Men are more likely to think less of their partner after exposure to flirtatious women, according to a study published this month that puts a new twist on human mating behaviour.

The paper, which appears in the March issue of the journal Evolution and Human Behavior, is the first to show that one woman's behaviour can affect how a man views other women, including his partner.

Previous studies had shown men rated their partners lower after they were exposed to images of attractive women, said lead author and University of Lethbridge graduate student Sandeep Mishra.

While Mishra and two colleagues from McMaster University were unable to replicate those exact results, they were able to show that flirtatious behaviour could produce a similar reaction in men.

In one of the two experiments, the 87 male and 66 female test subjects watched a video of members of the opposite sex being interviewed and asked questions about politics and other non-sexual subjects.

Unbeknownst to the subjects, some of the interviewees were asked to behave in a more socially open manner by looking directly into the camera, smiling often and acting as if the viewer was the centre of attention. Other subjects viewed the interviewees behaving in a bored and disinterested manner.

The subjects were then asked to rate the attractiveness of their own partners, or, if they were single, to rate the attractiveness of other members of the opposite sex.

Men's ratings of their current partners and unattached men's rating of other women were both lower if they had viewed the more socially open videotape interviewee.

The relative openness of male interviewees had no effect on women subjects.

Results support evolutionary theory

Mishra told CBC News Online the results support theories of evolutionary psychology on the different ways in which men and women historically looked for partners.

"Women are less likely to respond to signals of intent because they are more exposed to them than men are," said Mishra. "Historically females also benefit most from finding one high quality partner, so their opinion of their partner is less likely to be swayed by exposure to an attractive male."

Reproductive success for men, on the other hand, has historically been contingent on finding and mating with a large number of females, said Mishra.

But he cautions this behaviour, while fitting with evolutionary psychological theories, does not determine how an individual will or should act.

"This doesn't mean that what is natural in biological terms is necessarily good," he said. "People still have the ability to make choices."

He suggests more awareness of these tendencies can be useful for people in relationships.

"When a man goes out and experiences these twinges of feelings, he should know there is a reason for it, and that it may not be because he is unhappy," he said.

"These behaviours can be superseded and don't have to shape the way we behave."