Postometer: A Lie Detector Machine That Measures the Emotional Reaction of Kisses in 1939

In 1939, New York City Police Department used a lie detector machine to test the emotional reaction of kisses. The machine, called the Postometer, was invented by criminologist Roy Post with his own version. 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.

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

Needle at 50 picked 'the witness' in our experiment and (below) at 150, picked 'the thief.

Needle hardly moves because this man did not steal the briefcase in our experiment.

This man looked guilty, but the detector proved he was innocent.

Kiss on the forehead creates little emotion, as shown by small movement of needle.

(Photos: Herbert Gehr/The LIFE Images Collection/Getty Images, via Mashable/ Retronaut)