Аннотация:Emotions can have important effects on performance and socioeconomic outcomes. We study a natural experiment where two teams of professionals compete in a tournament taking turns in a sequence. As the sequential order is determined by the random outcome of a coin flip, the treatment and control groups are determined via explicit randomization. Hence, absent any psychological effects, both teams should have the same probability of winning. Yet, we find a systematic first-mover advantage. Further, professionals are self-aware of their own psychological effects and, when given the chance, they rationally react by systematically taking advantage of these effects. (JEL C93, D03, D82, L83)