Inhibitory Control in Early Childhood Aggression Subtypes: Mediation by Irritability.

The present study tested irritability as a mediator of inhibitory control's (IC) associations with crossed form and function aggression subtypes over one year in early childhood (N = 300, Mage = 44.70 months, SD = 4.38 months). We hypothesized lower IC would predict increases in irritability, which would in turn predict increases in aggression overall (severity) and a predominance of reactive over proactive subtypes (directionality), and considered moderation by gender. Irritability mediated IC's relations in the predicted direction for physical severity for girls only and relational severity for both genders. Lower IC predicted increases in irritability, which in turn predicted increasing predominance of reactive over proactive physical and relational aggression. The predicted indirect effect was significant for physical but not relational directionality. Findings highlight the viability of directionality scores for disentangling these effects, and that developmental associations between IC, irritability, and reactive functions of aggression are evident in early childhood.