The asymmetry of altruistic giving when givers outnumber recipients and vice versa: A dictator game experiment and a behavioral economics model

The extent of altruistic giving is influenced by the numbers of givers and recipients available in a group. Two independent lines of research have addressed the effect. On the one hand, research on the bystander effect shows that a person gives less when givers outnumber recipients than if they are equal in number. On the other, studies of congestible altruism have found that a person gives more when recipients outnumber givers than if they are equal in size. An interesting question is whether giving decreases at a different rate when givers outnumber recipients than it increases the other way around. Answering the question helps illuminate whether the two effects of collective giving, which the literature has discussed separately, are governed by the same rule. We conducted a multi-person dictator game experiment to investigate people’s giving behavior in different group sizes of givers and recipients. We found that giving decreases more rapidly when givers outnumber recipients than it increases the other way around. A behavioral economics model is proposed to show how people’s belief about the selfishness of other givers can account for the asymmetry of the two effects.