Domain-specific knowledge in simple categorization tasks.

Many contemporary theories of learning and memory adopt the empiricist premise that concepts are structured according to perceptual similarity. Developmental differences in categorization tasks are thereby interpreted as the result of qualitative shifts in the capacity to attend to specific perceptual dimensions. An alternative theory is that domain-specific knowledge underlies categorization, and that even performance on simple categorization tasks is influenced by such knowledge. To test this hypothesis, adults were asked to categorize colored circles, which were described as either natural kinds or artifacts. In Study 1, the subjects were shown the actual circles; in Study 2, they were given descriptions. Adults categorized the circles differently as a function of how they were described and were influenced on subsequent choices by the demand to create "cohesive" categories. These results suggest that the developmental shifts may be due to differences in domain-specific knowledge about the nature of categorization tasks, not due to global cognitive changes. This proposal is supported by evidence from previous studies of adult categorization and children's acquisition of word meaning.