Tickle torture is the use of tickling to abuse, dominate, humiliate or even "prank" someone. The victim laughs even if he or she finds the experience unpleasant because the laughter is an innate reflex rather than social conditioning. Tickle torture can either be consensual or forced, depending on the circumstances. If tickle torture is consensual, it is usually done as a part of some sort of sexual ritual or another mode of affection. Forced tickle torture can either be used for mild interrogation purposes or simply for a harmless method of dominating someone.
Tickle torture has become the subject of many fetish/sexual publications. These fictional writings can portray a fantasy of a desirable character, often a celebrity, being restrained and interrogated. These stories are not always sexual, although they are mostly the object of sexual fantasies and dreams. Because of the fantasy element of the plot, the characters are often magical or the circumstances are completely imaginative.
Knismesis and gargalesis are the scientific terms, coined in 1897 by psychologists G. Stanley Hall and Arthur Allin, used to describe the two types of tickling. Knismesis refers to the light, feather-like type of tickling. This type of tickling generally does not induce laughter and is often accompanied by an itching sensation. Gargalesis refers to harder, laughter-inducing tickling, and involves the repeated application of high pressure to sensitive areas. This "heavy tickle" is often associated with play and laughter.
The knismesis phenomenon requires low levels of stimulation to sensitive parts of the body, and can be triggered by a light touch or by a light electrical current. Knismesis can also be triggered by crawling insects or parasites, prompting scratching or rubbing at the ticklish spot, thereby removing the pest. It is possible that this function explains why knismesis produces a similar response in many different kinds of animals. In a famous example, described in Peter Benchley's Shark!, it is possible to tickle the area just under the snout of a great white shark, putting it into a near-hypnotic trance.