R code from Are capuchin monkeys (Sapajus 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 High cost condition, subjects had to wait for the delay to expire, whereas in the Low cost different and Low cost same conditions, they could perform a new choice during the delay. To control for the effect of intake rate on choices, the Low cost same condition had the same intake rate ratio as the High cost condition. We found that capuchins attended both to intake rates and to opportunity costs. They chose the larger option more often in the Low cost different and Low cost same conditions than in the High cost condition, and more often in the Low cost different condition than in the Low cost same 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’.

经济学原理表明，获取奖励所需承担的成本会对决策选择产生影响。当个体面临小额即时奖励与大额延迟奖励的选择时，往往会因等待延迟奖励而承担机会成本——因为他们不得不放弃做出其他选择的机会。本研究评估了机会成本的降低如何影响卷尾猴的延迟容忍度。在选择大额奖励后，高成本条件组（High cost condition）的受试个体需等待延迟时长结束后方可获得奖励；而在不同低成本组（Low cost different condition）与同条件低成本组（Low cost same condition）中，受试个体可在延迟期间进行新一轮选择。为控制摄食率对选择的影响，同条件低成本组的摄食率比例与高成本条件组完全一致。研究结果显示，卷尾猴同时会考量摄食率与机会成本：相较于高成本条件组，卷尾猴在不同低成本组与同条件低成本组中选择大额奖励的概率更高；且在不同低成本组中的选择概率又高于同条件低成本组。解析非人类灵长类如何表征并运用成本进行决策，不仅有助于构建解释其选择行为的理论框架，也能为探究人类决策的异同提供参考。本研究结果可为人类经济行为的起源提供新的洞察。本文隶属于专题‘非人类灵长类经济行为的存在性与普遍性’。