Purpose of review: This review discusses design and methodological challenges specific to measuring bystander actions in the evaluation of bystander-based violence prevention programming. "Bystanders" are defined as people who are present immediately before, during and/or after a violent event, but are not a perpetrator nor the intended victim. Bystander-based violence prevention programs seek to prevent or mitigate violent events by empowering bystanders to intervene on acts of violence and social norms that promulgate violence.
Recent findings: Effective bystander-based violence prevention programs demonstrate increased bystander intentions, actions, and attitudes [Bringing in the Bystander;12 iSCREAM;33; The Men's Project;20 and Green Dot,3] lowered violence acceptance scores19,21,22,23,36 and reduced sexual violence perpetration and victimization.3••,6,20 However, bystander-based violence prevention programs are methodologically challenging to evaluate, due to the wide diversity of programs being implemented and the multifactorial and contextual nature of acts of violence.
Summary: Measures of bystander actions temporally-connected to specific, high-risk opportunities are recommended approaches to capture bystander experiences and address the methodological challenges in measuring bystander actions and evaluating violence prevention programming.
Keywords: adolescents; bystander behaviors; bystander efficacy; bystander intervention; dating violence; evaluation; interpersonal violence; sexual violence.