Reciprocity Outperforms Conformity to Promote Cooperation

Evolutionary psychologists have proposed two processes that could give rise to the pervasiveness of human cooperation
observed among individuals who are not genetically related: reciprocity and conformity. We tested whether reciprocity
outperformed conformity in promoting cooperation, especially when these psychological processes would promote a
different cooperative or noncooperative response. To do so, across three studies, we observed participants’ cooperation
with a partner after learning (a) that their partner had behaved cooperatively (or not) on several previous trials and
(b) that their group members had behaved cooperatively (or not) on several previous trials with that same partner.
Although we found that people both reciprocate and conform, reciprocity has a stronger influence on cooperation.
Moreover, we found that conformity can be partly explained by a concern about one’s reputation—a finding that
supports a reciprocity framework.