How does the lie detector test work?

[Blacksnake285]

How does it determine if somebody lied?

[Astarlessnightsky]

Measures heart rate, sweat intensity, blood pressure and many other bodily functions.

In case you tell a lie the small change in these bodily functions would show up.

At least thats the theory, it isn't 100% accurate and isn't used besides movies anymore.

[Billlewis]

I had to take one once, and they're virtually impossible to beat. They attach a lot of clips and wires to your fingers and then ask you questions. Whenever you answer a question untruthfully, the indicators will show that on the page. Although they're still inadmissible in court, they are often used to screen potential job seekers.

[exitseven]

It can register changes in a persons metabolic processes. Heart Rate, skin temp. , respiration and other measurable responses. The theory is that people's metabolisms change under stress and for most, lying puts the body under stress.