Men's interest in sex partners' status traits and commitment (investment thoughts) declines with number of sex partners and permissiveness of attitudes; women's investment thoughts do not seem to decline. Testosterone, dominance, sexual attractiveness, and number of sex partners are correlated in men but not in women. It is plausible that these sex differences are part of sexually dimorphic feedback systems. This type of feedback is consistent with both reciprocal and basal models of testosterone.