When extraordinary injustice leads to ordinary response: How perpetrator power and size of an injustice event affect bystander efficacy and collective action

Although bystanders can play an integral role in the process of social change, relatively few studies have examined the factors that influence bystander collective action. The present research explores the effect of perpetrator power on bystander efficacy and collective action, as well as the moderating role of impact of the injustice event. Across two experiments, bystanders perceived that collective action would be less effective and were less willing to engage in collective action when a high‐power perpetrator engaged in injustice, compared with a low‐power perpetrator. These effects were moderated by impact of the injustice event, such that the effects of power were especially present under conditions of large impact (many victims), compared with small impact (fewer victims). Whereas the effect of the interaction of perpetrator power and impact on bystander efficacy was explained by perceptions of normativity of the injustice event, the effect of the interaction on bystander collective action was explained by bystander efficacy. Implications for bystander collective action and social change are discussed. Copyright © 2014 John Wiley & Sons, Ltd.