Reassessment of Category Knowledge in Retarded Individuals

We investigated retarded individuals' knowledge of conceptual categories as reflected by semantic priming effects. In the first experiment, retarded individuals were shown pairs of pictures, one picture at a time, and asked to name each picture as rapidly and accurately as possible. The pictures in each pair were objects that were either categorically related or unrelated. The major finding was that second pictures in related pairs were named significantly faster than those in unrelated pairs. This reduction in naming-latency, or priming effect, was interpreted as indicating that information about categorical relationships is established in the memory structure of retarded individuals. In the second experiment, subjects were again given the picture-naming task plus two concept-usage tasks designed to test the recognition and verbalization of categorical relationships. Correlational analyses indicated that while performance on both usage tasks varied with intelligence, neither intelligence nor category usage correlated with the magnitude of the priming effect. This suggests that intelligence-related differences in category usage do not result from corresponding differences in conceptual competence but, rather, are related to the ability to use category information that is potentially available.