The Role of Social Identity in a Population's Adoption of Prosocial Common-Pool Behavior

Prosocial common-pool behavior - subtractable and non-excludable behavior that benefits others - is essential for the survival of any population of social individuals. The behavior, however, usually carries a cost to those who contribute it, placing them at a disadvantage with respect to those who freeride- those who do not contribute but still benefit. How populations sustain existing or adopt new prosocial common-pool behaviors remains unclear. We introduce a theoretical agent-based model and use it to study the role of social identity in a population's adoption of such behavior. Social identity is relevant because it influences the behavior of individuals in a group, including their willingness to behave prosocially. Our model simulates the emergence of multiple and dynamic social identities of agents within self-organizing groups. Our simulation results suggest that the role of social identity may depend substantially on the density of the population and the commitment level of population members to their groups; that the relationship between density, commitment, and adoption may be nuanced; that, under lower density levels, mobility between groups may be essential; and that the persistence and adoption of prosocial behavior in a population may be overwhelmingly driven by individuals who are highly committed to their groups. The results caution against the influence of two looming worldwide trends- an increase in population density and a decrease in group commitment. The results suggest that, when combined, these two trends may produce the lowest adoption levels of prosocial behavior, the adverse and population-wide repercussions of which could be catastrophic. Finally, our results suggest that social identity may play a helpful role in offsetting the consequences of these trends, implying a need for further empirical and experimental study of the subject and future consideration of incorporating the role of social identity into policy analysis and design.