Is altruism bad for cooperation?

Some philosophers and social scientists have stressed the importance for good government of an altruistic citizenry that values the well being of one another. Others have emphasized the need for incentives that induce even the self interested to contribute to the public good. Implicitly most have assumed that these two approaches are complementary or at worst additive. But this need not be the case. Behavioral experiments find that if reciprocity-minded subjects feel hostility towards free riders and enjoy inflicting harm on them, near efficient levels of contributions to a public good may be supported when group members have opportunities to punish low contributors. Cooperation may also be supported if individuals are sufficiently altruistic that they internalize the group benefits that their contributions produce. Using a utility function embodying both reciprocity and altruism we show that unconditional altruism towards other members attenuates the punishment motive and thus may reduce the level of punishment inflicted on defectors, resulting in lower rather than higher levels of contributions. Increases in altruism may also reduce the level of benefits from the public project net of contribution costs and punishment costs. The negative effect of altruism on cooperation and material payoffs is greater the stronger is the reciprocity motive among the members.