WASHINGTON - So a scientist walks into a shopping mall to watch people laugh.
There's no punchline. Laughter is a serious scientific subject, one that researchers are still trying to figure out.
Laughing is primal, our first way of communicating.
Apes laugh. So do dogs and rats. Babies laugh long before they speak. No one teaches you how to laugh. You just do. And often you laugh involuntarily.
You may laugh at an April Fools' prank. But surprisingly, only 10 to 15 percent of laughter is the result of someone making a joke, said Baltimore neuroscientist Robert Provine. Laughter is mostly about social responses.
"Laughter above all else is a social thing," Provine said. "The requirement for laughter is another person."
"All language groups laugh 'ha-ha-ha' basically the same way," he said. "Whether you speak Mandarin, French or English . . . There's a pattern generator in our brain that produces this sound."
Deaf people laugh without hearing, and people on cell phones laugh without seeing, points out Provine, author of the book "Laughter: A Scientific Investigation."
Chimps tickle each other and even laugh when another chimp pretends to tickle them. "That's my candidate for the most ancient joke," Provine said. "It's a feigned tickle. That's primal humor."
Northwestern University biomedical engineering professor Jeffrey Burgdorf has found that laughter in rats produces an insulin-like growth factor chemical that acts as an antidepressant and anxiety-reducer. He thinks the same thing probably happens in humans, too. - AP