Dataset Controls after Exp 2 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，而货币如何演变为交换媒介，是社会科学领域的核心研究问题。尽管非人灵长类尚未构建货币体系，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（tufted capuchin monkeys）为实验对象，对其代币选择中的数量-质量权衡展开评估，以此作为探究"代币作为强化物的可推广性"的第一步研究——而该特性正是人类货币起源背后的潜在相关影响因素。实验中，我们为卷尾猴反复提供三类各含10单位的代币，每类代币可兑换的食物组合在数量与质量上均存在差异，并借此测量卷尾猴的交换偏好。整体来看，卷尾猴会最大化其数量收益，更偏好可兑换更多食物的代币，并未表现出理性决策违背行为。不过部分个体并未最大化其质量收益，这可能源于条件估值效应（conditional valuation effects）或选择过载现象（choice overload phenomenon）——即过多的备选选项会降低决策的准确性。本研究证实了比较研究的重要价值：通过细致剖析塑造其他物种经济行为的多重构成要素，或可实现更全面的、基于进化与生态学视角的人类经济行为理解。本文属于"非人灵长类经济行为的存在与普遍性"专题专栏内容。