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Men 'sniff out' potential love rivals when their partners are fertile

A weird study suggests that men are more aware of potential love rivals when their partners are at their most fertiles.

Researchers from Liverpool University showed their subjects 66 pictures of two facial types - dominant and submissive.

A composite image of a dominant face (l) next to a submissive one

They were then asked to rate the pictures for dominance, with a dominant person being defined as someone who "appeared as if they could get what they wanted". Those with partners in the most fertile stage of their menstrual cycle were more able to spot classic masculine face types - ie men with strong jaw lines, thinner lips and smaller eyes.

But those with partners who were not at risk of getting pregnant at that particular time were not.

Researcher Rob Burriss said previous studies show that during the fertile stage of their menstrual cycle women are more likely to be attracted to, and have an affair with, a masculine-looking man.

"Earlier research has shown that women are more interested in men who have a high testosterone face type - a jaw line like Arnold Schwarzenegger for example - for a short term relationship. They have better genes and are more likely to have strong children.

He surmised that men with fertile partners were sub-consciously aware of this preference change from their female partner and were reacting to it.

He added: "Groups of animals, such as chimpanzees, can live quite happily together, but when a female is ready to mate the two dominant males within the group become rivals and fight for her attention.

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