Behavioral Communities and the Atomic Structure of Networks

Abstract

We develop a method of detecting the `behavioral communities' of a social network based on how people act when they choose their behaviors in coordination with their friends' behaviors. There can be multiple different `conventions' (equilibria) in which people in some parts of the network adopt a behavior while people in other parts of the network do not. We define atoms/communities to be groups of people who behave the same as each other in every convention. This provides a microfoundation for a method of detecting communities in social and economic networks. We characterize such behavioral communities in some random graphs as a function of how strongly the benefits of adopting the behavior depend on others' behaviors. We also discuss applications including: optimally seeding the diffusion of behaviors involving peer influence, detecting which demographics or nodal characteristics define a society's communities, estimating the strength of peer influence on behavior, as well as identifying missing network data by observing a series of conventions.

Keywords: Social Networks, Networks, Cohesion, Community Detection, Communities, Games on Networks, Coordination, Complementarities, Peer Effects, Peer Influence, Diffusion, Contagion, Atoms

JEL Classification: D85, D13, L14, O12, Z13