Uses of the Bayley mental scale with nonambulatory profoundly mentally retarded children

A set of 45 mental scale items from the Bayley Scales of Infant Development was administered by two testers to 33 nonambulatory, profoundly mentally retarded subjects. Interobserver agreement was high for overall scores and for 42 of 45 individual items. Total number of items passed was significantly correlated with activity level. Division of these items into a stimulus set and a response set provided a qualitative description of performance that supported previous research indicating that these individuals have deficits in exploratory motivation and perceptual curiosity. Bayley raw scores predicted success in conditioning programs, suggesting that this test is useful for educational programming.