Speed-Quality Tradeoffs Shape the Structure of Decision-Making Collectives

Many human groups employ hierarchical decision-making, in which only a few individuals hold the power to make decisions for the collective. A common explanation for the prevalence of hierarchical decision-making is that it provides group-level benefits by speeding up the decision-making process. However, groups can often do better by taking more time to explore a problem space or generate ideas. These contrasting accounts suggest that hierarchical or egalitarian decision structures may emerge under different circumstances. To more clearly distinguish between these circumstances, we studied an evolutionary model of group decision-making that includes both intra-group and inter-group dynamics. We show that the emergent social structure depends critically on the trade-off between speed and decision quality: scenarios that demand rapid decisions favor the evolution of skewed, hierarchical structures, while scenarios that reward extended deliberation favor the evolution of flat, egalitarian structures. Our results suggest that, instead of inevitably becoming centralized and hierarchical, groups and organizations are likely to evolve social structures that reflect the relationship between the speed and the quality of decisions they collectively make.