Stability of cognitive performance of children with developmental delays.

A prospective longitudinal study of the development of children with delays of unknown etiology yielded data on the stability of cognitive performance over a 6-year period. Mean age at entry was 34.2 months; mean age at exit, 109.7 months. Data reported in the present article were based on assessments using the Gesell Developmental Schedules and the Stanford-Binet Intelligence Scale. For the group as a whole, the means of the test scores over time were remarkably stable. The stability of test scores appeared to be related to the level of functioning at entry, with those children with the highest development quotients at entry making the most progress over time.