Mating-related stimuli induce rapid shifts in fathers' assessments of infants

Abstract

A common life history theory trade-off is that which males face between mating effort and parental effort. This trade-off is observed across species, among individuals within a species, and within individuals across their lifespan. Recent studies suggest the possibility of more rapid trade-offs or motivational shifts in response to transient aspects of the social environment. We were interested in whether exposure to mating-related stimuli would negatively impact men's evaluation of parental-related stimuli and vice-versa, and whether this response would differ between fathers and non-fathers. In two separate experiments, a total of 160 heterosexual or bisexual men rated how appealing they found 40 images of attractive infants and 40 images of attractive adult females. Half of all participants viewed infant images before viewing female images, and the other half viewed female images before infant images. In both experiments, fathers rated infant stimuli as more appealing than did non-fathers when infants were presented before females, but not when infants were presented after females. That is, priming fathers with female stimuli negatively impacted their ratings of infants. On the other hand, priming men with pictures of cute infants before viewing females did not impact ratings of female pictures, in either fathers or non-fathers. Nor did priming fathers with pictures of another highly rewarding stimulus - highly appealing foods - decrease their ratings of infants. The negative effect of female pictures on fathers' subsequent ratings of infant stimuli is consistent with the possibility that the female pictures activated motivational systems related to mating effort, which in turn inhibited motivational systems related to parental effort, rendering the infant stimuli less appealing. Our findings suggest that human fathers may be susceptible to transient shifts in life history strategy as a function of their immediate social environment.