title: Waiting by mistake: symbolic representation of rewards modulates intertemporal choice in capuchin monkeys, preschool children and adult humans.
abstract: In the Delay choice task subjects choose between a smaller immediate option and a larger delayed option. This paradigm, also known as intertemporal choice task, is frequently used to assess delay tolerance, interpreting a preference for the larger delayed option as willingness to wait. However, in the Delay choice task subjects face a dilemma between two preferred responses: "go for more" (i.e., selecting the larger, but delayed, option) vs. "go for sooner" (i.e., selecting the immediate, but smaller, option). When the options consist of visible food amounts, at least some of the choices of the larger delayed option might be due to a failure to inhibit a prepotent response towards the larger option rather than to a sustained delay tolerance. To disentangle this issue, we tested 10 capuchin monkeys, 101 preschool children, and 88 adult humans in a Delay choice task with food, low-symbolic tokens (objects that can be exchanged with food and have a one-to-one correspondence with food items), and high-symbolic tokens (objects that can be exchanged with food and have a one-to-many correspondence with food items). This allows evaluating how different methods of representing rewards modulate the relative contribution of the "go for more" and "go for sooner" responses. Consistently with the idea that choices for the delayed option are sometimes due to a failure at inhibiting the prepotent response for the larger quantity, we expected high-symbolic tokens to decrease the salience of the larger option, thus reducing "go for more" responses. In fact, previous findings have shown that inhibiting prepotent responses for quantity is easier when the problem is framed in a symbolic context. Overall, opting for the larger delayed option in the visible-food version of the Delay choice task seems to partially result from an impulsive preference for quantity, rather than from a sustained delay tolerance. In capuchins and children high-symbolic stimuli decreased the individual's preference for the larger reward by distancing from its appetitive features. Conversely, the sophisticated symbolic skills of adult humans prevented the distancing effect of high-symbolic stimuli in this population, although this result may be due to methodological differences between adult humans and the other two populations under study. Our data extend the knowledge concerning the influence of symbols on both human and non-human primate behavior and add a new element to the interpretation of the Delay choice task. Since high-symbolic stimuli decrease the individual's preference for the larger reward by eliminating those choices due to prepotent responses towards the larger quantity, they allow to better discriminate responses based on genuine delay aversion. Thus, these findings invite greater caution in interpreting the results obtained with the visible-food version of the Delay choice task, which may overestimate delay tolerance.
authors.affiliation: CNR, Istituto di Scienze e Tecnologie della Cognizione, Unit of Cognitive Primatology and Primate Center, Via Ulisse Aldrovandi, 16/b, 00197 Rome, Italy. Electronic address: elsa.addessi@istc.cnr.it.
authors.forename: Elsa
authors.initials: E
authors.lastname: Addessi
authors.affiliation: Sapienza Università di Roma, Dipartimento di Psicologia Dinamica e Clinica, Via degli Apuli, 1, 00185 Rome, Italy. Electronic address: francesca.bellagamba@uniroma.it.
authors.forename: Francesca
authors.initials: F
authors.lastname: Bellagamba
authors.affiliation: Scuola Superiore Sant'Anna, Piazza Martiri della Libertà, 33, 56127 Pisa, Italy. Electronic address: exia.delfino@gmail.com.
authors.forename: Alexia
authors.initials: A
authors.lastname: Delfino
authors.affiliation: CNR, Istituto di Scienze e Tecnologie della Cognizione, Unit of Cognitive Primatology and Primate Center, Via Ulisse Aldrovandi, 16/b, 00197 Rome, Italy; Sapienza Università di Roma, Dipartimento di Biologia Ambientale, Piazzale Aldo Moro, 5, 00185 Rome, Italy. Electronic address: francesca.depetrillo@uniroma1.it.
authors.forename: Francesca
authors.initials: F
authors.lastname: De Petrillo
authors.affiliation: CNR, Istituto di Scienze e Tecnologie della Cognizione, Unit of Cognitive Primatology and Primate Center, Via Ulisse Aldrovandi, 16/b, 00197 Rome, Italy; Sapienza Università di Roma, Dipartimento di Psicologia Dinamica e Clinica, Via degli Apuli, 1, 00185 Rome, Italy. Electronic address: valentina.focaroli@gmail.com.
authors.forename: Valentina
authors.initials: V
authors.lastname: Focaroli
authors.affiliation: CNR, Istituto di Scienze e Tecnologie della Cognizione, Unit of Cognitive Primatology and Primate Center, Via Ulisse Aldrovandi, 16/b, 00197 Rome, Italy; AIPEPUACZ, Associazione Italiana Psicologia, Etologia, Psicobiologia Umana, Animale, Comparata e Zooantropologia, Via Olindo Malagodi, 25, 00157 Rome, Italy. Electronic address: macchitella.luigi@libero.it.
authors.forename: Luigi
authors.initials: L
authors.lastname: Macchitella
authors.affiliation: Sapienza Università di Roma, Dipartimento di Psicologia Dinamica e Clinica, Via degli Apuli, 1, 00185 Rome, Italy. Electronic address: v.maggiorelli@gmail.com.
authors.forename: Valentina
authors.initials: V
authors.lastname: Maggiorelli
authors.affiliation: Sapienza Università di Roma, Dipartimento di Psicologia Dinamica e Clinica, Via degli Apuli, 1, 00185 Rome, Italy. Electronic address: pace.beatrice@virgilio.it.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Pace
authors.affiliation: LUISS Guido Carli, Viale Pola 12, 00198 Rome, Italy. Electronic address: giulia.pecora@uniroma1.it.
authors.forename: Giulia
authors.initials: G
authors.lastname: Pecora
authors.affiliation: CNR, Istituto di Scienze e Tecnologie della Cognizione, Unit of Cognitive Primatology and Primate Center, Via Ulisse Aldrovandi, 16/b, 00197 Rome, Italy. Electronic address: rossi.sabrina82@gmail.com.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Rossi
authors.affiliation: Sapienza Università di Roma, Dipartimento di Psicologia dei Processi di Sviluppo e Socializzazione, Via dei Marsi, 78, 00185 Rome, Italy. Electronic address: agnese.sbaffi@gmail.com.
authors.forename: Agnese
authors.initials: A
authors.lastname: Sbaffi
authors.affiliation: CNR, Istituto di Scienze e Tecnologie della Cognizione, Unit of Cognitive Primatology and Primate Center, Via Ulisse Aldrovandi, 16/b, 00197 Rome, Italy. Electronic address: i.tasselli@gmail.com.
authors.forename: Maria Isabella
authors.initials: MI
authors.lastname: Tasselli
authors.affiliation: CNR, Istituto di Scienze e Tecnologie della Cognizione, Goal-Oriented Agents Lab, Via San Martino della Battaglia, 44, 00185 Rome, Italy. Electronic address: fabio.paglieri@istc.cnr.it.
authors.forename: Fabio
authors.initials: F
authors.lastname: Paglieri
mesh_terms: D000328:Adult; D000818:Animals; D002428:Cebus; D002675:Child, Preschool; D002755:Choice Behavior / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D012201:Reward
keywords: Capuchins; Delay choice; Preschool children; Self-control; Symbols; Tokens