Do infant Japanese macaques (Macaca fuscata) categorize objects without specific training?
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In the present study, we examined whether infant Japanese macaques categorize objects without any training, using a similar technique also used with human infants (the paired-preference method). During the familiarization phase, subjects were presented twice with two pairs of different objects from one global-level category. During the test phase, they were presented twice with a pair consisting of a novel familiar-category object and a novel global-level category object. The subjects were tested with three global-level categories (animal, furniture, and vehicle). It was found that they showed significant novelty preferences as a whole, indicating that they processed similarities between familiarization objects and novel familiar-category objects. These results suggest that subjects responded distinctively to objects without training, indicating the possibility that infant macaques possess the capacity for categorization.
KeywordsInfant Japanese macaques (Macaca fuscata) Paired-preference method Spontaneous categorization
We would like to thank Shoji Itakura, James R. Anderson, and Daisuke Kosugi for their invaluable comments on an earlier version of the manuscript. The care and use of the monkeys adhered to the 1986 version of the manual "Care and use of laboratory primates" of the Primate Research Institute of Kyoto University, and the experimental designs were accepted by the Animal Welfare and Animal Care Committee of the Institute.
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