The dynamics of collective action

Abstract

We elucidate the dynamics of ongoing collective action among intentional agents with diverse beliefs and imperfect information. The decisions on whether or not to contribute to the collective good depend not only on the past but also on their expectations as to how their actions will affect those of others. We show that in attempts at collective action the onset of overall cooperation can take place in a sudden and unexpected way. Likewise, defection can appear out of nowhere in very large, previously cooperating groups. These outbreaks mark the end of long transient states in which defection or cooperation persists in groups that cannot sustain it indefinitely. Computer experiments demonstrate these predictions, as well as verifying that diversity of beliefs among individuals acts as an additional source of uncertainty, instigating the outbreaks.