Development of conceptual knowledge in children with mental retardation.

Nine and 14-year-old children with mild mental retardation and children without mental retardation matched for mental and chronological age were first shown a novel category made up of five visual figures. They were then given a recognition test with a set containing the previously presented figures, novel category members, and the category prototype. The relative contribution of prototypical and exemplar-specific information to subjects' performance on the recognition test was evaluated. Results showed that the children without mental retardation employed both forms of information in arriving at a recognition decision whereas both of the retarded groups tended to rely only on prototype information. Use of exemplar-specific information was also found to be positively correlated with IQ and, in particular, with measures of short-term memory span.