The purpose of the present study was to determine which behavioral and physical phenotypes would be most likely to divide the ASD population into discrete subgroups. The taxometric methods of Maximum Covariance (MAXCOV) and Minus Mean Below A Cut (MAMBAC) were employed to test for categorical versus continuous variation of each phenotype across…

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)