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The Human Lie Detector Versus the Lie Detector Machine

“I’m telling you the truth.”

Wouldn’t it be great if you could always believe that? Unfortunately, neither a body-language expert nor a polygraph machine can determine whether that statement is truthful with 100-percent accuracy, 100 percent of the time. Nevertheless, I have more trust in the body-language expert to detect deception than I do a polygraph machine. Did you know that the polygraph machine can’t detect lies? It detects stress, so it should actually be called a stress-detector machine. Do most people show signs of stress when they lie? Absolutely! But not everyone does.

So why, then, do interrogators, police, courts of law, and intelligence agencies rely on polygraphs to find ...

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