Results of a new study find sex differences in smiling tend to disappear when men and women find themselves in the same occupational or social role.
"We are trying to understand why there appears to be a sex difference in how much men and women smile," says Marianne LaFrance, a professor of psychology at Yale University and lead author of the study.
LaFrance notes that while there is no controversy about the tendency of women to smile more than men, there is a debate about why.
"We reviewed every study that has ever been done that we could find that measured how much men and women smiled," says LaFrance. There were 186 studies in all, which included thousands of people from North America, South America, Europe, Asia and Australia.
The research appears in the March issue of Psychological Bulletin.
LaFrance and her colleagues considered many factors that might be responsible for the gender difference. "In some studies we found considerable national and ethnic differences in smiling between men and women," she says.
For example, "the French think that most Americans are dopey because they are smiling all the time," LaFrance says. In France, smiling is not practiced among strangers but is reserved for people with whom one has some relationship, she adds.
In the United States, the difference in smiling between men and women is greater among whites than among blacks or Asians. "This leads us to conclude that smiling, while inborn, is also culturally determined," LaFrance says.
The researchers also found the difference between how much men and women smiled depends on whether they are being observed. "When men and women knew that they were being observed, the sex difference was much larger, but disappeared if they believed they were alone," she says.
This happens because both men and women are trying to conform to gender norms of behavior, LaFrance adds.
When you put men and women in the same role or occupation, the differences in smiling behavior also tend to disappear. This suggests, to LaFrance, that when people are in the same social role or have the same social power, they tend to behave in accordance with what that role defines as appropriate behavior, and the sex differences in smiling tend to recede.
"We did find that the sex differences increased when there was social tension or negative emotion. And then women smiled significantly more than men. This may be because it is a woman's task to do 'emotion work' -- restore harmony, reduce tension and make nice, and one way that can be done is by smiling," LaFrance says.
Smiling is a good thing to study because every culture practices it, she notes. "All babies, even those born blind and deaf, smile. Humans are prepared to smile, but what is interesting is how smiling is affected by gender, culture and power," LaFrance says.
The more we understand about when, why and how much people smile, the more we know about customs, norms and expectations, she says.
Carol Magai, a psychology professor from Long Island University, agrees with LaFrance that smiling is inborn but culturally modified, and the sex difference disappears when men and women are in the same situations.
"It is obvious for any kind of emotionally expressive behavior that the basic templates are inborn, but the different ways of expressing emotion are learned as part of familial, social and cultural patterns," Magai says.