Vol.:(0123456789) 1 3 Animal Cognition https://doi.org/10.1007/s10071-018-01233-2 ORIGINAL PAPER Evolutionary origins of money categorization and exchange: an experimental investigation in tufted capuchin monkeys (Sapajus spp.) Francesca De Petrillo 1,2,3  · Martina Caroli 2  · Emanuele Gori 2  · Antonia Micucci 2,4  · Serena Gastaldi 2  · Sacha Bourgeois‑Gironde 5,6  · Elsa Addessi 2 Received: 11 June 2018 / Revised: 16 December 2018 / Accepted: 20 December 2018 © Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract 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 fexibly use tokens in dif- ferent 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 frst 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 fexibility 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-fedged monetary systems—for capuchins tokens share at least some features with human money. Keywords Money · Token · Primate · Validity · Categorization · Exchange Introduction Money is universally recognized as the most efficient medium to acquire goods and services and, at the same time, as an efective incentive that activates the same brain areas involved in reward processing. Although money is a cultural artefact without any apparent biological meaning, its power is so pervasive in human societies that it becomes crucial to understand what are the biological underpinnings of human attraction to money (Lea and Webley 2006). In this respect, a prominent basic question is how and when the brain identifes monetary validity, defned as the ability of money to be efciently exchanged for a consum- able good. To this purpose, money is considered only as a disc of metal that, upon social agreement, can be exchanged for goods and services—i.e., in terms of its purchasing power and means for exchange, not evaluating other pos- sible money properties such as unit of account and storage of value. In a study addressing the above question in adult humans, participants were tested in a one-back task, in which Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10071-018-01233-2) contains supplementary material, which is available to authorized users. * Elsa Addessi elsa.addessi@istc.cnr.it 1 Institute for Advanced Study of Toulouse, Toulouse, France 2 Istituto di Scienze e Tecnologie della Cognizione, CNR, Rome, Italy 3 Department of Psychology, University of Michigan, Ann Arbor, USA 4 Department of Psychology, University of Bologna, Bologna, Italy 5 Université Paris II, Lemma, France 6 Institut Jean Nicod, Ecole Normale Supérieure, CNRS, Paris, France