Sequential Sampling by Individuals and Groups: An Experimental Study

Many committees—juries, political task forces, etc.—spend time gathering costly information before reaching a decision. We report results from lab experiments focused on such dynamic information-collection processes, as in sequential hypothesis testing. We consider decisions governed by individuals and groups and compare how voting rules affect outcomes. Several insights emerge. First, average decision accuracies approximate those predicted theoretically, but these accuracies decline over time: Participants display nonstationary behavior. Second, groups generate markedly different outcomes than individuals, with majority rule yielding faster and less accurate decisions. In particular, welfare is higher when sequential information is collected in groups using unanimity. (JEL C83, D71, D72, D83)