Sex differences in sexual psychology produce sex-similar preferences for a short-term mate.

We explored aspects of men's and women's short-term sexual psychology as a function of a potential short-term partner's relationship status. A total of 209 men and 288 women reported how likely they would be to pursue a casual sexual relationship with an attractive member of the opposite sex who was (1) married, (2) not married but has casual sexual partners, or (3) not married and has no casual sexual partners. Guided by sperm competition theory, we predicted and found that men prefer short-term sex partners who are not already involved in relationships and hence present a relatively low risk of sperm competition. Because women sometimes use short-term sexual relationships to acquire long-term partners, we predicted and found that women prefer short-term sexual partners who are not already involved in relationships and hence present relatively greater promise as a potential long-term partner. Finally, across each of the three levels of the imagined partner's relationship status, men reported a greater likelihood than did women of pursuing a casual sexual relationship. Discussion addressed methodological limitations and directions for future work.