embodying both reciprocity and altruism we show that unconditional altruism towards other members attenuates the punishment … 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 …

an anonymous treatment where neither player is told at the end of the experiment which decision was selected for payment … future. We can decompose altruistic preferences into baseline altruism towards any partner and directed altruism towards … friends. Decision makers vary widely in their baseline altruism, but pass at least 50 percent more surplus to friends compared …