The bystander effect in an N-person dictator game

Dozens of studies show that bystanders are less likely to help victims as bystander number increases. However, these studies model one particular situation, in which victims need only one helper. Using a multi-player dictator game, we study a different but common situation, in which a recipient’s welfare increases with the amount of help, and donors can share the burden of helping. We find that dictators transfer less when there are more dictators, and recipients earn less when there are multiple dictators. This effect persisted despite mechanisms eliminating uncertainty about other dictators’ behavior (a strategy method and communication). In a typical public goods game, people seem to transform the situation into an assurance game, willing to contribute if certain others will too. Despite similarities, people do not treat a recipient’s welfare like a public good. Instead, people seem to transform the situation into a prisoner’s dilemma, refusing to help whatever others do.

► We study helping when a victim’s welfare increases with the amount of help.
► We used a multi-player dictator to model these helping situations.
► Dictators transfer less when there are more dictators.
► This effect persisted despite eliminating uncertainty about others’ behavior.
► People seem to treat many-to-one helping differently than other public goods.