Esther Mertens

| 87 Role Personality in School-Based Intervention Adolescents who seemed more vulnerable to develop problems in the intra- and interpersonal domains based on their levels of Extraversion, Agreeableness, Conscientiousness, or Neuroticism appeared to benefit most from the intervention. In the present study, regardless of condition, adolescents with high levels of Extraversion increased less in sexual autonomy and decreased less in aggression, with high levels of Agreeableness also decreased less in aggression, with high levels of Neuroticism increased less in psychological wellbeing, and with low levels of Conscientiousness increased more in internalizing behavior and bullying. Hence, these levels of personality traits predicted less beneficial trajectories of change making the adolescents more vulnerable to develop problems in these outcomes. However, particularly the adolescents who were vulnerable to develop problems on a certain outcome benefitted more from R&W on this outcome than less vulnerable adolescents. This finding confirms the Risk moderation hypothesis that individuals who experience more problems can benefit more from interventions (Spoth et al., 2006). For (clinical) practice this conclusion has important implications as it suggests that the most vulnerable individuals benefit most from interventions. However, in the present study this pattern of moderation has to be interpreted with caution as the main and moderation effects were scattered across personality traits, outcomes, and conditions, and has to be replicated before stronger conclusions can be drawn. Furthermore, in contrast to our findings, previous research suggested that low rather than high levels of Extraversion and Agreeableness were related to more problems. This difference might be explained by differences in context between studies. For instance, “talkative”, a facet of Extraversion, could be considered a positive characteristic at a party, but a negative characteristic at school (Hughes et al., 2020). Extraversion showed a consistent pattern of moderating intervention effects on sexual autonomy and aggression. Individuals with high levels of Extraversion are generally sociable, interested in other people, and focused on the outer world rather than inhibited, withdrawn, and focused on one’s inner world (Pellegrino & Hilton, 2012). Their orientation towards the outer world seems to fit well with the intervention’s characteristics which require social interactions, for instance when working together in physical games and exercises, when sharing thoughts in a group, and when addressing together how the learned skills can be transferred to their daily lives. These intervention characteristics might be less suited for more inhibited and withdrawn individuals hindering them to learn from the intervention. Our findings are in line with the study of Senf and Liau (2013) who also found stronger effects for extraverted individuals in their universal intervention, but contrary to the findings of Stoltz and colleagues (2013) who found stronger effects for less extraverted individuals in their selective intervention. Perhaps high levels of Extraversion are beneficial in universal interventions, whereas low levels of Extraversion are beneficial in selective interventions. More research is needed to clarify whether the moderating role of Extraversion is dependent on the characteristics of interventions, such as the level of 4