The present meta-analysis summarizes the international basis of evidence regarding links between psychologically meaningful risk factors and political violence outcomes among adolescents and young adults. We synthesized 422 cross-sectional effect sizes from 95 samples (67 index publications, 23 countries), using robust variance estimation. The results of seven longitudinal studies and one intervention study are discussed in a narrative manner. We detected significant effects for depression (

Introduction: Investment theories have claimed reciprocal relations between intelligence and investment traits (i.e., personality traits related to seeking out, and dealing with, cognitive challenges). However, previous research has primarily addressed the effects of investment traits on intellectual development (environmental enrichment hypothesis) and often focused on either childhood or later adulthood. The present study investigated the effects of intelligence on investment traits (environmental success hypothesis) from mid to late adolescence. Method: In a 3-year longitudinal survey (2008)(2009)(2010)(2011) covering four measurement occasions, the predictive effects of both fluid and crystallized intelligence on intraindividual change in both the achievement motive (i.e., hope for success and fear of failure) and need for cognition were examined. Overall, 476 adolescents (t 1 : M age = 16.43, SD = 0.55; 51.3% girls) from Germany participated. Results: Second-order latent growth models indicated that fluid intelligence predicted a steeper growth in hope for success (β = .40), but was unrelated to change in the other investment traits. Crystallized intelligence had no effects on the investment traits under study. Conclusions: The results contribute to the research on the bidirectionality of intelligence and investment traits and add to our understanding of personality development from mid to late adolescence. Specifically, they underline the importance of nurturing hope for success especially in individuals with lower intelligence, but also show that support for the environmental success hypothesis seems to be limited to certain investment traits.

No abstract