Parent and child physiological reactivity as moderator of a proof-of-principle randomized microtrial parenting intervention

Abstract Parenting interventions can improve child adjustment, yet benefits vary. This proof-of-principle microtrial tested whether parents' and children's physiological activation moderated a brief positive feedback intervention. Participants were 101 Dutch parent–child dyads (Mage = 4.6 years, 56% boys; 97% White) randomized to feedback (n = 51) or control (n = 50). Data were collected between October 2022 and February 2025. Parenting and child behavior were coded from interaction tasks; reactivity was indexed by heart rate residualized for baseline during interaction episodes. The intervention increased positive and reduced negative parenting, particularly among reactive parents. More reactive children in the intervention group showed higher positive and lower negative behavior at posttest than controls. Tentative evidence suggested aligned parent–child susceptibility (“dual-susceptibility”). Findings warrant replication in larger preregistered trials with longer follow-up.