Comparing partner could make or break your relationship

The findings suggest that how well our partner fulfils our ideal preference is not very important.

"We do not need ideal partners for relationship bliss. Instead, satisfaction appears to come, in part, from getting the best partner available to us," said one of the researchers Daniel Conroy-Beam from the University of Texas at Austin in the US.

For the study, published in the journal Evolution and Human Behavior, the researchers surveyed 259 adults -- 119 men and 140 women -- who had been in relationships for an average of seven and a half years.

Each participant rated the importance of 27 traits in an ideal mate and the extent to which they felt each trait described both their actual partner and themselves. 

Participants also reported their relationship satisfaction and happiness. 

The study discovered that satisfaction was not reliably dependent on how a partner compared with a person's idea of the perfect mate, but rather whether other potential mates better matched a person's ideal preferences.

Those with partners more desirable than themselves were satisfied whether or not their partners matched their ideal preferences. 

But, participants with partners less desirable than themselves were happy with their relationship only if their partner fulfilled their ideal preferences better than most other potential mates in the group, Conroy-Beam said.

In a follow-up study, the researchers again tested relationship satisfaction but also surveyed participants' mate retention efforts -- energy devoted to maintaining their relationships. 

They found that people with partners difficult to replace, either because their partner was more desirable than themselves or their partner more closely matched their ideal preferences than others in the group, reported being happier and devoted more effort to mate retention.

This included making themselves extra attractive for their partners and "mate guarding," or shielding their partners from mating rivals to help keep their partners, Conroy-Beam said.