated license and copyright infringement only occurs if you share it” its just “no”, but if you can rationalize your compliance with the legal defense then it will be seamless to say “no” without showing an anomaly on the polygraph

Also congratulations you're a sociopath now, just focus on your breathing

Some questions will cause some people to panic regardless. "Have you ever had sexual thoughts about underage people? Yes or No."

Better to say No and fail the test than say Yes and show consistent polygraphs but still fail the clearance and position.

Lying to the investigator is worse. Ultimately getting a clearance depends on a judgement call from several people. Answering truthfully to a very open ended question like that is not necessarily a dealbreaker.

More targeted followup questions may be worse. Stuff like acting on impulses, doing stuff that you could be blackmailed for, seeking out materials, etc...

People see questions on the forms and think that answering yes anywhere means no job, but what they really want to know is if someone can get leverage over you to betray their trust and if you can show a good level of judgement and maturity.

yes, these are factors.

now lets address how the federal government exempted itself in being able to use lie detector tests for employment when we know it doesn't work

the point is that the rationale is flawed. "but muh blackmail" yeah the ENTIRE private sector wanted to use that excuse too.

Raises the question is No the 'right' answer? 'Yes [when I was 15]' is an entirely reasonable, and I suspect common, truthful answer, so saying No might make you stand out more, even though the obvious 'right' answer is to say No.

I hold out hope for (f)MRI.

There's some research into guilt measurement with fMRI [1] but it's very hard to test. When my lab tests fMRI thought identification, we need participants to write down exactly what they plan to think about for certain concepts (death, family, etc) and we need them to think about one particular strong memory multiple times. We know, or at least we believe we know, and the participant knows that we know, what they're thinking about. Anything else makes it hard/impossible to classify and won't be accepted in the literature.

Asking someone to pretend to lie in a lab environment, like say responding to "What's your name?" with the wrong answer on purpose, won't elicit the kind of arousal response we want to record like "Did you steal this car?". There's just not a good way to standardize and measure this kind of response without deceiving the participant - you might do some kind of social research on them and ask them questions they aren't prepared for, but understandably no IRB would allow that.

[1] https://academic.oup.com/cercor/article/13/8/830/328813

A problem with fMRI is that most of the software is crap, thus rendering the analysis unreliable.


There's a lot of hyperbolic claims being made in the article and these comments which seem unsupported by science. The answer to the question, "can polygraphs be utilized to draw out truth?", is a resounding yes:

>Notwithstanding the limitations of the quality of the empirical research and the limited ability to generalize to real-world settings, we conclude that in populations of examinees such as those represented in the polygraph research literature, untrained in countermeasures, specific-incident polygraph tests can discriminate lying from truth telling at rates well above chance, though well below perfection.


Although it is not a silver bullet, it certainly has its applications, especially if the person being interviewed believes it works. Thus, the polygraph test makes sense in questioning sex offenders, for example:


> Although it is not a silver bullet, it certainly has its applications, especially if the person being interviewed believes it works.

The whole premise of a lie-detector test is that they are marketed to end user and the public at large as being both accurate and "scientific." That they yield results better than chance isn't particularly relevant: they are not what the sellers and users of them claim they are. The conclusions drawn from the readings of the machines are only loosely based on anything scientific and depend heavily on the interviewer's own personal biases. Yet they determine the fate of people's lives all the time.

Most science isn't accurate, that's why it's filled with p-values. They're often only reporting the mere hint of an effect which allows them to distinguish between a control and experimental population.

Polygraphs are almost certainly not reliable enough to convict someone on, but it's not admissible in court. That doesn't mean it can't be used to help coerce a confession or help lead an investigation. And the fact that you won't face up to the extraordinary amount of evidence showing that it can be useful suggests stubborn ignorance on your behalf.

> The answer to the question, "can polygraphs be utilized to draw out truth?", is a resounding yes

So can tarot cards, and magic 8 balls. polygraphs are bullshit pseudoscience and 100% interchangeable with any other fake bullshit when combined with a experienced examiner and an ignorant/gullible interviewee

...but isn't the answer to the question, "Can the polygraph be used to coerce false confessions from innocent people?" also quite a resounding, "yes"[0]?

Glossing over or attempting to detract from the grossly negative consequences doesn't automatically arrive at the conclusion that it's resultantly a "good" thing.

[0] - https://www.innocenceproject.org/polygraph-tests-contribute-...

What is the use case for a test that can indicate that something is probably the truth or probably a lie when focused on specific incidents? _(According to the study, the reliability drops when used for screening)_

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