Money represents a cornerstone of human modern economies and how money emerged as a medium of exchange is a crucial question for social sciences. Although non-human primates have not developed monetary systems, they can estimate, combine and exchange tokens. Here, we evaluated quantity–quality trade-offs in token choices in tufted capuchin monkeys as a first step in the investigation of the generalizability of tokens as reinforcers, which is a potentially relevant factor underlying the emergence of money in humans. We measured capuchins' exchange preferences when they were repeatedly provided with 10 units of three token types yielding food combinations varying in quantity and quality. Overall, capuchins maximized their quantitative payoff, preferring tokens associated with a higher food amount, rather than showing violations of rationality. However, some individuals did not maximize their qualitative payoff, possibly because of conditional valuation effects or owing to the choice overload phenomenon, according to which too many options reduce the accuracy of choice. Our study supports the importance of comparative research to finely analyse the multiple components shaping the economic behaviours of other species, possibly to achieve a more comprehensive, evolutionary- and ecologically based understanding of human economic behaviour.

This article is part of the theme issue ‘Existence and prevalence of economic behaviours among non-human primates’.

货币是人类现代经济的基石，货币如何成为交换媒介是社会科学的一个关键问题。尽管非人类灵长类动物还没有发展出货币体系，但它们可以估计、组合和交换代币。在这里，我们评估了簇绒卷尾猴中代币选择的数量-质量权衡，作为研究代币作为强化物的普遍性的第一步，这是人类货币出现的潜在相关因素。当反复向卷尾猴提供 10 个单位的三种代币类型，从而产生数量和质量各不相同的食物组合时，我们测量了它们的交换偏好。总的来说，卷尾猴最大化了他们的定量回报，更喜欢与更高食物量相关的代币，而不是表现出违反理性的行为。然而，有些人并没有最大化他们的定性收益，可能是由于条件估值效应或由于选择过载现象，根据这种现象，过多的选择会降低选择的准确性。我们的研究支持比较研究对精细分析塑造其他物种经济行为的多个组成部分的重要性，从而可能实现对人类经济行为的更全面、基于进化和生态的理解。

本文是主题“非人类灵长类动物经济行为的存在和流行”的一部分。