Intergroup violence in bursts
arXiv:2112.05088
The paper analyzes video recordings of street fights and uses an adapted Ising model to explain why collective violence sometimes erupts as a rapid burst versus a slower spread, linking this to the proportion of group members unwilling to contribute to the collective goal.
Abstract
During intergroup confrontations, agitating stimuli such as opponents' threats and provocations can trigger collective violence, even without the usual mechanisms of ingroup cooperation, such as norms with sanctions. We examine video recordings of street fights between groups of young men. Their violence sometimes breaks out in a burst, wherein a majority of participants starts fighting almost simultaneously. At other times, only few group members participate and it takes them more time to do so. This difference in commencing collective violence can be understood by perceiving it as a collective action dilemma. We adapt an Ising model to show that the proportion of group members who cannot or do not want to contribute to the public good -- victory over opponents -- predicts whether violence takes the form of a burst or not.