Autism and Piaget's theory: are the two compatible?

Autism is interpreted in Piagetian terms with particular reference to the question of whether the atypical cognitive development represents an exception to the similar sequence hypothesis. Findings from relevant research applying Piaget's theory to mental retardation, psychosis, and autism are reviewed. The apparent exceptions to the hypothesis presented in autistic individuals are explained by Piaget's two-factor theory of figurative versus operative functions. Many autistic individuals show an arrest in operative functions at the sensorimotor level while continuing to progress in figurative functions. The early arrest interferes with subsequent development of higher-level conceptual, symbolic, and social skills. Questions for research are offered.