Religion, ethnicity and cooperation: An experimental study

• We report a prisoner’s dilemma experiment with a multi-cultural subject pool.
• Subjects’ religions and ethnicities were revealed to or concealed from co-players.
• Known shared identity raised cooperation, but different identity did not lower it.
• Religiosity did not affect cooperation but enhanced religious intergroup effects.

We investigate how cross-cutting ethnic and religious identities as well as the strength of individual religiosity and fundamentalism affect individual cooperation. In a repeated prisoner’s dilemma experiment, information about subjects’ religious and ethnic identities was either revealed or concealed to examine the individual and joint effects of these influences on subject decisions. While subjects’ knowledge of others’ religious and ethnic difference has no net effect on their cooperativeness, the awareness of similarity increases it. Subject religiosity and fundamentalism have no independent effect on cooperation, but they enhance ethnic and religious intergroup effects.