A Lie Detector For The Power Of Kiss, 1939

New York Police Department Criminologist Roy Post invented his own version of a lie detector machine called the Postometer, the test theoretically detected detected not only criminal suspects, but also revealed the truth, or otherwise, of people's reaction to emotional stimulus.

"Kiss on the forehead creates little emotion, as shown by small movement of needle." (IMAGE: HERBERT GEHR/GETTY IMAGES)

The subject of Roy's experiment placed their hands on a pair of metal plates. Their temperature and blood pressure generated a small electrical current, indicating an emotional change that had occurred. The Postometer amplified these currents and displayed their levels on its dail.

"Needle at 50 picked 'the witness' in our experiment and (below) at 150, picked 'the thief."(IMAGE: HERBERT GEHR)

While the technology has improved a lot, polygraph test results by scientific and government bodies generally suggest that polygraphs are highly inaccurate, and are unreliable means of assessing truthfulness. The American psychological Association stated " Most psychologist agree that there is little evidence that polygraph tests can accurately detect lies. "

"This man looked guilty, but the detector proved he was innocent." (IMAGE: HERBERT GEHR/GETTY IMAGES)

The most meaningless thing in the world is the act of two women kissing. That does not even make the needle quiver.

- ROY POST, 1939

IMAGE: HERBERT GEHR/THE LIFE IMAGES COLLECTION/GETTY IMAGES

"Kiss on the lips causes the maximum reaction, swings the needle to the end of the dial." (IMAGE: HERBERT GEHR/GETTY IMAGES)