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Pleasure or pain? Social response or reflex? Tickling and the laughter it induces are an enigmatic aspect of our primate heritage
Why do we laugh when we are tickled? Perhaps we enjoy being tickled or find it funny. But if so, why do most people, especially adults, say they hate to be tickled? And why do I not laugh when I try to tickle myself? If the answer to the peculiar riddles of tickling (or, to use the term preferred by some writers, tickle) were simple, the topic might not have engaged many of the great minds of the past. In fact, illustrious thinkers have pondered tickle's mysteries for over two millennia. Plato, Bacon, Galileo and Darwin ventured opinions about the nature of tickle and ticklish laughter. Among the ancients, Socrates suggested that the tickle sensation is to some degree pleasant-but to a greater degree painful. Aristotle raised the question of why one cannot tickle oneself:
Is it because one also feels tickling by another person less if one knows beforehand that it is going to take place, and more if one does not foresee it? A man will therefore feel tickling least when he is causing it and knows that he is doing so. Now laughter is a kind of derangement and deception ... that which comes unawares tends to deceive, and it is this also which causes the laughter, whereas one does not make oneself laugh.
Francis Bacon (1677) and Charles Darwin (1872) agreed that humorous laughter requires a "light" frame of mind. But they differed on ticklish laughter: Darwin thought that the same light state of mind was required, whereas Bacon said no: When tickled, noted Bacon, "men even in a grieved state of mind, yet cannot sometimes forbear laughing."
Scientists of this century have seemed less intrigued by the questions of tickle, but recently the topic has lent itself to empirical study that is beginning to produce clues to this enigmatic feature of human behavior. Although I rather dislike tickling, I have found it a challenging research topic. Here I would like to share some of the clues and curious possibilities emerging from my own work and that of others.
What Is Tickle, Anyway?
There are two phenomena that we...