The presence or absence of certain behaviors associated with infantile autism in severely retarded autistic and nonautistic retarded children and very young normal children.

The modified Behavior Observation Scale adapted from Freeman et al. was used to compare normal, retarded, and autistic children with very low developmental ages and to determine the types of behavior that could differentiate these three diagnostic categories of children. Examination of the data revealed that there was much more overlap between autistic and retarded children than between autistic and normal children. However, a behavioral pattern of autism could be delineated and very retarded autistic children could be distinguished from the nonautistic retarded children. The autistic behavioral pattern included subclusters of symptoms that might be interpreted as disturbances of sensory modulation and motility.