Rachlin, Howard – A Behavioral Analysis of Altruism - Alturistic acts may have been defined as costly acts that confer economic beneifts on others. (In Behavioral term: punished acts that reward others.) In prisoner's dilemma games, with human players, a significant number of players behave altruistically; their behavior benefits each of the other players but is costly to them. I propose that such altruism is based on a straightforward balancing of discounted costs to themselves againmst discounted benefits to others (social discoounting). I will describe two experiments, using the prisoner's dilemma games, that test this explanation of altruism. In one experiment, costs were held constant but thte number of others (benefiting from cooperation) varied. In another experiment, with only two players, costs were again constant but the amount of other players benefits varied directly. In both experiments, cooperation increased as benefits to the other player(s) increased.