A Risk-Reduction Model of Sharing: Role of Social Stimuli and Inequity

The present study experimentally investigated human cooperation (sharing) in a laboratory foraging task that simulated environmental variability and resource scarcity (shortfall risk). Specifically, it investigated whether a risk-reduction model of food sharing derived from the energy budget rule could predict human cooperative behavior. Participants responded on a computer task for money and were given the choice between working alone or working with others and pooling earnings. Earnings could be kept only if the sum exceeded an earnings requirement (i.e., a need level). The effects of social variables on sharing were investigated to determine whether they constrained optimal decision making. The experiments investigated choice when participants were told the partner was a computer or a (fictitious) partner (Experiment 1) and when the earnings between the participant and partner were inequitable (Experiment 2). The results showed that social variables had no effect on decision making. Instead, sharing patterns were in accord with predictions of the risk-reduction model. These results provide additional evidence that a risk-reduction model of food sharing derived from risk-sensitive foraging models may be useful for predicting human cooperation for monetary outcomes.