Cash, crowds, and cooperation: The effects of population density and resource scarcity on cooperation in the dictator game

The adaptive benefits of cooperation among humans have been widely studied. However, is being cooperative always adaptive across various combinations of ecological conditions? Existing work has focused on cultural, inter-, and intra-individual predictors of cooperation yet there is a lack of research on how an individual's ecology may come into play. In this work, we focus on the interaction of two ecological factors—population density and resource scarcity—on cooperation. Population density is often accompanied by social competition for limited resources. We hypothesise that in response to cues of high (versus low) population density, people facing resource-scarcity would adaptively lower their cooperativeness, more so than those with resource abundance. Results from two studies support our hypothesis—population density lowers cooperation, but only for people who perceive lower resources or social status. Our findings provide insights that cooperation varies adaptively as a function of interacting ecological factors.