EXPONENTIAL COLLAPSE OF SOCIAL BELIEFS OVER WEAKLY-CONNECTED HETEROGENEOUS NETWORKS

We consider a distributed social learning problem where a network of agents is interested in selecting one among a finite number of hypotheses. The data collected by the agents might be heterogeneous, meaning that different sub-networks might observe data generated by different hypotheses. For example, some sub-networks might be receiving (or even intentionally generating) data from a fake hypothesis and will bias the rest of the network via social influence. This work focuses on a two-step diffusion algorithm where each agent: i) first updates individually its belief function using its private data; ii) then computes a new belief function by exponentiating a linear combination of the log-beliefs of its neighbors. We obtain analytical formulas that reveal how the agents' detection capability and the network topology interplay to influence the asymptotic beliefs of the agents. Some interesting behaviors arise, such as the "mind-control" effect or the "truth-is-somewhere-in-between" effect.