Just from looking at a man's face, women can sense how much he likes children, gauge his testosterone level and decide whether he would be more suitable as a one-night stand or as a husband, new research suggests.
Scientists in Chicago and California photographed men's faces and asked women to rate them on whether they seemed to like children, on their masculinity, on their physical attractiveness and on whether they seemed kind.
Then the women rated them on their potential as long- and short-term lovers.
The masculine men - those with a large jaw, prominent cheekbones, straighter eyebrows, thinner lips and a heavy beard - were found to be attractive as short-term romantic partners.
But for long-term relationships, women were more drawn to men who they thought were interested in children.
The study indicates male hormone levels and affinity for children may play a role in determining how attractive men are to women - albeit on a subconscious level.
"Our data suggest that women are picking up on facial cues that may be related to paternal qualities," said the lead author of the paper, James Roney of the University of California, Santa Barbara. "The more they perceived the men as liking kids, the more likely they could see having a long-term relationship."
The women were surprisingly adept in being able to read subtle sexual signals, Roney said.
The study's female subjects accurately determined from the photos which men had high testosterone levels - they perceived the men as more masculine. They could also pick out the men who had expressed the most interest in children.
"Our study shows that women don't just look for masculinity; they also see cues for interest in infants, and they're very accurate in judging both," said Dario Maestripieri, a behavioral biologist at the University of Chicago and co-author of the study, which appeared in Tuesday's Proceedings of the Royal Society B: Biological Sciences, a British scientific journal.
"They're attracted to one or the other, depending on whether they're interested in a short, or long-term partner."
The research suggests that our behavior may be affected by genetic programming that evolved to increase survival of the species, said Dr. Daniel Alkon, scientific director of the Blanchette Rockefeller Neurosciences Institute in Morgantown, W.Va., and Washington, D.C.
"It looks like all of us are responding to many nonverbal cues and pieces of information of which we're not really conscious that may have some origins in the hard-wired parts of the brain," Alkon said.
In the new study, researchers measured the testosterone levels of 39 male undergraduate students at the University of Chicago, based on saliva samples. They determined the men's affinity for children by asking them to choose between photos of an adult or a baby and to rate their interest.
The researchers stressed that they have no idea whether the men who expressed more interest in children would actually turn out to be good fathers.
Photos of the men were then shown to 29 female students at the University of California, Santa Barbara.
It makes sense that these women tended to be drawn to the more masculine men as short-term romantic partners, the researchers said, because high-testosterone males have a better ability to fight off disease that children might be likely to inherit.
Even though masculine-faced males might have good genes, they are seen as poor parents. Conversely, more feminine-faced males are perceived as better parents and better long-term partners.