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Comment by caminante | Hacker News Reader

> This is easily ascribed to the fact that the liar is either making the story up as they go or are repeating a rehearsed lie. A truthful person can jump around easily because they are recounting distinct memories.

Alternatively, the liar's experienced, good at his craft, and more capable of jumping around.

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The best liars use the exhonerative voice to avoid telling a story about themselves at all:

"Bags are subject to search" means "We will search your bags". "A shooting involving Tacoma County Police left two suspects dead" means "Tacoma County Police shot two suspects."

Huh? I'm not disputing that institutions carefully use the passive voice to clean their prose of negative connotations...but the two examples you mention are not "lies"

1. I've seen the "bags are subject to search" phrase many times, including the public library. I cannot remember the last time my bag was searched, even at the airport when the search is differentiated from the usual scan. So that phrase is definitely not a cover-up for "We will"

2. Again, not a lie. And I don't mean in the "not technically a lie". There are many cases where there is a shootout involving police and the cause of the suspect's death is ultimately determined as suicide. So the "A shooting involving..." phrase is perfectly acceptable in a breaking news update when no determination has yet been made.

> I'm not disputing that institutions carefully use the passive voice to clean their prose of negative connotations...but the two examples you mention are not "lies"

Clippy says: "Hey, it looks like you're trying to start a semantic argument! Can I help with that?"

> I've seen the "bags are subject to search" phrase many times, including the public library. I cannot remember the last time my bag was searched, even at the airport when the search is differentiated from the usual scan. So that phrase is definitely not a cover-up for "We will"

Congratulations on being middle class and white.

> There are many cases where there is a shootout involving police and the cause of the suspect's death is ultimately determined as suicide. So the "A shooting involving..." phrase is perfectly acceptable in a breaking news update when no determination has yet been made.

There are many cases where this isn't the case, too.

Actually, I'm Asian, FWIW.

By using the exonerative voice, a liar avoids committing to a particular narrative. They can easily back away from a statement by saying "I only said baggage is subject to being searched. I didn't say they were searched."

That said, I don't think the exonerated voice is a particularly skillful one. A careful listener can easily pick up on that.

Principle of Charity, my friend. I'm not really sure where you got a negative vibe from his comment. It was more of a comment on how effective word-choice is on someone's symamantic tree.

But those aren't lies, just a mixture of omission and clever wording to reframe the facts. They're used in unidirectional communication (a sign at the airport, a television broadcast), but don't hold up well when there are follow-up questions.

Only if they are aware of this technique and purposefully and skillfully prepare to defeat it. That turns out to be harder than you'd expect for methods like this. The methods used by Israeli security agents to profile travelers at airports have been well known for decades, but even so are still very effective.

How do you measure it it has been effective when the successful liar passes the test and is not defined as such?

If you catch X people trying to blow up a plane and no planes get blown up, that's fairly good evidence that your method of catching people trying to blow up planes has been 100% successful. So far.

This is one hell of a post hoc ergo propter hoc, I'll give you that at least

What's wrong with it? He's not making the usual "tiger-proof rock" argument used to refer to the TSA, after all. The TSA doesn't, as a rule, catch people who were actually planning to cause trouble. They either catch people who didn't know/care how much toothpaste they were allowed to smuggle onboard, or they catch idiots who forgot they were carrying a .50 caliber Desert Eagle in their shaving kit. This is a different argument altogether.

That is an extraordinarily dangerous notion.

Or maybe the people trying to blow up planes are just as bad at blowing up planes as you are at catching them.

Want to buy an elephant whistle?

The difference is that there are many groups who have publicly declared their intent to blow up Israeli airliners, so it's not as if you're defending against a non-existent threat.

No, but if my security guards keep turning away actual elephants at the border and I find no actual elephants nearby then I can conclude that my anti-elephant security works.

Do you know that you have a banana in your ear?

You raise an interesting conundrum, but you can tell of a certain success rate by the number of liars who eventually confess to lying or are found to have been lying.

Wouldn't that be just the same case as with the caught liars but extended to a group of people who despite being successful at the interview failed fulfilling the task? There is still an unknown group of "liars" who passed the test and never confessed.

They could be lying about whether they were lying in the past.

We're talking about legal contexts here. Almost no one, unless coerced/brutalized by police/DAs, admits to crimes they did not commit. And the you have the thing where you can verify their admission of guilt with corroborating details.

There have many many many cases of individuals getting behind bars because they have been coerced to plead guilty and confess to crimes that they never committed.

"unless coerced/brutalized by police/DAs" is not really exceptional, once in a decade, type case, sadly it is rather routine.

I know personally a person who plea-bargained, which means admitting to a crime they didn't commit, because the likelihood of being convicted (and the penalty of conviction) was so great a threat. He pled to a lesser crime (that he also didn't commit) and served 5 years.

Sadly, there is a systematic problem in which many must plead guilty because they will be punished beyond measure if they do not. It is structural and endemic in American justice:

http://www.nybooks.com/articles/archives/2014/nov/20/why-inn...

(EDIT: And this one) http://www.nytimes.com/2015/08/16/magazine/the-bail-trap.htm...

General level of terror in Israel? It is absurdly low compared to the threats that surround them (lets not go into if such threats are warranted or not)

Anybody just a little bit "smart" and lying knows that one has to be subtle and non linear. Trying to convince is already failing.

Certainly. It's not a perfect or fool proof method. Nothing is. It's simply a piece of evidence to look for.

For sure. I assume the detection technique works pretty well, even against "better" liars. That said, I've encountered folks that are so good at being slippery that you almost have to admire their skill.

That's the problem with this technique. The false positive rate is likely pretty high, and without knowing the prior probability that the person is lying, the technique could be worse than useless.

You would never convict someone of deceit based on any liar-detection methodology. They're simply tools used to warrant further investigation.

There will be truth-tellers who fail this test, but you find nothing conviction worthy. They'll be fine.

There will be liars who pass this test. Hopefully you catch them later by other means, just as you would have otherwise.

And of course, there will be those who pass who are never caught. This tool does not make that any worse.

>This tool does not make that any worse.

If the false positive rate is too high and the prior probability a given person being interviewed actually lied, then the test is actively harmful.

I.e., if a positive result is more likely a false positive, then you end up wasting investigation resources. In this case you'd have been better off just flipping a coin to decide if someone warranted more investigation.

>There will be truth-tellers who fail this test, but you find nothing conviction worthy. They'll be fine.

Tell that to all the people who lost jobs, or spent months of their life under investigation because of failed polygraph tests.

I actually failed my poly - several times :)

I should of course mention that not everyone uses these tools correctly. I suppose that could be harmful. But then again, if an investigator is simply looking for a reason to find someone guilty, then the accused is eff'ed either way.

Or the person is telling the truth and still deliberated about how to tell the story. I would probably do that.

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