Evolutionary origins of money categorization and exchange: an experimental investigation in tufted capuchin monkeys (Sapajus spp.)
Money is a cultural artefact with a central role in human society. Here, we investigated whether some features of money may be traced back to the exchange habits of nonhuman animals, capitalizing on their ability to flexibly use tokens in different domains. In Experiment 1, we evaluated whether capuchins can recognize token validity. Six subjects were required to exchange with the experimenter valid/familiar tokens, valid/unfamiliar tokens, invalid tokens, and no-value items. They first exchanged a similar number of valid/familiar and valid/unfamiliar tokens, followed by exchanges of invalid tokens and no-value items. Thus, as humans, capuchins readily recognized token validity, regardless of familiarity. In Experiment 2, we further evaluated the flexibility of the token–food association by assessing whether capuchins could engage in reverse food–token exchanges. Subjects spontaneously performed chains of exchanges, in which a food item was exchanged for a token, and then the token was exchanged for another food. However, performance was better as the advantage gained from the exchange increased. Overall, capuchins recognized token validity and successfully engaged in chains of reverse and direct exchanges. This suggests that—although nonhuman animals are far from having fully-fledged monetary systems—for capuchins tokens share at least some features with human money.
KeywordsMoney Token Primate Validity Categorization Exchange
We especially thank Ludovica Foglia and Gabriele Oddi for assistance with data collection and Gabriele Schino for statistical advice. We are grateful to Gabriele Schino, Elisabetta Visalberghi, and two anonymous reviewers for their comments on a previous version of the manuscript. We thank Arianna Manciocco, Massimiliano Bianchi and Simone Catarinacci for assistance with capuchins, and Roma Capitale-Museo Civico di Zoologia and the Fondazione Bioparco for hosting the ISTC-CNR Unit of Cognitive Primatology and Primate Centre. Support from the ANR Labex IAST is also gratefully acknowledged by the authors.
This research received no funding support.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. This study complied with protocols approved by the Italian Health Ministry (DM 123/214-C to E. Addessi) and was performed in full accordance with the Directive 2010/63/EU on the protection of animals used for scientific purposes.
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