Tickling

Humor and Tickle

One of the most mysterious aspects of tickling is that a physical stimulus can produce a response that looks so much like that which occurs during amusement and humor. The fact that smiling and laughter appear during both tickling and humor has led many to assume that the two reflect the same positive emotional state. Charles Darwin (1872/1965), the father of evolution, was one of the most notable advocates of this view. He thought that tickling was essentially a physical joke. In arguing for this, Darwin suggested that both humor and tickling require similar preconditions in order for laughter to emerge, including an element of surprise, a pleasurable mental state, and a “light” elicitor (a light touch for tickling and a nonserious topic for humor).

While this view has intuitive appeal, several research findings suggest that tickle and humor are not simply two forms of the same internal state. For one, with humor there is a warm-up effect such that jokes that occur later in a series are found to be funnier than those that occur earlier in the series. However, listening to jokes does not make people laugh and smile more in response to tickling, and being tickled right before listening to jokes does not make the jokes seem funnier. Thus, there does not seem to be a warm-up effect that transfers from humor to tickling or vice versa, as would be expected if the two states were really tapping into the same internal experience.

Detailed analyses of facial expression also suggest differences between tickle and humor. The smile that accompanies positive emotional states such as humor usually includes two facial actions: the upturning of the lips (contraction of the zygomatic major), and a crinkling around the eyes (contraction of the orbicularis occuli), called a Duchenne smile. This type of smiling occurs less frequently during tickling than during comedy, and when it [Page 766]does occur seems different. For example, in one study, some people displayed Duchenne smiles even when they were not feeling positive emotions (i.e., did not report being particularly happy or amused). Duchenne smiles also were correlated with finding the tickle sensation unpleasant for some people. Furthermore, when tickled, people who report generally not enjoying being tickled smiled just as much as people who reported generally enjoying it. The dissociation between smiling and self-reported positive affect during tickling provides some support for the hypothesis that tickle-induced laughter and smiling are not dependent on positive affect. This suggests that these expressions need not reflect merriment and mirth any more than crying when cutting onions need reflect sorrow and sadness.

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