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Comment by mherdeg | Hacker News Reader

Yeah I treat it as "common knowledge" that polygraphs work about as well as the ADE 651 (https://www.nytimes.com/2009/11/04/world/middleeast/04sensor...).

It's always fun to think about how I could be totally wrong tho. Thought experiment:

Suppose you had a piece of technology which could infallibly detect whether someone thinks they are telling the truth.

To preserve the device's maximum efficacy, would you (a) keep it a secret and only use it for ultra-high-stakes investigations (as with cell-site simulators - e.g. https://arstechnica.com/tech-policy/2015/04/fbi-would-rather... ); or (b) promulgate the idea that it is worthless or can be trivially manipulated to return any result, and train people to use it for everything?

Hard for me to distinguish between a world where the polygraph does nothing and everyone knows it; and a world where the polygraph does nothing and everyone knows it (but that's just what they want you to think)

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It's a fun idea, but even the premise points out the major fault: "whether someone thinks they are telling the truth".

Studies on memory show that human beings, as a whole, are terrible at remembering things. We edit, we re-write, we create. Almost certainly some event you remember clearly from more than 20 years ago either did not happen at all, happened to someone else and you heard about it, or happened in a completely different way than you remember. That's true for just about everyone[0].

What good is a device that can tell if you believe you're telling the truth when your beliefs and memories are so flaky anyways?

[0] Except my wife, whose near-eidetic memory is frightening.

> Studies on memory show that human beings, as a whole, are terrible at remembering things.

I always remember testifying in court about an assault that took place some months earlier. By the time I was actually there, I couldn't remember the event at all. I simply remembered describing the event previously (a bunch of times).

Did I see what I said I did? I believe so. Was the testimony in court worth anything at all when compared to the Police interview 2 hours after the fact? God no.

At that point my truth was that I was confident that I didn't lie in previous testimony. That's it. As you say - what value is there in something which tests that?

Exactly. What's worse is that society presumes that memory is faultless. If you honestly said in court that you couldn't remember very well, but that you believe your statement to be accurate (the truth), a judge and jury would both agree that you were less truthful, or trying to cover up the truth.

And even if we agree that memory is faulty, no one agrees that their memory could be faulty. Just everyone else's.

My favourite example of this is my father. He tells a story about some funny event that happened to him up at his parent's cottage when he was in his 20s. Right after it happened, he told his family, including his brother. Within a few years, his brother started telling the story like it had happened to him- and in fact seemed to believe it did happen to him. My father tells me that and scoffs, saying "See how faulty memory is? Your uncle remembers an event that never happened to him!". I asked him "How do you know it's his memory that's wrong and not yours, since memory is so faulty?" "Oh now, I know that my memory is right".

Apparently jurors generally have a wrong understanding of how memory works.[0] Sometimes I feel like it isn't really a privilege to be judged by your peers.

[0] http://www.physics.smu.edu/scalise/P3333fa14/Eyewitness/Eyew...

Penn Jillette likes to discuss this. Having worked so long with one person, they have a lot of shared stories. And he tells of listening to Teller tell a story and know that he's full of shit, getting nearly everything wrong. And also having Teller listen to him tell the same story, and thinking he's full of shit and getting everything wrong.

And then there's the third person or some sort of record of the event that shows that both of them are full of shit and getting everything wrong.

And it's especially scary knowing that memories can be suggested to people, to the point that they genuinely believe they experienced the false memories.

They can’t subvert everybody. In the latter world, you’d have some independent researchers saying it was highly accurate. In reality, the ineffectiveness of lie detectors doesn’t seem to be in any dispute when studied scientifically.

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