Medical diagnosis and intelligence levels in young mentally retarded children.

The relationship of diagnosis to initial and subsequent intelligence test levels in 282 young retarded children was investigated through repeated psychometric evaluation on the Bayley Infant Scales of Mental Development or the Stanford-Binet. It was found that although aetiology relates to first test scores (or rate of initial progress), it has no bearing on changes in scores (or course of development). The implications of the surprisingly stable scores for this heterogeneous population are discussed.