Child Personality as Moderator of Outcome in a School-based Intervention for Preventing Externalising Behaviour

studying moderators of intervention effects is essential to elucidate what works for whom. The present studyinvestigated whether child personality moderates short-term and follow-up effects of an individualised preventiveschool-based intervention for children with externalising behaviour. The sample consisted of 48 schools, with 264fourth-grade children displaying externalising behaviour (Mage= 10.2 years), randomly assigned to the intervention(n = 191) or no intervention control (n = 73) condition. Teachers and children reported at pretest, posttest andfollow-up test about reactive and proactive aggression. Child personality was assessed by teachers at pretest. Childconscientiousness moderated short-term intervention effects, indicating that more organised and planful childrenbenefited more from the intervention. Child extraversion moderated both short-term and follow-up interventioneffects, with low extraverted children showing larger effects. These results affirm the importance of including personalityas moderator of intervention effects in future studies, as interventions adapted to specific child traits might yield larger