Joint attention, affective responsivity, and symbolic play have been identified in the last granting periods as central deficits in young autistic children. One objective of the next granting period will be the evaluation of the developmental stability of these deficits over time. A second objective will be the further definition of the deficits using two strategies: a) abilities will be examined in older children that could not be assessed in younger autistic children such as search and classification strategies, knowledge of conservation, empathetic understanding, and executive functions and b) physiological responses will be investigated in a new sample of young children to determine if these cohere with behavioral response patterns. The aim of these studies will be to determine the extent to which the identified deficits reflect disorders in attention, cognitive understanding, or response to affect. The third objective of the proposed project will be the investigation of the continuity of individual differences and predictability of subsequent social, metarepresentational, and language abilities from the psychological functions assessed in early childhood for 70 autistic and 70 mentally retarded children. Given the variability in eventual outcomes of autistic individuals, a critical aim of this project is to identify early abilities and deficits linked significantly to later capacities which are, therefore, crucial targets for early intervention.