Contingent parental investment: an evolutionary framework for understanding early interaction between mothers and children

Evolutionary psychology predicts that mothers invest differentially in their children as a function of (a) cues to the child's reproductive value and (b) their own access to caregiving resources. In contrast to the traditional additive model of these effects, a contingent model was tested in which high-risk offspring were expected to receive either more or less investment than low risk offspring—based on maternal resources. In a prospective test of this model, we measured children's premature status at birth as a cue to their reproductive risk and mother's postpartum depressive symptoms as an indicator of depleted attentional, emotional, and cognitive resources. As predicted, (1) mothers with low resources showed greater investment in low-risk than high-risk children, and (2) mothers with higher resources showed greater investment in high-risk than low-risk children. In addition, older primiparous mothers (in contrast with younger mothers or multiparous older mothers) manifested high investment in high-risk children. No reliable support was found for the Trivers–Willard hypothesis.