Clustering and fighting in two-party crowds: Simulating the approach-avoidance conflict

When two large groups of people meet in the same space, many outcomes are possible, depending on the types of groups and the occasion. These outcomes range from a peaceful mingling of the two groups to the occurrence of fights and riots. Because the group processes leading to these outcomes are difficult to study experimentally, we developed a multi-agent simulation model in which the approach-avoidance conflict has been formalised in simulated actors. We worked with three different kinds of agents: hardcore, hangers-on and bystanders, the difference between them consisting in the frequency with which they scan their surroundings. Data on clustering, and 'fights' are presented for 80 simulation runs, in which group size, size symmetry and group composition were varied. The conclusions are that fights especially happen in asymmetrical large groups with relatively large proportions of hardcore members. Moreover, it appears that it are especially the hardcore group and the hangers-on that attack other agents, whereas bystanders are The paper ends with a discussion on the validity of these findings, leading us to conclude that basic aspects of rioting behaviour are quite realistically represented in our simulation model.