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Students will be asked to distribute lottery tickets amongst themselves and their peers. Before they do so, they will be exposed to injunctive norms regarding the sharing of those tickets. They will be told that, in the past, an unknown peer decided to distribute the tickets unequally, keeping most tickets for him- or herself. Students will be randomly assigned, at the between-subjects level, to a condition that approves this unknown peer’s decision (i.e., antisocial injunctive norm condition; 25 students observed the decision, and 18 liked it) or disapproves it (control condition; 25 students observed the decision, and 18 disliked it). Afterwards, we will measure students’ own ticket sharing; will they share the tickets unequally or equally? We will also measure students’ agentic goals and narcissistic personality traits.

To investigate to what extent YouTube vloggers’ COVID related behaviors influence adolescents’ COVID related attitudes, risk perceptions, intentions to comply with COVID-regulations, and COVID-rule-setting, we will conduct a 2 × 2 between-subjects experimental study. We will expose adolescents to existing YouTube movies in which YouTube vloggers either comply or do not comply with COVID regulations. In addition, we will expose adolescents to comments of viewers who either approve or disapprove of the vloggers’ behavior. Afterwards, we will measure adolescents’ perceived importance of COVID regulation adherence, risk perceptions, intentions to comply with COVID-regulations, and COVID-rule-setting.

The prevalence of bullying worldwide is high (UNESCO, 2018). Over the past decades, many anti-bullying interventions have been developed to remediate this problem. However, we lack insight into for whom these interventions work and what individual intervention components drive the total intervention effects. We conducted a large-scale individual participant data (IPD) meta-analysis using data from 39,793 children and adolescents aged five to 20 years (Mage = 12.58, SD = 2.34) who had participated in quasi-experimental or randomized controlled trials of school-based anti-bullying interventions (i.e., 10 studies testing nine interventions). Multilevel logistic regression analyses showed that anti-bullying interventions significantly reduced self-reported victimization (d = − 0.14) and bullying perpetration (d = − 0.07). Anti-bullying interventions more strongly reduced bullying perpetration in younger participants (i.e., under age 12) and victimization for youth who were more heavily victimized before the intervention. We did not find evidence to show that the inclusion of specific intervention components was related to higher overall intervention effects, except for an iatrogenic effect of non-punitive disciplinary methods–which was strongest for girls. Exploratory analyses suggested that school assemblies and playground supervision may have harmful effects for some, increasing bullying perpetration in youth who already bullied frequently at baseline. In conclusion, school-based anti-bullying interventions are generally effective and work especially well for younger children and youth who are most heavily victimized. Further tailoring of interventions may be necessary to more effectively meet the needs and strengths of specific subgroups of children and adolescents.