It’s no use being coy. If you’re looking for a fling, it might just be written all over your face.

A new study by U.K. researchers found that you can tell just by looking at someone’s face whether they’re interested in casual sex or long-term commitment. And, not surprisingly, women tend to be more attracted to the guys who look like true boyfriend material, while men are drawn to faces that seem to say “one-night stand,” the study found, published in the journal Evolution and Human Behavior.

Researchers created composite images of college students who identified themselves as either looking for a fling or love and asked 700 participants to separate the hussies from the prudes. And most of the time, their instincts were accurate – 72 percent of the participants were right more than half the time, although they couldn’t exactly explain their guesses.

 “They had the gut instinct, but they didn’t understand it,” says Lynda Boothroyd, a psychology professor at Durham University in Durham, England, and lead author of the study.

For guys face—  square jaw, prominent eyebrows and nose and smaller eyes — tends to belong to the sluttier of the sex. Men with softer features, smoother jaw lines, higher cheek bones, wider eyes were more likely to be looking for a long-term relationship.

As for women, it’s the hotties who are more likely to have flings. Both men and women who participated in the study thought that the more attractive women would be interested in something short-term, and they were right — although Boothroyd and her colleagues couldn’t pinpoint a specific facial detail about the images, just that they were slightly more classically attractive, they always had a provocative look to them.

Boothroyd’s theory sounds a little like common sense: If you’re better-looking, you simply have more opportunities to get some action. But it could arise a problem when your looking for something serious.

It could also be something of a self-fulfilling prophecy, says Caroline Keating, a psychology professor at Colgate University. Keating wasn’t involved in the Durham University study, but she has done her own research involving the psychology of facial features.

If you’re more attractive, people might expect you to have more partners. And more often than not, we fulfill those expectations people have of us.

“The way we think of ourselves is a reflection in part of how others see us,” Keating says. “So when we go out in the world, we’re looking at ourselves through a reflection of other people’s views.”

Because of the effect those expectations have on our behavior, our first impressions about people turn out to be right…

Physical appearance cues tell us more about people than we’re even consciously aware of. So in fact, we do judge a book by its cover. And the funny thing is it often works for us, and we either accept it and see where it takes us, or we turn the other cheek and find something that’s more appealing to what our needs are.