From the new paper "Religious Motivations for Cooperation: An Experimental Investigation Using Explicit Primes" by Rand et al (August 2012):
The role of religion in human cooperation remains a highly contested topic. Recent studies using economic game experiments to explore this issue have been largely inconclusive, yielding a range of conflicting results. In this study, we investigate the ability of religion to promote cooperation using explicit theological primes. In a first study conducted in a church, we find that subjects who report a stronger connection with a Christian religious passage about charitable giving subsequently are more likely to cooperate in a one-shot Prisoner’s Dilemma game. In a second study conducted over the Internet, we find that Christian subjects are more likely to cooperate after reading a particular Christian religious passage compared to a neutral passage, but that the particular Hindu and secular passages have no significant effect on Christians, and that none of the passages (Christian, Hindu or Secular) have an effect among non-Christians. Our results show the potential power of explicit religious exhortations for promoting cooperation, and also their selectivity.In the conclusions are some caveats.