title: Object sorting in chimpanzees (Pan troglodytes): classification based on physical identity, complementarity, and familiarity.
abstract: In 3 experiments, 5 chimpanzees (Pan troglodytes) were tested in an object-sorting task. In Exp. 1, a triad of objects and 2 trays were presented, and the subjects were trained to place 2 identical objects onto the same tray and an odd object onto the other tray. All of the subjects were able to learn this type of sorting. In Exp. 2, the 2 complementary parts of 2-part objects were presented along with 1 neutral object. The frequency of placing the complementary parts onto the same tray significantly increased after the subjects had learned to assemble the 2 parts into 1 object. In Exp. 3, test triads consisted of familiar objects and objects there were novel to the subjects. Each subject showed a significantly high frequency of placing 2 familiar objects on the same tray although all the subjects had learned to place the same objects on separate trays in Exp. 1. The object-sorting tasks may be effective for studies of classification abilities.
authors.affiliation: Department of Behavioral and Brain Sciences, Kyoto University, Aichi, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Tanaka
mesh_terms: D000818:Animals; D001288:Attention; D003210:Concept Formation; D004193:Discrimination Learning; D005260:Female; D008297:Male; D011939:Mental Recall; D002679:Pan troglodytes / Q000523:psychology*; D010364:Pattern Recognition, Visual; D011340:Problem Solving