title: Representation of the numerosities 1-9 by rhesus macaques (Macaca mulatta).
abstract: Three rhesus monkeys (Macaca mulatta) were trained to respond to exemplars of 1, 2, 3, and 4 in an ascending, descending, or a nonmonotonic numerical order (1-->2-->3-->4, 4-->3-->2--1, 3-->1-->4-->2). The monkeys were then tested on their ability to order pairs of the novel numerosities 5-9. In Experiment 1, all 3 monkeys ordered novel exemplars of the numerosities 1-4 in ascending or descending order. The attempt to train a nonmonotonic order (3-->1-->4-->2) failed. In Experiment 2A, the 2 monkeys who learned the ascending numerical rule ordered pairs of the novel numerosities 5-9 on unreinforced trials. The monkey who learned the descending numerical rule failed to extrapolate the descending rule to new numerosities. In Experiment 2B all 3 monkeys ordered novel exemplars of pairs of the numerosities 5-9. Accuracy and latency of responding revealed distance and magnitude effects analogous to previous findings with human participants (R. S. Moyer & T. K. Landaeur, 1967). Collectively these studies show that monkeys represent the numerosities 1-9 on at least an ordinal scale.
authors.affiliation: Department of Psychology, Columbia University, New York, New York 10027, USA. liz@psych.columbia.edu
authors.forename: E M
authors.initials: EM
authors.lastname: Brannon
authors.forename: H S
authors.initials: HS
authors.lastname: Terrace
mesh_terms: D000818:Animals; D003071:Cognition; D008253:Macaca mulatta / Q000523:psychology*; D008433:Mathematics; D010465:Perception; D011930:Reaction Time