Behavioral economics studies have shown people to have other-regarding social preferences. In the Dictator Game, for example, dictators transfer some portion of their endowment to recipients, who start out without an endowment. If people were self-interested, those assigned the role of dictator would keep all of their endowment; those assigned to be recipients would go home with nothing. In social psychology, scores of studies document the Bystander Effect, in which the likelihood of receiving help declines as the number of potential helpers increases. To reconcile pro-social preferences with the Bystander Effect, psychologists propose the notion of diffusion of responsibility: while people want to see the victim helped, they feel less of a responsibility to help when others are present and able to help. Here, we present results from two multi-player dictator games, one in the lab with real stakes (N=196) and one online with hypothetical stakes (N=215), to look for evidence of the diffusion of responsibility in an experimental economics setting. Less