Dataset Exp 4 from Quality–quantity trade-off in the acquisition of token preference by capuchin monkeys (Sapajus spp.)

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 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’.

货币是现代人类经济的基石，而货币作为交换媒介的起源问题，亦是社会科学领域的核心议题。尽管非人灵长类尚未演化出货币体系，但它们能够对代币（Token）进行估算、组合与交换。本研究以簇绒卷尾猴为实验对象，探究其代币选择中的数量-质量权衡行为，以此作为检验「代币作为强化物的普适性」的初步尝试——而普适性正是人类货币起源背后的潜在关键影响因素。实验中，我们为卷尾猴反复提供三类各含10单位的代币，不同代币对应数量、质量各异的食物奖励，以此测量卷尾猴的交换偏好。整体而言，卷尾猴会最大化其数量收益，优先选择对应食物量更高的代币，并未表现出理性决策偏差。但部分个体并未实现其质量收益的最大化，这可能源于条件性估值效应，或是选择过载现象——即过多的选择会降低决策的准确性。本研究证实了比较研究的重要性：通过细致剖析塑造其他物种经济行为的多重维度，我们或能以更具演化与生态学视角的方式，全面理解人类的经济行为。本文隶属于「非人灵长类经济行为的存在与普遍性」专题栏目。