APES DO IT | June 28th 2008

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The study of laughter has entered mainstream psychology. Anthony Gottlieb reads the reports--and a new book on the history of jokes--and finds much to chuckle over ...

This spring, several newspapers published a suspiciously amusing story. Recent studies of twins, they reported, suggested that there may be a genetic explanation for some differences between British and American styles of humour. In particular, a penchant for aggressive sarcasm and self-deprecation may lie in British genes. And pigs may fly--but I'm just a Brit, so what would I know about it?

Joking apart, the studies provide only the flimsiest support for a genetic theory of national humour: as with plenty of headline-grabbing science reports, the data falls rather short of the headlines. The real news is that the investigation of humour is belatedly becoming a science. After millennia of untested speculation by armchair thinkers, moves are afoot to bring the study of laughter into the mainstream of experimental psychology. As Rod Martin, a professor at the University of Western Ontario, notes in his textbook "The Psychology of Humor", which was published last year, humour is found in all human cultures and is ubiquitous in everyday life. His own studies suggest that on average people laugh 17.5 times per day. And a good sense of humour tends to be one of the most highly rated traits when people choose their friends, lovers or spouses. So psychologists have every reason to take humour seriously.

Perhaps "seriously" is not quite the word, though. Of the dozens of experiments discussed in Martin's textbook, few manage to avoid a hint of the absurd. Blindfolded subjects are tickled by experimenters who they are told are machines. The sexual banter in an all-night diner in upstate New York is surreptitiously observed. People study cartoons with pens stuck in their mouths (to contract the facial muscles associated with smiling). An experimenter "accidentally" spills hot tea on herself when a jack-in-the-box erupts nearby. One Boston psychologist, the co-author of a paper entitled "A Threshold Theory of the Humor Response", published in The Behavior Analyst last spring, understandably felt obliged to state in a footnote that her surname really is "Joker".

One conclusion from the new empirical approach to humour is that previous theories did not pay enough attention to play. In 1923 a theoretical tome listed 88 different theories of humour, few of which seemed to acknowledge that it is supposed to be enjoyable. The theories can be divided into three main types.

The oldest sort are "superiority" theories, whose advocates included Thomas Hobbes, Plato and Aristotle. According to this view, we laugh from sudden feelings of superiority over other people. "Relief" theories are best known from the work of Freud, though the first such account was proposed by Herbert Spencer (who was an editor at The Economist). On this type of theory, laughter releases pent-up psychic energy. The third sort of theory focuses on the incongruity which is allegedly found in all humour. This idea has been traced back to the 1750s and was endorsed by the philosophers Kant and Kierkegaard and the novelist Arthur Koestler. Nowadays, researchers tend to see humour as part of our mammalian inheritance, and as closely related to rough-and-tumble social play.

Like children, apes laugh during chasing, wrestling and tickling games. Chimps and gorillas who have learned sign-language have used it for punning, incongruous word use and playful insults. Intriguingly, it seems that rats may laugh too. A team of researchers at Bowling Green State University reported in 2000 that rats produce an ultrasonic chirping during play and when tickled by humans. These chirps appear to be contagious, and young rats prefer older rats who produce more of them.

Rats and humans had a common ancestor about 75m years ago, and humour has clearly come a long way since then. Nobody has caught rats, or even chimps, trying to tell a joke. But another finding from recent research is that pre-packaged jokes are a less important part of humour than people may think. Jokes have a long and fascinating history--which is engagingly told in a short book, "Stop Me If You've Heard This: A History and Philosophy of Jokes", by Jim Holt, to be published in America in July and in Britain in October. But it seems that only about 11% of daily laughter is actually occasioned by jokes. Another 17% is prompted by media and the remaining 72% arises spontaneously in social interaction.

One popular field of research is the effect of humour on health, which is widely assumed to be positive. The results so far are inconclusive, and slightly disturbing for anyone who likes to laugh. Rod Martin points out that if humour is good for health, then it should be associated with longevity. Yet it appears that cheerful people live less long than their gloomier peers, perhaps because they are too jolly to worry about their aches and pains. It may be true, as the proverb says, that he who laughs last laughs longest. But it seems that he who laughs longest does not last.

(Anthony Gottlieb is a former executive editor of The Economist. Author of "The Dream of Reason", he is working on a book about nothingness. His last piece for Intelligent Life was about exonerating Epicurus, a smart hedonist who has earned too much bad press.)