Guys, want to look sexy and get the girl? Don't smile too much. Look brooding or show a bit of shame instead. Women, ignore that advice.
Women find happy men less sexually attractive than those with expressions that show pride or hint that they have done wrong and know it, according to Canadian researchers.
The study published online Tuesday in the American Psychological Association journal Emotion showed pictures of the opposite sex to both men and women. Participants were then asked for their initial reactions on sexual attractiveness based the expressions they saw.
"Men who smile were considered fairly unattractive by women," said Jessica Tracy, a University of British Columbia psychology professor who directed the study.
"So to the extent that men think that smiling is a good thing to do if they want to be found sexually attractive our findings suggest that's not the case," Tracy said.
The men's reaction was just the opposite.
"Women who smile are absolutely very attractive. That was by far the most attractive expression women showed," Tracy said in an interview.
The researchers admit they are not sure why men and women reacted differently to smiles. In a man, a big smile may make him appear too feminine or more desperate for sex.
The study also adds fuel to the notion that women are attracted to bad boys.
"Women are attracted to guys like James Dean, Edward the vampire. The guys who are flawed, but who know it and are tortured by it," Tracy said.
A slightly downcast expression of shame is an appeasement gesture that hints at a need for sympathy.
Men also found sexual attractiveness in women whose expressions and body language hinted at shame.
The researchers stressed they looked only at initial reactions of sexual attractiveness, and were not recommending men adopt a no-smile policy for a long-term relationship.
"When people want a long-term relationship they take much more into account than sexual attractiveness. How nice a person is, is a big thing," Tracy said.
"So we're not saying, don't be a nice guy," she said.