Question 1

Why don't polygraph lie detectors work?

Accepted Answer

Polygraphs measure physiological arousal such as heart rate, blood pressure, and sweating, not lying itself. An innocent but frightened person can look guilty, while a calm liar can pass, so the results are close to unreliable. The National Academy of Sciences found the science behind them scientifically weak.

Question 2

Can body language really reveal if someone is lying?

Accepted Answer

Some cues, like microexpressions and a rising vocal pitch, do leak genuine emotion, but no single body-language signal reliably indicates a lie. Even trained experts detect deception at only about 54 percent accuracy, barely better than chance.

Question 3

What is the most reliable way to detect a lie?

Accepted Answer

The most reliable approach is verbal, not physiological. Skilled interviewers look for inconsistency in a person's story by increasing cognitive load, asking for events in reverse order or unexpected detail, and watching whether the account holds together under gentle pressure.

forensics

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