Interpolation of Illusory Pain in the Human Somatosensory System

Three coins are lined up with the middle coin at room temperature and flanking coins cooled down to 4° C. If digits 2 and 4 are placed on the outer coins and digit 3 on the middle coin, the latter also feels cold; a striking example of perceptual filling in of temperature. We show that if digits 2 and 4 are placed on a thermal grill with alternating hot and cold bars, while digit 3 is placed on cardboard, the sensation of pain will also spread to the middle finger.