In this study, we examined adults’ cardiac reactivity to repeated infant cry sounds in a genetically informative design. Three episodes of cry stimuli were presented to a sample of 184 adult twin pairs. Cardiac reactivity increased with each cry episode, indicating that subjects were increasingly sensitized to repeated infant distress signals. Non-parents showed more cardiac reactivity than parents, and males displayed a larger increase in heart rate (HR) in response to repeated cry sounds than females. Multivariate genetic modeling showed that the genetic component of adults’ HR while listening to infant crying was substantial. Genetic factors explained 37–51% of the variance in HR and similar genes influenced HR at baseline and HR reactivity to infant crying. The remaining variance in HR across the cry paradigm was accounted for by unique environmental influences (including measurement error). These results point to genetic and experiential effects on HR reactivity to infant crying that may contribute to the explanation of variance in sensitive and harsh parenting.

Although emotional responses are theorized to be important in the development of empathy, findings regarding the prediction of early empathic behavior by infant behavioral and physiological responses are mixed. This study examined whether behavioral and physiological responses to mild emotional challenge (still face paradigm and car seat task) in 118 infants at age 6 months predicted empathic distress and empathic concern in response to an empathy-evoking task (i.e, experimenter’s distress simulation) at age 20 months. Correlation analyses, corrected for sex and baseline levels of physiological arousal, showed that stronger physiological and behavioral responses to emotional challenge at age 6 months were positively related to observed empathic distress, but not empathic concern, at age 20 months. Linear regression analyses indicated that physiological and behavioral responses to challenge at 6 months independently predicted empathic distress at 20 months, which suggests an important role for both physiological and behavioral emotional responses in empathy development. In addition, curvilinear regression analyses showed quadratic associations between behavioral responses at 6 months, and empathic distress and empathic concern at 20 months, which indicates that moderate levels of behavioral responsivity predict the highest levels of empathic distress and empathic concern.