Cortisol, hedonics, and maternal responsiveness in human mothers

New mothers are more attracted to the body odor of newborn infants than are nonmothers. In this study we investigated the relation of postpartum hormones and of prior experience with infants to this enhanced maternal attraction to infant odors. New mothers were asked to complete a hedonics task, using a pleasantness scale to provide an attraction score to different odorants presented on a cotton substrate in a 1-pt Baskin-Robbins container. Mothers were "blind" to the contents of the container. Participants also completed an extensive set of 100-item likert scales concerning their attitudes toward infants, care taking, own maternal adequacy, and other interpersonal relations. Mothers were videotaped interacting with their infants and provided salivary samples prior to the interaction. Salivary samples were assayed by radioimmunoassay (RIA) for salivary concentrations of cortisol, progesterone, and testosterone. Results show that first-time mothers with higher cortisol concentrations were more attracted to their own infant's body odor. Mothers with higher cortisol levels were also better able to recognize their own infants' odors. While cortisol was not related to attitudinal measures of maternal responsiveness, mothers with more prior experience interacting with infants exhibited both more attraction to infant odors and more positive maternal attitudes. Together, prior maternal experience and postpartum cortisol explain a significant proportion of the variance in mothers' attraction to newborn infant odors. These relations are discussed in terms of the variety of "meanings" cortisol could have during the postpartum period.