Cover Story

Dishing up tacos and burritos to hungry college students may not sound like much fun, but the women behind the counter at Salsa Rico look like they're having a pretty good time. Their heads are thrown back in laughter as they yell out to each other from either end of the steam tables. Meanwhile, a student grabbing a quick solo meal stands straight-faced near the cash register.

Psychology professor Robert Provine, PhD, nods in the direction of the Salsa Rico trio as he takes in the student commons scene. The University of Maryland, Baltimore County (UMBC) psychology professor has spent close to two decades taking careful notes on situations just like this, trying to understand how and why people laugh.

Provine approaches laughter the way an ethologist might study birdsongs or Jane Goodall studied chimpanzees--by taking a step back. He tries to observe laughter as, he says, an alien who just landed on earth might: What is the strange barking or panting sound these creatures are always making, and why would such an odd behavior have evolved?

To answer those questions, Provine taped bursts of laughter and brought the recordings to a sound analysis lab at the National Zoo in Washington, D.C.--a lab, in fact, that researchers do use to analyze birdsong. He later built his own sound analysis lab to map out laughter's pitch and frequency. He has also gone into the field--shopping malls, food courts and student centers--to record notebooks full of thousands of instances of laughter, and the witty or banal conversations that provoke it.

At the moment, the staff and customer at Salsa Rico are illustrating one of his most basic findings: In general, he's found, laughter isn't inspired by particularly funny remarks. Instead, it's a ubiquitous response to social situations. People laugh when they're interacting with other people regardless of the "jokiness" of the conversation, but they don't laugh when they're alone.

"Laughter and humor are related but different things," Provine says. "Laughter is ancient. It's a primate play vocalization. Humor is a more modern, cognitive and linguistic development. There was laughter long before there was humor."

Laughter lessons

In fact, scientists from the time of Darwin have noticed that chimpanzees and other primates make a panting sound when they're tickled or playfully roughhousing. This protolaughter sounds entirely different from human laughter. Provine says it sounds more like a handsaw than a chuckle. But, he says, it's the source from which human laughter evolved.

Provine, a developmental neuroscientist by training, originally was interested in how laughter could illuminate the neurobiology of behavior. Laughter, he says, is universal among humans and has a simple structure, and so is a good system for beginning to explore the connections between the brain and behavior. But before he could begin to probe the neuropsychology of laughter, he realized, he'd have to find out more about the phenomenon itself.

At the time, in the late 1980s, the field was unexplored territory. Some psychologists had done work on the cognitive and social psychology of humor, but almost none had looked at laughter.

"Psychology generally suffers from premature hypothesis testing," he says. "The key is that you have to find the hypotheses worth testing."

To do so, he began his observational studies. Several thousand examples of laughter later, he had discovered a few unexpected facts, which he summarized in a 2004 article in Current Directions in Psychological Science (Vol. 13, No. 6, pages 215-218):

  • Laughter was 30 times more frequent in social situations than solitary ones. When alone, people were much more likely to talk to themselves or smile than to laugh.

  • We often think of laughter as a response to someone else speaking. But in conversation, speakers are 46 percent more likely to laugh than their audiences are, punctuating their own talk with laughter.

  • Only 10 to 15 percent of prelaugh comments are even remotely funny. Often, they're as dull as "I've got to go now."

  • People use laughter as punctuation, inserting it into specific places in the vocal stream. You might say "I'm going now, hahaha," but not "I'm going, hahaha, now." In fact, in a recent, not-yet-published study, Provine found that congenitally deaf people laughed at the same points in signing conversations that hearing people do in speaking conversations.

  • Laughter is, as folk wisdom says, contagious. Just listening to someone else laugh can be enough to start a person laughing.

Originally, Provine says, chimp "laughter" probably arose from the chimps' panting breathing patterns during play. Over the years, that sound evolved into the signal of social banter that it is today. Sometimes we might laugh because we've heard a rip-roaring good joke--but more often, we use laughter as a tool for social bonding.

Chuckles, snorts and belly laughs

Of course, not all laughs are the same. We all recognize a laugh when we hear it, but some are chortles, some chuckles, some guffaws and some snorts. Go to the Web site of Jo-Anne Bachorowski, PhD, and you can hear examples of them all. Bachorowski, a psychology professor at Vanderbilt University, has begun to expand on Provine's work by teasing out the differences between varieties of laughs and what those differences might mean.

In a 2001 study published in Psychological Science (Vol. 12, No. 3, pages 252-257) she and her colleagues asked college students to rate 50 taped examples of male and female laughter. The examples ranged from "voiced" laughter with an almost song-like "hahaha" or "hehehe," to "unvoiced" laughter that sounded more like a snort.

The researchers found that both male and female listeners responded much more positively to the voiced laughter than to the unvoiced laughter: They enjoyed listening to it more, said it sounded friendlier and were more likely to express interest in meeting the laugher.

These positive reactions, Bachorowski says, hint at the evolutionary purpose of laughter. We use laughter, she posits, to elicit positive reactions from other people and to communicate to them that we mean them no harm.

"Humans rely on cooperative behavior with nonkin to an extent that isn't seen in other species," she says. "But humans are also inherently competitive. So the idea is that we had to evolve some means that let others know we feel positively towards them."

Laughter, she says, is that means. But not just any laughter.

She and her colleagues believe that voiced laughter is a much more reliable indicator of a person's positive mood than unvoiced laughter. In other words, a person laughing "hahaha" probably really is happy and nonaggressive. A snorter, though, you just can't be sure about.

An as-yet-unpublished follow-up to the Psychological Science study provides more evidence for this idea. In it, Bachorowski, whose Web site is, found that autistic children--who, she says, tend to produce very honest signals to their internal states--had a much higher ratio of voiced laughter to unvoiced laughter than other children of the same age.

Next, Bachorowski says, she plans to use brain imaging to start delving into the neuroanatomical bases of laughter: For example, she wants to explore whether the parts of the brain involved in laughter are older than those involved in speech.

"This subject kind of grabs you," she says. "I don't think anyone grows up saying, 'I'm going to study laughter.' But if you stumble upon it, it sure is fun."

Further Reading

  • Bachorowski, J.A., & Owren, M.J. (2003). Reconsidering the evolution of nonlinguistic communication: The case of laughter. Journal of Nonverbal Behavior, 27, 183-199.

  • Provine, R.R. (2000). Laughter: A scientific investigation. New York: Viking.