Low socioeconomic status amplifies the perceived rarity of large rewards

Decision-making relies on heuristics derived from past experiences that likely vary with socioeconomic status. We investigate socioeconomic differences in people's reliance on a risk-reward heuristic, which exploits the tendency for larger rewards to be less probable in the world. In simulations, we show that a stronger relationship between rewards and their occurrence probability is expected under conditions of scarcity and high competition when foraging for resources. We then developed lottery and vignette tasks in which participants estimated the probability of rewards of different magnitudes. We found, and replicated, that participants with lower socioeconomic status (n = 144) rate larger rewards as less probable, but smaller rewards as more probable, than participants with higher socioeconomic status (n = 154). The same interaction was observed when comparing success probabilities of competitive foragers in environments where resources are scarce versus abundant. Telling participants about different levels of scarcity and competition in the vignettes altered their probability estimates in a manner consistent with the foraging model. We suggest that the heuristics used by people with lower socioeconomic status are a concrete adaptation to experiences of scarcity. This means psychological socioeconomic differences will persist unless actions directly tackle scarcity.