Previous research has indicated that peer popularity is associated with aggressive behavior. However, it is not yet clear whether popularity is uniquely related to different functions of aggression. In this study, we examined associations between peer-perceived popularity, and reactive and proactive aggression using a cross-sectional and a longitudinal design. Yearly sociometric measures of popularity, and reactive and proactive aggression were gathered from 266 seventh and eight grade adolescents (Mage grade 7 = 12.80, SDage  = .40). Popularity was positively correlated with proactive aggression and negatively correlated with reactive aggression, both concurrently as over time. Curvilinear trends indicated that a significant minority of low versus high popular adolescents showed both functions of aggression. Somewhat stronger effects of popularity on proactive aggression were found for boys than girls. Stably popular adolescents showed the highest levels of proactive aggression, whereas stably unpopular youth showed the highest levels of reactive aggression. Implications and directions for future research are discussed.

This study examined whether changes in children's self-reported Big Five dimensions are represented by (developmental) personality types, using a cohort-sequential design with three measurement occasions across 5 years (four cohorts, 9-12 years at T1; N = 523). Correlates of, and gender differences in, type membership were examined. Latent class growth modeling yielded three personality types: Resilients (highest initial levels on all Big Five), Overcontrollers (lowest Extraversion, Emotional Stability, Imagination), and Undercontrollers (lowest Benevolence, Conscientiousness). Gender differences in type membership were small. Warm parenting, but not overreactive discipline, in childhood was associated with type membership. The types differed in adjustment problems by the end of middle adolescence. Personality change more likely occurs at the level of dimensions within types than in type membership.

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

Background: For elementary school-children with aggressive behaviour problems, there is a strong need for effective preventive interventions to interrupt the developmental trajectory towards more serious behaviour problems. Aim: The aim of this RCT-study was to evaluate a school-based individual tailor-made intervention (Stay Cool Kids), designed to reduce aggressive behaviour in selected children by enhancing cognitive behavioural skills. Method: The sample consisted of 48 schools, with 264 fourth-grade children selected by their teachers because of elevated levels of externalizing behaviour (TRF T-score > 60), randomly assigned to the intervention or no-intervention control condition. Results: The intervention was found to be effective in reducing reactive and proactive aggressive behaviour as reported by children, mothers, fathers or teachers, with effect sizes ranging from .11 to .32. Clinically relevant changes in teacher-rated externalizing behaviour were found: the intervention reduced behaviour problems to (sub) clinical or normative levels for significantly more children than the control condition. Some aspects of problems in social cognitive functioning were reduced and children showed more positive self-perception. Ethnic background and gender moderated intervention effects on child and teacher reported aggression and child response generation. Conclusions:The results of this study demonstrate the effectiveness on outcome behaviour and child cognitions of an individual tailor-made intervention across informants under realworld conditions.

Research on gaming effects has focused on adolescence, a developmental period in which peer relationships become increasingly salient. However, the impact of peers on the effects of violent gaming on adolescents has been understudied. This study examined whether adolescents’ exposure to violent video games predicted their own and their friend's aggression one year later. Among 705 gaming adolescents, 141 dyads were identified based on reciprocated best friend nominations (73.8% male, Mage = 13.98). Actor‐Partner Interdependence Models indicated that adolescent males’ (but not females’) exposure to violent games positively predicted the aggression of their best friend 1 year later. This effect appeared regardless of whether the friends played video games together or not. The study illustrates the importance of peers in the association between violent gaming and aggression.