The 1939 lie detector that tested the power of kisses

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"Kiss on the lips causes the maximum reaction, swings the needle to the end of the dial."

Image: Herbert Gehr/The LIFE Images Collection/Getty Images

Feb. 2, 2015 marks 80 years since a polygraph was first used to bring a conviction in a U.S. court.

NYPD criminologist Roy Post invented his own version of a lie detector machine. Called the Postometer, the test theoretically detected not only criminal suspects, but also to discovered the truth, or otherwise, of people’s reactions to emotional stimulus. 

The subjects of Post’s experiments placed their hands on a pair of metal plates. Their blood pressure and temperature generated a small electrical current, indicating an emotional change had occurred. The Postometer amplified these currents and displayed their levels on its needle and dial. Read more…

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