The Early Polygraph | PEi Wiki

In 500bc, the Indians had developed one of the first ever lie detectors.

Their technique involved placing a knife into a fire until it became red hot. The accused would then be forced to open their mouth and the hot knife would be placed on their tongue.

The theory being, if the suspect was innocent and telling the truth, their tongue would be moist and would not blister when touched with the knife.

However, if the accused were lying, their mouth would become dry, the knife would stick, and the tongue would instantly blister. 
If this happened, they would be deemed guilty and their tongue would be cut off!

Brutal? Yes. Scientific? Yes.

When we experience stress, such as the stress created by lying, our nonessentials such as the digestive and immune system shut down. This occurs because our blood has been directed to the areas of the body where it is needed the most, such as the large muscles in our legs (so we can run away), and arms (our best weapon). This is known as the fight or flight response.

Can anyone spot the potential flaw with this technique?

A hint?… It’s the same flaw the modern day polygraph has.

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