Let’s Intervene! But Only If They’re Like Us: The Effects of Group Dynamics and Emotion on the Willingness to Support Humanitarian Intervention

International relations (IR) studies on humanitarian intervention have debated both the nature and strength of intervention norms. This article contributes to this debate by exploring under what conditions individuals are willing to support military humanitarian intervention (MHI) and the psychological factors that influence whether, and the degree to which individuals support MHI. Taking a psychological approach, we hypothesized that individuals’ decision to support MHI is influenced by in-group favoritism and emotional responses to in-group suffering. We tested our theory with two experiments, each of which recruited roughly 200 American participants. Both experiments centered on the ongoing Syrian civil war and assessed Americans’ willingness to support intervention to protect different civilian groups. The results suggested that support for intervention was widespread, but not a majority view in most cases. The findings also suggested that participants exhibited slightly higher rates of support for intervention when those suffering were Christian, as opposed to Muslim. Furthermore, we found that the dynamics of support for intervention changed when chemical weapons were introduced into the scenario, which reframed the the crisis as a national security issue. Overall, our results suggest that individuals’ decisions to act upon norms can be influenced by the context of a crisis and individual level psychological factors, which have been under explored in IR scholarship on norms.