A man's square jaw, large nose and small eyes may be all it takes to convince a woman he's only interested in a one-night stand, a new study from the United Kingdom suggests.

In a Durham University-led study, researchers found that potential mates can judge whether a love interest is interested in casual sex or ready to move in their toothbrush based on their facial features — and will use this information to select a partner.

The computer-manipulated image on the right depicts a man more likely to be interested in a short-term sexual relationship, while the one on the left is a better long-term prospect, researchers say.
(Image provided by Durham University)

"Observers are broadly able to identify individuals who are more likely to be interested in short- or long-term relationships," the researchers wrote in the study, published Wednesday in the journal Evolution and Human Behaviour.

"Furthermore, this information may be used by women to avoid men who are less likely to engage in a long-term relationship, potentially maximizing the possible benefits of women's choices for long-term partners."

The study also found that men and women are looking for opposite things when it comes to relationships, with men seeking women who are open to casual or short-term flings while women look for potential mates.

A woman with features like those on the right is more likely to be interested in a casual fling, the research suggests.
(Image provided by Durham University)

Researchers from Durham, St. Andrews and Aberdeen universities conducted two studies asking more than 700 heterosexual participants to judge facial photos for attractiveness and attitudes toward sex. The photos, all of real people in their 20s, were manipulated to reflect strong features associated with sexual openness or commitment.

These judgments were then compared with the actual attitudes of the photographed individuals, based on data from questionnaires.

Casual females more attractive, males less

The researchers found that the participants could generally judge whether the individual would be up for a one-night stand or commitment. 

Additionally, females open to flings were judged to be more attractive, while casual males were deemed less attractive. 

Men with squarer jaws, larger noses and smaller eyes were most open to casual sex, and were generally perceived as being more masculine than the men pegged as mate material. Previous research has indicated that women see masculine men as more likely to be unfaithful and worse parents.

However, the study noted, the participants were not always confident in their judgments.

"Our results suggest that although some people can judge the sexual strategy of others simply from looking at their face, people are not always sure about their judgments, possibly because the cues are very subtle," explained lead author Lynda Boothroyd, from Durham's psychology department, in a release.

"This shows that these initial impressions may be part of how we assess potential mates — or potential rivals — when we first meet them. These will then give way over time to more in-depth knowledge of that person, as you get to know them better, and may change with age."

The research was funded by the Medical Research Council and the Economic and Social Research Council.