Three models of behavioral effects of genetic disorders characterized by mental retardation were compared: (1) no-specific effect model (all genetic disorders have identical behavioral outcomes); (2) totally specific model (each genetic disorder has unique outcomes); and (3) partially specific model (two or more genetic disorders share outcomes…

This rejoinder to critiques (EC 602 213-215) of the authors' article (EC 602 212) on stereotypy and self-injury in the disabled responds to specific objections raised, including misleading statements, failure to address other existing models, misunderstandings, and need to include neurochemical factors. (DB)

A three-level model explains the emergence and maintenance of rhythmic stereotypy and self-injury in disabled individuals: Level 1, internally regulated rhythmic behaviors; Level 2, stereotypy and self-injury as adaptive responses to understimulating or overstimulating environments; and Level 3, stereotypy and self-injury as learned behaviors to…