Categorisation of three-dimensional stimuli by humans and baboons: search for prototype effects
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Abstract – A symbolic matching-to-sample procedure was adopted to investigate whether 2 humans (a 27-yr-old female and a 23-yr-old male) and 2 baboons discriminate more accurately the prototypes of polymorphous categories than less typical exemplars. Ss were initially trained to discriminate between 2 categories of stimuli defined by the possession of any 2 out of 3 possible binary features. In transfer, prototypes, which contained all the 3 feature values of their categories, and novel 2-out-of-3 feature exemplars were presented for discrimination. Humans solved the task in a propositional way, and showed no evidence for a better performance with the prototypes than with other exemplars. By contrast, monkeys classified the prototypes more accurately than the other exemplars. The analysis of training performance showed, however, that their discriminations did not involve prototypical representations of the categories, but rather depended upon feature and exemplar-response associations.