Also, there are large differences in the degree to which men smile less than women depending on a person's culture, ethnicity, age, or when people think they are being observed, according to the study funded by the National Science Foundation.

"It would be interesting for social psychologists and anthropologists to look at these data because the wide cultural, ethnic and other differences suggest that the sex difference is not something that is hard-wired," said Marianne LaFrance, professor of psychology at Yale and senior author of the study published this month in the journal Pyschological Bulletin. "This is not a function of being male or female. Each culture overlays men and women with rules about appropriate behavior for men and women."

LaFrance and her co-authors, Elizabeth Paluck of Yale and Marvin Hecht, a graduate student at the time, set out to examine every available study that has been done on sex differences in smiling. Ultimately, they looked at 186 research reports.

They found that women do smile more than men, but the difference is modest. "The difference is there, but it's not whopping," LaFrance said. "Indeed, there are studies that find just the opposite."

Also, the rate at which men and women differ in how much they smile is greater in the United States and Canada than in other parts of the world, like England and Australia. In the United States, there is a greater sex difference among Caucasians in smiling, but this difference virtually disappears among African-Americans.

In terms of age differences, teens show the largest sex difference in smiling. After that, the sexes converge on their smile rates. "We don't know why it maxes out among young adults," LaFrance said. "One possibility is that that is the age when the sexes are supposed to be maximally different from each other, for procreation or social purposes. After that, it's not so important."

The researchers also found that the largest sex differences in smiling occurred when men and women thought they were being observed. They smiled more similarly when they thought no one was looking.

"The logic here is when people know their behavior is being monitored, they more closely adhere to the norms for appropriate behavior for their gender," LaFrance said. "People are at their gendered best when people are looking."

Men and women also smile about the same amount when they are in the same position in terms of power, occupation or social role. Here, LaFrance surmises that the sex differences are overridden by smile norms for the role one is in, rather than with the sex one is.

However, when there is tension in the air, women more often than men try to diffuse it with a smile. "Women do what we call 'emotion work' and one of the best ways to do this is to smile to soothe hurt feelings, to restore harmony," LaFrance said.

Note: If no author is given, the source is cited instead.

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