Energy Budget Rule in capuchin (Cebus [Sapajus] apella): an experimental approach

Humans sometimes make decisions that will not benefit them in economic scenarios, such as gambling, in which they choose risky options more readily over safer options. Like humans, primates will act in ways that appear to violate rationality in some chance-based situations. The mechanism behind this decision making is varied but one hypothesis to explain it, the Energy Budget Rule, predicts that a subject should make a safe choice when satiated, but, a riskier choice when more is at stake. Previous research has indicated that different primate species show varying strategies in an attempt to maximize their reward. To expand on this, we tested how capuchin monkeys’ (Sapajus apella) ability to recognize risk is affected by its energy levels. In this experiment, subjects where presented a choice between a risky option (a high-risk, high-reward) and a safe option (low-risk, moderate-reward) in two different conditions-a low energy condition (first thing in the morning, when they have low caloric intake so far for the day) and a high energy condition (afternoon, high caloric intake). Following data collection, the videos were coded to record their choices. Preliminary results show no obvious trends that support the Energy Budget Rule; however, there is individual variation in responses to the different conditions.