Social Structure Shapes Consensus Decision-Making Norms in Small-Scale Societies: An Agent-Based Model Perspective

Humans are uniquely capable of reaching consensus within large, hierarchically structured societies. Yet the pathways by which consensus emerges, especially under constraints imposed by social organization, remain poorly understood. We use agent-based modeling to explore how marriage structure, social group nesting, and decision-making norms can shape a group’s ability to reach consensus. In our model, simulated agents are embedded in multilevel social networks and possess noisy information. Decisions are spread via three different cascades using one of several interaction norms. We find that family formation via marriages, especially when clustered within kin units, impedes consensus by slowing the rate of information diffusion and elevating informational entropy. In contrast, increasing the size of nested subgroups in a multilevel network reduces category overlap and promotes consensus. Finally, decision-making norms that bypass early-stage clustering through the formation of coalitions or representative bodies lead to faster group decisions. These results offer insights into how consensus dynamics are shaped by social structure and provide a theoretical bridge between research on network topology, collective intelligence, and human social evolution.