Indirect reciprocity and prosocial behaviour: evidence from a natural field experiment

Some of the greatest human achievements are difficult to imagine without prosociality. This article employs a natural field experiment to investigate indirect reciprocity in natural social interactions. We find strong evidence of indirect reciprocity in one-shot interactions among drivers. Subjects for whom other drivers stopped were more than twice as likely to extend a similar act to a third party. This result is robust to a number of factors including age, gender, social status, presence of onlookers, and the opportunity cost of time. We provide novel evidence for the power of indirect reciprocity to promote prosocial behaviour in the field.