Unfounded opinion's curse

This paper investigates the role of uninformed agents in information aggregation. A group of agents, who may or may not have private information about the state, communicate through a specific communication format and vote to make the correct decision—one that matches an unobservable state—based on majority rule. We analyzed efficient equilibria under simultaneous and sequential communication formats and tested these predictions in the laboratory. When all agents were informed, information was aggregated efficiently regardless of the format. However, when some agents were uninformed, the communication format significantly affected information aggregation. Specifically, although the probability of correct group decisions closely aligned with the rational benchmark under sequential communication, it was significantly lower under simultaneous communication, as unfounded opinions undermined information aggregation. We argue that the positive effect of sequential communication can be attributed to the social facilitation effect.