Continuity and change in the social competence of children with autism, Down syndrome, and developmental delays.

The aims of this longitudinal study were: (1) to assess the continuity and change in diagnosis, intelligence, and language skills in children with autism, Down syndrome, and other developmental delays, (2) to specify the deficits in social competence and language skills in these children, and (3) to identify precursors in the preschool period of gains in language skills and of peer engagement in the mid-school years. The initial sample consisted of 70 children with autism, 93 children with Down syndrome, 59 children with developmental delays, and 108 typically developing children, with the first three groups of children studied when they were between 2 and 6 years of age. At follow-up, 51 children with autism, 71 children with Down syndrome, and 33 children with developmental delays were assessed at mean ages around 10-13 years.