You might think that being in a happy relationship would make you less likely to fear potential love rivals.
But contented women have a better memory for the looks of other women than those who are unhappy, a study found.
Researchers suggested this memory boost is to guard against their partners being stolen from them.
The study also found that the more attractive a women considered herself to be, the more accurate her memory was for the faces for other women.
In their experiment, researchers from Abertay University in Dundee tested the memory for faces of women in long-term romantic relationships.
The quality of these women’s relationships had earlier been assessed via a questionnaire. In a standard memory task, women viewed a series of faces for three seconds each. They were later shown another series of faces and asked if they had seen any of them before. However, some of the faces they had previously been shown had been altered to make them more or less attractive.
Lead author Dr Christopher Watkins said the findings, published in the journal Cognition, showed that women in good relationships were particularly adept at remembering other women’s faces.
He added that women who did not consider themselves attractive were more likely to remember other women as being more beautiful than their original encounter.
He said relationship status and looks "shape both accuracy and illusions in how you remember the attractiveness of faces after a brief encounter".