Self-serving biases in beliefs about collective outcomes

Beliefs about collective outcomes play an important role in many contexts. We study biases in the formation of such beliefs. Specifically, we investigate whether self-serving biases in information processing—documented for beliefs about individual outcomes—affect beliefs about collective outcomes. In a first study, we find that people indeed exhibit self-serving biases for collective outcomes, and that such biases are similar to biases for individual outcomes. We also observe that the presence of a market institution for aggregating private information produces, if anything, slightly greater collective self-delusion. In a second study, we investigate the mechanisms driving collective self-delusion and find that anticipatory utility plays a large role, rather than ego-utility considerations.