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Comment by LatteLazy | Hacker News Reader

Ah yes, polygraphs, long proven nonsense and not used in virtually any other western country. I wonder how he beat that?

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Aren't they essentially just glorified galvanometers like the Scientology e-meter?

Pretty much. They also do heart beat and a bunch of other things. Then (like a scientologist) the operator "interprets" that you're lying or not.

Yes, and I built a very simple one in law school, to illustrate the concept (well to be honest I was an engineer who went to law school as a hobby, and then I took every excuse I could find to build technology things as a hobby within a hobby). Anyway it was just a multimeter, some washers soldered to copper wire and some tape to keep the washers in their place on the subject's hands. When people didn't try to game it, it actually sort of worked, although I have no proof of statistical significance; I just had a feeling of 'better than random'. (our experiments were more focused on how to ask questions to elicit the highest response, as questioning with a polygraph requires some skill at asking questions that are leading or not, and in just the right ways).

Conclusion is still that it's nowhere near reliable enough to be used for anything, but the principle that people show physiological responses when answering truthfully or not about things is sort of true (I don't think that was ever under debate, still was a fun experiment).

Just a guess, but I wonder if a polygraph is useful as an intimidation tactic? Maybe you can't detect lies with any sort of accuracy but you can intimidate people into making more mistake when answering questions and that can be used to figure out if someone is lying? OR perhaps they can pressure some people into revealing more information than they otherwise would?

Yes that's how it's used. That depends on people believing polygraphs work though, which is why polygraph companies for decades have been litigating against people who question polygraphs. Sometimes just the idea that there will be a polygraph test is enough to get people to be more truthful. It's like placebo drugs - if it works somehow, should we care about whether it actually works? By that reasoning, should we allow homeopathic drugs for healthcare insurance reimbursements? If Josie doesn't have a headache after taking pills, does it matter whether those pills are paracetamol or water with a story of it being very potent water? Fun discussions, not very productive, but still fun (for a while).

"That depends on people believing polygraphs work though"

Are you sure that's true? In medicine, apparently placebos have an effect even if you know that it's a placebo. I imagine that even if you know that it's theoretically useless, being hooked up to a machine that can read your vitals while lying would still be nerve wracking.

Having an effect is different from being able to sell a product based on that effect. For regulated fields like pharmacy, the FDA regulatory approval test requires proving efficacy against a placebo. A doctor may (under certain specific circumstances) treat a patient using a placebo (because medicine's aim is to do whatever that is necessary to alleviate the problem or reduce suffering, it is different from pure biological natural sciences/pharmacy where inferences must be backed up by scientific theory and validated by empirical evidence) but it does not necessarily mean that a placebo can be sold/marketed as a cure.

To a degree of course, just 'but it might work' would be enough I guess, the same way someone needs to at least not be told something is a placebo for a double blind study to be "valid" ("methodologically sound" would a better term I think?). I did read quite a lot on the topic and much has been written about it over the years, but this was 10+ years ago for me, I don't remember enough to really make a coherent argument that addresses the details.

There was a tv show in the uk where they used them to prove/disprove infidelity - I think it caused people to actually break up.

The show (Jeremy kyle) was taken off air because someone who failed the polygraph committed suicide.

https://www.telegraph.co.uk/news/2019/05/13/jeremy-kyle-take...

On the Jeremy Kyle show, the lie detector drove one guest to suicide (which led to the show's cancellation):

https://www.telegraph.co.uk/news/2019/05/22/jeremy-kyle-gues...

I'd guess that polygraph tests need belief into them working, thus making it work. Polygraphs should be able to (at least) measure nervousness correctly (e.g. due to transpiration), so if you believe polygraphs may work you're probably someone on which they will work (1).

In other words, long proven nonsense as long as you don't believe in it.

(1) https://antipolygraph.org/lie-behind-the-lie-detector.pdf (Chapter 3)

Hypnosis comes to mind :-)

Per the article:

>It is to be noted that around the time Ma applied for employment with the FBI, the Bureau had a roughly 50% polygraph failure rate for special agent applicants, with many honest persons being wrongly branded as liars and barred for life from FBI employment

So either 50% of FBI Applicants were actually foreign agents AND believed in polygraphs (why would they if they were trained foreign agents?) OR it's just total bullshit. I think the "it works if you believe in it and some people do" myth is just that...

It's a very attractive idea that we can tell (even partially) whether someone is lying. We actually might be able to with an fMRI setup I think. But polygraphs should be long gone as rubbish. I have no idea why anyone in the USA takes them seriously.

> So either 50% of FBI Applicants were actually foreign agents AND believed in polygraphs (why would they if they were trained foreign agents?) OR it's just total bullshit. I think the "it works if you believe in it and some people do" myth is just that...

It's even dumber than that. From what I've heard, the big failure rate is often with respect to drugs. You're allowed to have experimented with marijuana a specific, small number of times.

You're wrong, they do not magically start working if you believe in them. If you're nervous for ANY reason it will give off a false positive. Not only if you're nervous of the machine itself.

It is insane it's still being used in the US.

> If you're nervous for ANY reason

Agree, and also agree, it's insane. Still that's the presumed thinking behind it.

The (anti-polygraph-myth) site I linked comes to a similar conclusion.

In former CIA officer Valery Plame's book Fair Game, she describes how an old hand at CIA told her that the best way to get through the polygraph is to be as detailed and honest as possible. Even on subjects that would be embarrassing, merely focussing on describing the truth and knowing that the interviewers appreciate candor can often alleviate nervousness.

I've never been polygraphed and I have conflicting views on it, but I suspect if I were ever in the same situation I'd do the same thing. They may not work perfectly, but they are a forcing function to the interviewee. Are you going to tell the whole truth in all its messy detail or not?

That said, I don't think they belong in the justice system. Someone who is already accused of a crime has to choose between either doing a polygraph and being potentially being nervous because their freedom is at stake, or denying the polygraph and looking guilty.

Polygraphs are not used in US courts and the results are not admissible at trial, so I'm not sure what you're referring to in the last paragraph.

I think there is confusion/conflation with defendants offering to take a polygraph to prove innocence. Sometimes it’s a naive offer sometimes it’s someone who wants to “show proof” they “didn’t do it”.

Which is part of why they're inadmissible regardless of who wants to use them.

Sure but it’s usually a PR stunt by the defense “see my client is willing (therefore innocent as no liar would take the test the CIA uses to expose moles)”

“We took a privately administered test by a certified polygraph administrator and my client passed with flying colors!!!”

If I remember correctly, note this is contrary to the advice the antipolygraph sites gives. They state anything the person interviewed admits, no matter how trivial, will be used against them (e.g. "have you ever smoked pot in college?"). That the "good cop" of the interrogation is always a ruse; and that since polygraphs don't actually work, small "admissions" are a big part of the actual information gathering... including the questions that are allegedly for "calibration".

One of Obama's staff, maybe press secretary said something similar. On NPR she said when they pressed about marijuana use in the screenings, she told them flatly she used it 500+ times.

But like you said, in a legal proceeding they are terrible to use.

No, they don't belong anywhere. They are still useless.

> You're wrong, they do not magically start working if you believe in them. If you're nervous for ANY reason it will give off a false positive. Not only if you're nervous of the machine itself.

If you're just as nervous during control questions as lies then it would be a false negative. The "tack in shoe" tactic is supposed to make yourself uncomfortable during control questions by stepping on the tack and raising the baseline.

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