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Arm stretching illusion

Manipulating sounds can trick your brain into thinking your limbs are longer than they are

A person taps a point (•) 10 times with their right hand in time with a flashing LED, and a hidden speaker amplifies the sound. Without leaving their seat, they repeat the taps at each point

Hidden speaker location matches tap location

In the next trial, the speakers are placed at double the distance between the person and each tapping point. Before and after each trial participants were touched in two places simultaneously on their right arm and on their left

Double distance

When the tapping sounds originated f rom double the distance, participants perceived the touches on their right arm to be significantly f urther apart than they really were

Their brain perceived the right arm to be longer Quadruple distance

When the speakers were f urther away the illusion wasbroken