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Why We Laugh

Laughter is more complicated -- and bizarre -- than you might think.

Laughing Is Contagious

The cynical answer is that sitcoms are so witless and unfunny that we need to be told where the jokes are. But this misses the point. Why does hearing other people laugh make us more likely to laugh ourselves?

Everyone's experienced this on a small scale. Seeing someone in hysterics -- even if you don't know who the person is or why she's laughing -- can set you laughing too. Why?

The answer lies in the evolutionary function of laughter. Laughter is social; it's not a solo activity, says Provine.

"We laugh 30 times as much when we're with other people than we do when we're alone," says Provine.

You might assume that the 'purpose' of a laugh is to express yourself -- to let people know that you think something is funny. But according to a 2005 article published in the Quarterly Review of Biology, the primary function of laughter may not be self-expression. Instead, the purpose of a laugh could be to trigger positive feelings in other people. When you laugh, the people around you might start laughing in response. Soon, the whole group is cheerful and relaxed. Laughter can ease tension and foster a sense of group unity. This could have been particularly important for small groups of early humans.

In some cases, laughter can in fact become literally contagious. History is dotted with accounts of laughter epidemics. In 1962, in the African country that is now Tanzania, three school girls began to laugh uncontrollably. Within a few months, about 2/3 of the school's students had the symptoms, and the school closed. The contagion spread, and eventually affected about a thousand people in Tanzania and neighboring Uganda. There were no long-lasting effects, but it shows how responsive people can be to seeing another person laugh.

So sitcoms -- or anything else -- seem funnier to us when we hear other people laughing at them. We've evolved to be that way.

Why Do Villains Laugh Diabolically?

Clearly, there are many different types of laughter. The explosion of laughter after being tickled is obviously different from the tight-lipped chuckle you force out of yourself when your boss tells a bad joke.

To account for the differences, some researchers divide laughter into two groups. The first includes spontaneous laughter. The other group includes laughter that is less spontaneous: it includes fake laughter, nervous laughter, and other social laughter that is unconnected to humor.

Some argue that this nonspontaneous laughter might also include a diabolical cackle or the cruel, jeering laughter that we once heard on the playground.

"Laughter does have a dark side," says Provine. "When gangs or groups of militants attack someone, they are often reported to laugh while doing it." It's the sinister aspect of laughter's power to form group cohesion. Sometimes, those bonds can be used to exclude or persecute others.

According to some researchers, these two types of laughter -- spontaneous and nonspontaneous -- actually have different origins in the brain. The spontaneous laughter originates in part from the brainstem, an ancient part of the brain. So it might be a more original form of laughter. The other type of laughter comes from parts of the brain that developed more recently, in evolutionary terms.

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