Previous studies show differential patterns of brain and behavioral responses elicited by infant as opposed to adult faces, especially in women. The neural and physiological basis of mothering constitutes a distinct domain of research, with potentially important implications for maternal and infant mental health.

For this reason, we limited our current investigation on parental responsiveness to infant emotion to mothers rather than sampling parents of both sexes. Despite increasing involvement of fathers in childcare in many societies and the need for research on biological bases of paternal childcare, there are known intersex differences in the neural and hormonal bases for caregiving behaviors. To begin examining whether pupil diameter is a sensitive index of parents’ physiological responses to children’s affective cues, the present study focused on mothers’ responses to infant facial expressions. If the pupil is sensitive to mothers’ affective responses, such as heightened vigilance towards infant signals of discomfort and distress, this index may prove useful in studying and understanding the mechanisms underlying maternal sensitivity or neglect. In the current study, we extend these studies by examining whether mothers’ pupil dilation is sensitive to children’s affective cues and could, in future, serve as an accessible marker of interindividual variation in these responses. There is increasing interest in the neurocognitive bases of these capacities in parents and infants, and in the possibility that subtle variations in emotional signaling may have important influences on the quality of parent–child attachment. Parental care and parent-infant interaction relies heavily on the ability to receive and express nonverbal emotional signals through facial expressions. The results show the feasibility of using pupil diameter as a marker of mothers’ affective responses to ecologically valid infant stimuli and point to a particularly prompt maternal response to infant distress cues. Pupil response was not sensitive to the arousal level of facial expressions.

A separate control experiment with luminance-matched non-face stimuli indicated that the valence effect was specific to facial expressions and cannot be explained by luminance confounds. Pupil dilation was highly sensitive to the valence of facial expressions, being larger for negative vs. Pupillary time-series were measured from 86 mothers of young infants in response to an array of photographic infant faces falling into four emotive categories based on valence (positive vs. The current study examined pupil diameter as a potential physiological index of mothers’ affective response to infant facial expressions. Human parental care relies heavily on the ability to monitor and respond to a child’s affective states.

Normal pupil size for 9 month old