Humor has been viewed as the one behavioral characteristic that men and women seek in roughly equal proportion. After all, everyone wants a partner who is entertaining and fun.

At least, that's the popular conception. However, humor researchers have long noted differences in the use and appreciation of humor. While women want to settle down with a guy who can crack a good joke, men, to a large degree, want a partner who laughs at their antics.

According to Eric Bressler, a psychologist at McMaster University in Canada, men and women don't mean the same thing when they say they value humor in a long-term partner. His research, forthcoming in the journal Evolution and Human Behavior, manipulated how funny both men and women appeared on paper. Subjects were asked to choose a potential date of the opposite . Bressler found that women want a man who is a humor "generator," while men seek a humor "appreciator."

Geoffrey Miller, an evolutionary psychologist at the University of New Mexico in Albuquerque and author of The Mind: How Sexual Choice Shaped the Evolution of Human Nature, argues that the humor divide is best understood as a result of sexual selection: Women are the choosier sex, and because they prefer funny men—a signal of cognitive fitness—men learned to deploy humor and wit to attract a mate and perhaps to outsmart other men.

"Men taunt other men with clever nicknames and insults," says John Morreal, a professor of religion at William and Mary College in Williamsburg, Virginia, who has studied humor for 25 years. "That isn't something that women do. They don't tend to play practical jokes, or engage in humor that humiliates or puts somebody down."

The basic difference is that males tend to use humor to compete with other men, while women tend to use humor to bond with others. Studies show that men more often use humor to jockey for position with other males when they are in the company of women.

The allure of male humor is so strong that female may have evolved as a signal of sexual interest—picture a woman's girlish giggles as she flirts with a man at a bar. Indeed, a German study found that when male and female strangers engaged in natural conversation, the degree to which a woman laughed while talking to a man was indicative of her interest in dating him. How much the woman laughed also predicted the man's desire to date her. On the flip side, how often a man laughed was unrelated to his interest in a woman.

Bressler says that his study indicates humor likely developed through sexual selection because it is most desirable in . Women don't care about a friend's sense of humor, whether male or female.

A woman who deploys a typically male sense of humor—one that's aggressive or competitive—is a turnoff to men, says Don Nilsen, a linguistics professor at Arizona State University in Tempe and an expert on humor. Many men feel threatened, perceiving a funny woman as a rival or worrying that they'll become a target of her sharp tongue. "I think every man in the world loves the humor, even the sexual put-down humor, of Judy Tenuta or Joan Rivers," he says. "But very few men want to marry them."

Funny guys may be attractive, Nilsen says, because they tend to be creative, "outside the box" thinkers. They also have "double vision," the ability to understand another's point of view, he says, both traits that are especially alluring to women.

Nilsen agrees with the evolutionary rationale of humor, up to a point. It doesn't explain, for example, how humor operates in long-term relationships, he argues. To say that men don't seek a funny mate is "painting with a broad brush." Men who do appreciate their female partner's humor are usually more secure, mature and educated than the average guy, he says. They hold their mates in high esteem and aren't intimidated.

A woman would do well to find a man who enjoys her humor, says Nilsen, because that's an indication of his own and willingness to be supportive.

researchers concur. Relationship expert , co-founder of the Gottman Institute in Seattle, has found that when humor plays a role in diffusing tension and conflict, marriages tend to last longer. Additional studies show that people who joke with their spouses in everyday situations tend to be happier in their marriage than couples who don't.

A playful and humorous frame of mind is protective, even when spouses don't agree about what they find to be funny.