Dynamic modulation of social influence by indirect reciprocity.

Indirect reciprocity is a pervasive social norm that promotes human cooperation. Helping someone establishes a good reputation, increasing the probability of receiving help from others. Here we hypothesize that indirect reciprocity regulates not only cooperative behavior but also the exchange of opinions within a social group. In a novel interactive perceptual task (Experiment 1), we show that participants relied more on the judgments of an alleged human partner when a second alleged peer had been endorsing participants' opinions. By doing so, participants did not take into account the reliability of their partners' judgments and did not maximize behavioral accuracy and monetary reward. This effect declined when participants did not expect future interactions with their partners, suggesting the emergence of downstream mechanisms of reciprocity linked to the management of reputation. Importantly, all these effects disappeared when participants knew that the partners' responses were computer-generated (Experiment 2). Our results suggest that, within a social group, individuals may weight others' opinions through indirect reciprocity, highlighting the emergence of normative distortions in the process of information transmission among humans.