Cooperation due to cultural norms, not individual reputation.

Increased cooperation in groups that are allowed to communicate (engage in "cheap talk") has been attributed to reputation-building and to cultural norms or culturally normal behavior. We tested these two theories by exposing groups of undergraduates to a public-goods social dilemma. Five groups were permitted to communicate via anonymous written messages that were read aloud. The groups with messaging contributed substantially more to the common good than the groups without messaging. Because the messages were anonymous, their efficacy cannot be explained by effects on reputation. Instead, the results point to the participants' histories of giving and receiving exhortations to cooperate - i.e., to culturally normal behavior (cultural norms).