When a woman can't help having a roving eye

If a woman finds a handsome colleague suddenly irresistible, it seems she can blame it on nature. Women at the height of fertility actively seek out sexy, good-looking men, research shows. The male partner is instinctively aware of this and tries harder to please.

The study followed the emotions and sexual desires of a group of American women who were in steady relationships. The women were asked to rate their partner's looks and sex appeal several times over the course of a month. They also underwent tests, which tracked their fertility. Analysis of the results showed that the women's desire for other men was strongest when they were most fertile.

During the days when their chance of conceiving was highest, they found friends, workmates, acquaintances and strangers increasingly attractive.

Those who rated their own partners as lacking in the looks department were the most likely to find other men more desirable, a journal reports. It seems however, that men are somehow aware of the phenomenon, with the study showing that weedier specimens turn on the charm on the days their partner is most likely to stray.

Previous studies have shown that women looking for the thrill of an affair or hoping to get pregnant are attracted to tall men. However, when they settle down, they tend to choose shorter types. It is a general phenomenon that women choose tall, good-looking men for flings. Their looks are a sign of good genes and their ability to sire healthy children. However, the initial attraction of the macho man soon wears off, with good looking men attracting more female attention and being at higher risk of having affairs. High testosterone levels could also make them moody and violent.

This means that women looking for long term relationships tend to be drawn to less attractive men, who assures commitment generally. Their lack of looks means they are less likely to stray and more likely to provide a stable home life.