Emergent Prosocial Behavior During Dynamic Human Group Formation

Abstract

For scientists, policy makers, and the general population, there is increasing interest in how humans form cooperative groups. Probing the changes that emerge in cognition as group sizes increase is one important direction for understanding the evolution of large cooperative societies. However, capturing real-world dynamics of group size growth has been a historical challenge for laboratory studies. We hypothesize that humans will exhibit emergent prosocial behavior as their immediate group size increases. Using a new network-embedded-dyad prisoner dilemma task, with periodic opportunities to retain or remove group members, we find subjects consistently follow a well-performing reciprocal base policy (tit-for-tat-like) across the experimental session. However, subjects' strategies also became more forgiving and less exploitative as group size increased, with a default preference shift to cooperation. Thus, human cooperation may emerge from a desire to create and maintain larger and more cooperative groups, and multiscale strategies that consider both self-interest and group-interest.