Fertile females fight for mates by belittling the competition.© IT Stock

We're all guilty of making a snide comment about someone's appearance at one time or another. But a new study hints that women may instinctively use catty comments as a weapon in the dating game.

The research shows that when women are at the most fertile point in their monthly cycle they tend to have a lower opinion of other women's looks¹. And that's not just because of mood swings. Menstrual phase had no effect on how the same women rated the looks of men, reports Maryanne Fisher of York University in Toronto, Canada.

Fisher asked 57 women and 47 men to look at pictures of female and male faces, and rate their attractiveness on a seven-point scale from 'extremely unattractive' to 'extremely attractive'.

Whereas the men were fairly consistent in their voting, the women's votes were slightly, but significantly, affected by the stage of their menstrual cycle. Women about two or three weeks past the first day of their most recent period rated females about half a point lower than women at other points in their cycle.

Poor ratings in the study might translate to disparaging remarks in the real world, says Fisher. Looking down on others may be an effective tactic in the fight to snare an attractive man, she concludes. "If you go into a nightclub washroom, you often hear women putting other women down," she says.

Hormonal changes

"A lot of feminists don't want to admit it, but I think there's a lot of competition between women," says Charles Crawford, an evolutionary psychologist at Simon Fraser University in Burnaby, Canada. It's natural that this competition should be strongest when fertility is at a peak, he adds.

Fisher plans to do the study again to look more closely at the hormonal changes that might cause such a shift in opinion. She suspects that rising oestrogen levels are the key factor, and aims to take saliva swabs from future study volunteers to see if she's right.

"It's an interesting finding," says says Ian Penton-Voak, a psychologist at Stirling University, UK. "It suggests that women do indeed compete in this way." But he adds that it is unlikely to be such a simple story. There is probably a mix of hormones and other factors influencing the womens' votes, he says.

A recipe for loneliness

In the study, both men and women also judged the females as being generally more attractive than males. This could indicate that physical beauty is more of an asset to a woman than to a man, argues Fisher. Competition among males tends to focus more on aggression or displays of wealth or physical fitness, she adds.

If beauty really is important, then it may come as no surprise that women would want to belittle their competition's looks while promoting their own. This could even help to explain the popularity of magazines featuring photos of celebrities looking less than their best, says Fisher.

But overt caustic remarks can backfire, Fisher warns. It's fine to slag off a pop star having a bad hair day, but making fun of close friends is a recipe for loneliness. "Lots of women in the study admitted that they deliberately try to dress better than their friends," says Fisher. "But first they asked me: 'This is anonymous, right?'." 

• References

  1. Fisher, M. L. Female intrasexual competition decreases female facial attractiveness. Royal Society Biology Letters, published online, doi:10.1098/rsbl.2004.0160 (2004).