by Blaine Greteman

Laughter predates the development of language. Almost all mammals do it, and it’s one of the first things babies learn. “One of the unique characteristics of mammals is that we play,” advises Dacher Keltner, a psychology professor at the University of California, Berkeley, and author of Born to Be Good: The Science of a Meaningful Life. Nearly all social mammals tickle one another, and emit pleased, laugh-like pants, chirps or grunts when tumbling about in playful situations. He explains that, “As you get more complicated in the mammalian structure, you have a greater vocabulary of play, including laughter.”

When apes play, they roughhouse, tickle and laugh. Chimpanzees pant with delight in response to pratfalls. Robert Provine, a neuroscientist at the University of Maryland, in Baltimore, who is studying laughter for insights into the biology of social behavior, maintains that laughter is a kind of evolutionary link between all mammals. He remarks, “If you tickle a rat, it laughs; we just can’t hear it.” (Listen in at OdeMagazine.com/laughingrats.) On the other hand, no matter how much you tickle a lizard, it won’t guffaw, chuckle or purr.

Among Provine’s more startling findings is the fact that only 10 to 15 percent of laughter follows a humorous statement or situation. Most laughs follow utterly banal comments, like, “See you later” or “I think I’m done.” As Provine and others observe, “The essential ingredient for laughter is not a joke, but another person,” making laughter primarily a social lubricant.

Laughter is 30 times more likely to occur in group situations than on solitary occasions, and Provine’s research reveals tantalizing insights into the way it structures our daily interactions: Speakers laugh more than listeners; women laugh more than men; laughter punctuates our phrases, but doesn’t interrupt them; and laughter is contagious. During an episode of laughter, we can signal appreciation and understanding of others. Perhaps more importantly, says Provine, we share a mental and acoustic space.

“Laughter puts us into side-by-side existence in this playful realm,” says Keltner. “It signals a shared understanding of the world, so it’s foundational to interdependence and intimacy and like-mindedness.” In short, laughter is the glue that holds people together, a bridge between our self and others.

“Our relationships,” concludes Keltner, “are only as good as our histories of laughter together.”

Blaine Greteman is a freelance writer and professor of English at the University of Iowa. Connect at [email protected].