The composition of multiple, stable equilibria under six models of third party intervention.

Models represent variation in pacifying and policing strategies. Models are described in the text and full mathematical details are provided in Methods 2. Those configurations for which there exist stable solutions are marked by the variables present in their locally stable equilibria. Empty columns (marked by a dash) are not stable or do not exist. Hence in the pacifying model (model 1) all strategies are stable and present at equilibrium. In the model of spontaneous policing (model 3) there are three stable equilibria, a violent equilibrium in which there are only fights and aggressive individuals present, a civil equilibrium in where there are passive individuals and police, and a police-state equilibrium in which all individuals become police.