Experimental evidence has convincingly shown the existence of reciprocal inclinations, i.e., a tendency for people to respond in-kind to hostile or kind actions. Little is known, however, about: (i) the prevalence of reciprocity in the population, (ii) individual determinants of reciprocity,...

We exploit a natural experiment in which two professionals compete in a one-stage contest without strategic motives and where one contestant has a clear exogenous psychological momentum advantage over the other in order to estimate the causal effect of psychological momentum on performance. We...