From Public Gatherings to the Burst of Collective Violence: An Agent-based Emotion Contagion Model

Understanding how collective actions evolve into violence is critical for guiding public safety decisions. While real- world observations of collective violence are difficult and rare, simulation models can help us to explore its evolution process. We propose an Agent-Based Emotion Contagion (ABEC) model that simulates the spread of group violence when the mechanism of contagious grievance is at work. The model is motivated by related social psychological theories of group behavior and is implemented by incorporating the epidemiological emotion contagion mechanism with crowd's game-theoretic behaviors with an agent-based approach. Our simulation model generates some crowd patterns, including local outbursts of collective violence with grievance contagion, dynamic spatial clustering of violent civilians and the nonlinear evolution of collective violence. We also explore the variations of violence evolution by varying some parameters of our model. Results show that the high-density crowds and the widespread of grievance promote violence outburst. These results suggest opportunities to curb collective violence through dispersing crowds and allaying the grievance.