Abstract
Infidelity is the major cause of partnership breakups across cultures and individuals with a history of infidelity are more likely to repeat it, although they may also present a greater opportunity for short-term sexual relationships. Here we have firstly investigated sex-differences in the attractiveness and perceived relationship potential of individuals who have exhibited fidelity or infidelity in a previous relationship. We also examined whether these sex differences are amplified by the neuropeptide oxytocin which promotes partner bonds but may also enhance sex-differences in social priorities. While both sexes valued faithful individuals most for long-term relationships, men were more interested in having short-term relationships with previously unfaithful individuals than women, irrespective of current relationship status. Oxytocin administration increased men’s attraction to unfaithful women and wanting short-term relationships with them, whereas women became more averse to unfaithful men and instead exhibited an even greater preference for having long-term relationships with faithful ones. The oxytocin effect on relationship-choice was only found in single individuals in line with their higher priority for finding a prospective partner. Thus, oxytocin release during courtship may first act to amplify sex-dependent priorities in attraction and mate choice before subsequently promoting romantic bonds with preferred individuals.
