Trustworthiness and competitive altruism can also solve the "tragedy of the commons"

The benefits of a good reputation can help explain why some individuals are willing to be altruistic in situations where they will not receive direct benefits. Recent experiments on indirect reciprocity have shown that when people stand to benefit from having a good reputation, they are more altruistic towards groups and charities. However, it is unknown whether indirect reciprocity is the only thing that can cause such an effect. Individuals may be altruistic because it will make them more trustworthy. In this study, I show that participants in a cooperative group game contribute more to their group when they expect to play a dyadic trust game afterwards, and that participants do tend to trust altruistic individuals more than nonaltruistic individuals. I also included a condition where participants had to choose only one person to trust (instead of being able to trust all players) in the dyadic trust game that followed the cooperative group game, and contributions towards the group were maintained best in this condition. This provides some evidence that competition for scarce reputational benefits can help maintain cooperative behaviour because of competitive altruism. (C) 2004 Elsevier Inc. All rights reserved.