Can chimpanzee infants (Pan troglodytes) form categorical representations in the same manner as human infants(Homo sapiens)?
Chizuko Murai, Daisuke Kosugi, Masaki Tomonaga, Masayuki Tanaka, Tetsuro Matsuzawa, Shoji Itakura
We directly compared chimpanzee infants and human infants for categorical representations of three global-like categories (mammals, furniture and vehicles), using the familiarization–novelty preference technique. Neither species received any training during the experiments. We used the time that participants spent looking at the stimulus object while touching it as a measure. During the familiarization phase, participants were presented with four familiarization objects from one of three categories (e.g. mammals). Then, they were tested with a pair of novel objects, one was a familiar-category object and another was a novel-category object (e.g. vehicle) in the test phase. The chimpanzee infants did not show significant habituation, whereas human infants did. However, most important, both species showed significant novelty-preference in the test phase. This indicates that not only human infants, but also chimpanzee infants formed categorical representations of a global-like level. Implications for the shared origins and species-specificity of categorization abilities, and the cognitive operations underlying categorization, are discussed.