Many decisions rest on people's ability to make estimates of unknown quantities. In these judgments, the aggregate estimate of a crowd of individuals is often more accurate than most individual estimates. Remarkably, similar principles apply when multiple estimates from the same person are aggregated, and a key challenge is to identify strategies that improve the accuracy of people's aggregate estimates. Here, we present the following strategy: Combine people's first estimate with their second estimate, made from the perspective of someone they often disagree with. In five preregistered experiments (N = 6,425 adults; N = 53,086 estimates) with populations from the United States and United Kingdom, we found that such a strategy produced accurate estimates (compared with situations in which people made a second guess or when second estimates were made from the perspective of someone they often agree with). These results suggest that disagreement, often highlighted for its negative impact, is a powerful tool in producing accurate judgments.
Keywords: cognition(s); decision-making; judgment; open data; open materials; performance; prediction; preregistered.