A new study suggests it is the less attractive ladies who are responsible for the greatest heartache.

一项新研究指出，最难守住的其实是不漂亮的女人。

When US researchers followed more than 200 married couples for three-and-a-half years, they discovered that women who considered themselves attractive were far more likely to be faithful.

They also found that women who had been more promiscuous in the years before their marriage were less likely to cheat.

In contrast, less-attractive females who had limited sexual experience were more likely to engage in extra-marital entanglements.

The researchers from Florida State University followed 233 newly married couples documented intimate details about their relationships, including marital satisfaction, long-term commitment, whether they had engaged in infidelity and if they were still together.

Writing in the Journal of Personality and Social Psychology lead author Jim McNulty said: "Specifically, own attractiveness was negatively associated with infidelity among women, but not men, suggesting that less attractive women were more likely to engage in infidelity.

"Men were more likely to engage in an infidelity when their partners were less attractive. This latter sex difference is consistent with evidence that partner attractiveness is more important to men than it is to women."

Surprisingly, the researchers found people satisfied with sex in their relationship were more likely to cheat, perhaps suggesting they felt more positive about sex in general and would seek it out regardless of how they felt about their main relationship.