How do lie detectors work??

Question

Just curious

Answer 1

Hi lie deyectors monitor changes in pulse heartrate perspiration blood pressure  things like that    

Answer 2

A poly graph (aka lie detector) is like a set of different medical devices that measure physiological changes in the body. (heart rate, blood pressure, respiration, and perspiration. Basically these poly graphs don't say whether or not you are lying. It is up to the poly graph examiner to determine if fluctuations from normal heart rate, etc, are signs of deception.

The reason it's hard to "fool" a poly graph is because when you tell a lie, your body goes thru stresses and physiological changes you aren't in control of. I suppose the only to pass a poly graph is to tell the truth or to believe you own lies. The last of the two options would make you a psychopath, sociopath, or just delusional.

anyway, hope that helps.

~chai