Sex without emotional involvement: an evolutionary interpretation of sex differences.

Two samples of male (n = 243) and female (n = 298) college students completed sexual surveys, and in-depth, oral interviews were conducted with 28 highly sexually active female college students. Findings supported five predictions derived from evolutionary (parental-investment) theory. Even when females voluntarily engaged in low-investment copulation, coitus typically caused them to feel emotionally vulnerable, and to have thoughts expressing anxiety about partners' willingness to invest. For females, increasing numbers of partners correlated positively with the incidence of these feelings and thoughts; for males, these correlations were negative. Females' attempts to continue regular coitus when they desired more investment than partners were willing to give produced feelings of distress, degradation, and exploitation despite acceptance of liberal sexual morality. Increasing numbers of partners did not mitigate these reactions in females and may exacerbate them. Multiple-partner females developed techniques for dealing with their emotional reactions to low-investment copulation: They frequently tested their partners for signs of ability and willingness to invest (e.g., dominance, prowess, jealousy, nurturance), and they limited or terminated sexual relations when they perceived partners' investment as inadequate. Results were consistent with the view that the emotional-motivational mechanisms that mediate sexual arousal and attraction are sexually dimorphic.