The Sex Connection

Because laughter is largely spontaneous and uncensored, it is a powerful probe into social relationships, writes Provine. Laughter can make people seem warm or authoritative, cooperative or ineffectual, or just plain obnoxious.

Tickling has long been the trigger that creates laughter, something even the ancients knew, says Provine. Tickling itself is an interesting phenomenon, he points out. When parents tickle an infant or a child, it's to evoke laughter.

In fact, tickling is much the same behavior as the rough-and-tumble play of apes. "Except when apes laugh, it's a pant-pant-pant kind of sound rather than ha-ha-ha," he points out.

Among adults, tickling is an important part of foreplay. "Mention tickling, and people may have an image of being held down by older brother. But they forget that tickling is also part of a rough and tumble in sack." Well, a gentler form of tickling certainly is, he clarifies.

Provine has studied male/female laughter patterns. In one series of "urban safaris," he set out to study humans in their natural habitat of shopping malls, city sidewalks, and the university student union -- documenting 1,200 laugh episodes.

His findings: Speakers laugh more than their audiences -- 46% more. The effect was even more striking when females were doing the talking. They laughed 126% more often than the guys they were talking to.

"Female speakers are enthusiastic laughers whoever their audience may be," writes Provine. "Male speakers are pickier, laughing more when conversing with their male friends than with an audience of females. The least amount of speaker laughter occurred when males were conversing with females."

The social aspect of laughing was striking, he says. People laughed about 30 times more when they were around others than when they were alone. Compare that to other social interactions: People smiled more than six times more and talked more than four times more in social than solitary situations.

Like small talk, laughter plays a somewhat similar role in social bonding, solidifying friendships and pulling people into the fold. You can define "friends" and "group members" as those with whom you laugh.

But what makes us guffaw? "Our study failed to discover The Mother of All Jokes or even her next of kin," he writes. "In fact, most laughter did not follow anything resembling a joke, storytelling, or other formal attempt at humor."

Most laughter is about playful relationships between people, he says. "Laughter is not about jokes. If you pay attention to everyday life, you laugh," he tells WebMD.