Why do people laugh when tickled? Why can’t you tickle yourself? Why are certain parts of the body more ticklish than others? Why do some people enjoy tickling and others not? And what is tickling, after all? In fact, it is not so easy to pin down the phenomenon, as a number of scientific studies attest. Here’s one attempt at a precise description: “Tickle may thus be finally defined as an intensely vivid complex of unsteady, ill-localized and ill-analyzed sensation, with attention distributed over the immediate sensory contents and the concomitant sensations reflexly evoked.”3 Coming at the end of some fifty pages of scientific investigation, such a vague and “ill-analyzed” conclusion might well disappoint. But perhaps there is a lesson to be learned here: any definition of tickle must be able to account for its lack of definition, its equivocal and evasive dynamism. Another researcher, Thomas Mintz, tried to render tickle’s shifting character by highlighting precisely this wandering mobility: “tickle—the itch that moves.”4 As Mintz argues, tickle, itch, and pain are very closely related on a neurological level, yet are interpreted by the brain as distinct phenomenological states: whereas an itch is experienced as a well-localized sensation that is “on” the skin and may be reached by scratching, a tickle consists in a shifting stream of stimuli that is “outside” us, and against which we push in convulsions and spasms. Pain, on the other hand, is “inside” and thus cannot be escaped.5 In an article now considered a classic in tickle studies, psychologists G. Stanley Hall and Arthur Allin distinguish two types of tickling: the first, which they name knismesis, is caused by a light movement across the skin, the feather-type of tickle, while the second, gargalesis, is provoked by the stronger pressure of poking and other movements. If the latter is more commonly associated with play and laughter, the former contains tickling’s true mystery:

Why is it that contact with the finest hair, wool, or cobweb evokes sensations that are not only exceedingly intense, but also very widely irradiated, and also provokes reflex movements that may be convulsive in their intensity, but when the same pressure, it may be of the same object and upon the same spot, is slightly increased, only the localized and moderate impression of touch is produced, with proper or no motor reactions?6

Does not tickling violate the basic mechanism of cause and effect, the principle that every action entails an equal and opposite reaction? The tiniest stroking produces a wildly explosive response, while a more vigorous rubbing may hardly elicit any reaction at all. On the most stupid bodily level, there is something miraculous in the activity of tickling that seems to contravene the everyday experience of causality, turning us into spontaneous philosophical skeptics. It is as if the lived body were split into two: a practical body governed by regular principles and interactions, and an oversensitive flesh that, with the slightest tingle, is apt to plunge all coordination and mastery into spasmodic helplessness.7

THE OLDEST JOKE

While scientific research has refuted Aristotle’s claim that tickling is a uniquely human privilege—not only has tickling been observed in our primate cousins, but scientists have recorded laughter-like ultrasonic chirping in tickled rats—it has confirmed his intuition regarding the importance of this seemingly marginal and unserious phenomenon.(An additional note on animal tickling: the most famously ticklish beast is no doubt the trout, which falls into a trance-like state when its underbelly is lightly rubbed. This has been known for ages; in Shakespeare’s Twelfth Night, Maria says, while planning to trick Malvolio, “Lie thou there; for here comes the trout that must be caught with tickling.”) Far from being a meaningless spasm, tickling is intimately bound up with human development and the sense of self. Such is the argument expounded by neuroscientist Robert Provine, who sees in tickling an important form of preverbal communication and an element in the creation of the distinction between self and other. A primal, neurologically programmed mode of interaction, tickling creates intimacy through a benign and playful aggression. And the well-known inability to tickle oneself serves an important role in educating the infant about the limits of its own bodily experience, poignantly signaling the difference between self-affection and being affected by the other.

Let us focus on one detail of Provine’s theory, a rather extravagant speculation. Linking tickling not only with humorous laughter but also with the prehistoric birth of comedy, Provine writes: “I forge recklessly into the paleohumorology fray, proposing my candidate for the most ancient joke—the feigned tickle. (Real tickling is disqualified because of its reflexive nature.) The ‘I’m going to get you’ game of the threatened tickle is practiced by human beings worldwide and is the only joke that can be told equally well to a baby human and a chimpanzee. Both babies and chimps ‘get’ this joke and laugh exuberantly.”9 Here we should underline the subtlety of Provine’s argument: ticklish laughter is not yet properly comic because it is too much of an automatic or neurological reaction. The joke first enters the scene with a distancing from reflex, when the tickling play is itself played with and made into a spectacle, when the suspended, not the real, gesture gets a laugh. The Ur-joke, the zero-degree of comedy, the pretend tickle may also be seen as a primordial manifestation of culture as a virtual space detached from immediate reflex and natural instinct.