Retrieval speed, age-of-acquisition estimates, uncertainty, and semantic-dimension comparisons with mentally retarded persons.

Age-of-acquisition estimates and ratings on seven semantic dimensions by nonretarded adults were compared with the codability and retrieval speed of those items by retarded individuals. Correlational analyses indicated that age-of-acquisition estimates, codability, and retrieval speed were highly related to each other and significantly related to most of the semantic dimensions. Regression analyses revealed that codability, meaningfulness, and imagery each contributed significantly to the variance of retrieval speed. These results were compared with those of similar studies in which the lexical retrieval speed of nonretarded persons was investigated.