What causes people to laugh when tickled?
Laughter as a reaction to tickling remains one of science’s great mysteries, despite the musings and research of legendary academics such as Aristotle, Plato and Darwin. Theories abound, from its functions as an evolutionary response to protect oneself to a form of physical bonding between individuals in familial or intimate relationships. What scientists do know is that the ticklish feeling is a result of two factors: the physical stimulation of nerve fibers linked to both pain and touch, and the mental reaction of nervousness. On the physical side, tickling can occur in two ways. The feeling that results from a light touch, such as that of a bug crawling on your skin, is called knismesis. Laughter-inducing tickling, or gargalesis, occurs as a response to heavier contact, with the most ticklish areas often being under the chin or arms, the torso and the soles of people’s feet. Mentally, the touch activates a nervous response of both surprise and discomfort, though facial expressions a
