Two studies investigated the presence of precursors of symbol formation in eight autistic children (nine years old) compared to matched retarded children. Results indicated that autistic Ss could form internal images but appeared to be unable to manipulate them in a purposeful and meaningful manner. (Author/CL)

Findings from relevant research applying Piaget's theory to mental retardation, psychosis, and autism are reviewed. Many autistic individuals show an arrest in operative functions at the sensorimotor functions. The early arrest interferes with subsequent development of higher-level conceptual, symbolic, and social skills. (Author)