According to new US research. The study of 30 university students found that as they approached ovulation they were likely to wear trendier clothes, flash more flesh, ditch trousers in favour of skirts and don eye-catching jewellery. The findings go against the conventional wisdom that humans - unlike many animals who release powerful scents or change the colour of their skin when they are ready to mate - hide all signs of the moment they release an egg. "Near ovulation, women dress to impress, and the closer women come to ovulation, the more attention they appear to pay to their appearance," said the study's leader, Martie Haselton, of the University of California at Los Angeles. "They tend to put on skirts instead of pants, show more skin and generally dress more fashionably." Human ovulation is notoriously hard to detect, whereas in the animal kingdom the signs can be glaring. Chimpanzees famously display a swollen genital area when they are fertile. But the team said their research, published in the journal Hormones and Behavior, proved that the clues existed in humans too, even if they were more subtle. The women, who did not know what the study was about and were all in stable relationships, were photographed in their least fertile and most fertile phases. Then a group of 42 other people - just over half of them women - were asked to look at the pairs of pictures and judge in which one the woman was trying to look more attractive. Their faces were blacked out to make sure the assessment was based on their attire. The judges chose the photo taken during the the fertile phases 60% of the time, which the team said was " well beyond random chance". The study's co-author April Bleske-Rechek, a psychologist from the University of Wisconsin-Eau Claire, said what was remarkable about the effect of ovulation on women was that it was so easily observed. "In our study, the approach of ovulation had a stronger impact on the way women dressed than the onset of menstruation, which is notorious for its supposedly deleterious impact," she said. The research builds on a new body of research showing how women's behaviour changes as they approach their most fertile period. Previous studies have found that they are more inclined to flirt with men other than their partners and stray from their routine in ways that suggest they have a roving eye. "Something in women's minds is tracking the ovulation cycle," communication-studies and psychology expert Prof Haselton said. "At some level, women 'know' when they are most fertile. "And we have seen some evidence that men may at some level 'know' too - although with less certainty."