This is misunderstood. The Polygraph is not scientific, and can't reliably detect dishonesty. However, lots of people will admit to things under interrogation and bullying. What the polygraph is actually doing for the interrogators is simply to provide a formal way to read body language. And of course, to provide what is effectively a robot-bad cop. "Gee, I dunno, the test says you're lying. Are you sure there's not anything you want to tell me?"

It doesn't work for objectively detecting dishonesty. That part is myth and theater. However, it does work as a way of directing an interrogation so as to maximize anxiety (since anxiety is more or less what the polygraph actually measures).

From what I've read about it, it works to some extent as long as people believe in it. They want to get their clearance and believe cheating could be detected, so they tend to be more truthful. It's based on intimidation and observation. The examination starts when you enter the building and stops when you leave it.

> If they know polygraph doesn't work, why do they still do it?

The airport is not the only security theater the Americans operate :)

The real reason: it's an excellent pretext to interrogate your employees with a prop to convince them to spill any beans they might be holding.

Because belief is not rational. The people that passed the polygraph tests and administer them to others may acknowledge the flaws but they still 'know' that a lie detector is the best they have got. They also know that some people will just confess at the thought of being wired up to such a machine, to give evidence that, unlike the lie detector, is admissible in court.

The most interesting story is how the authorities nabbed the guy who was most dedicated to dismissing the lie-detector baloney:

https://www.theguardian.com/us-news/2015/may/12/polygraph-cr...

His consulting work of helping people pass lie detectors was his downfall. Had he just stuck to campaigning against the lie detector and not wanting to offer services to those needing to pass a lie detector test then all would have been okay for him and he would not be having to serve one of those silly 100 year sentences that American justice demands.

Why Facts Don’t Change Our Minds: https://news.ycombinator.com/item?id=18099488

It does somewhat work in the same way that homeopathy somewhat works. The placebo effect of convincing people that it works produces some results on naive people.

Not to mention that eliminating the polygraph would require someone to admit that they were wrong about using a polygraph.