Resting respiratory sinus arrhythmia moderates the within-person relations of parental emotional expressivity and children's prosocial behaviors

Parental supportive emotional expressivity could contribute to children's prosocial behaviors, and such an effect may differ for children with different levels of resting respiratory sinus arrhythmia (RSA). This study disentangled the stable differences across dyads (i.e., between-person effects) from the dynamic associations between parental expressivity and children's prosocial behaviors within dyads (i.e., within-person effects) and determined how resting RSA functioned as a susceptibility factor in such effects. The longitudinal design consisted of three measurements with a 1-year interval performed among 208 school-aged children (48.6% girls; Han nationality) and their parents (153 mothers and 55 fathers). The initial measurement was conducted when the children were 7 years old (M_age = 7.13, SD_age = .33). Resting RSA was calculated at the first measurement; parents reported children's prosocial behaviors and parental expressivity at each of the three measurements. The results demonstrated significant between- and within-person effects of parental expressivity on children's prosocial behaviors and found a moderating role of children's resting RSA in the within-person effects. These findings suggest that children displayed more prosocial behaviors when parents showed more supportive expressivity both across and within dyads, and higher resting RSA operated as a differential susceptibility factor in the intraindividual fluctuations in parental expressivity.