Are capuchin monkeys ( <i>Sapajus</i> spp.) sensitive to lost opportunities? The role of opportunity costs in intertemporal choice

Principles of economics predict that the costs associated with obtaining rewards can influence choice. When individuals face choices between a smaller, immediate option and a larger, later option, they often experience opportunity costs associated with waiting for delayed rewards because they must forego the opportunity to make other choices. We evaluated how reducing opportunity costs affects delay tolerance in capuchin monkeys. After choosing the larger option, in the <i>High cost</i> condition, subjects had to wait for the delay to expire, whereas in the <i>Low cost different</i> and <i>Low cost same</i> conditions, they could perform a new choice during the delay. To control for the effect of intake rate on choices, the <i>Low cost same</i> condition had the same intake rate ratio as the <i>High cost</i> condition. We found that capuchins attended both to intake rates and to opportunity costs. They chose the larger option more often in the <i>Low cost different</i> and <i>Low cost same</i> conditions than in the <i>High cost</i> condition, and more often in the <i>Low cost different</i> condition than in the <i>Low cost same</i> condition. Understanding how non-human primates represent and use costs in making decisions not only helps to develop theoretical frameworks to explain their choices but also addresses similarities with and differences from human decision-making. These outcomes provide insights into the origins of human economic behaviour. This article is part of the theme issue 'Existence and prevalence of economic behaviours among non-human primates'.