AbstractThe developmental approach toward mental retardation historically has examined whether retarded individuals behave as do nonretarded individuals. An alternative approach involves using data from handicapped populations as “experiments of nature” to provide information about typical developmental processes. Three examples of this use of mental retardation findings include examinations of sequences, rates, and cross-domain relations. Certain instances of universal sequences appear to have been replicated by findings from children with mental retardation, but in other cases mentally retarded children help illustrate the extremes to which certain individual styles of development can be taken. Changing rates of development in different types of retarded children sometimes appear due to changes in the developmental tasks facing the child, sometimes to changes in neurobiologic factors related to chronological age. Cross-domain findings from children of diverse etiologies suggest the necessity of certain, specific connections among seemingly disparate behaviors in development. The article concludes with a discussion of mental retardation research as an experiment of nature that serves to replicate and amplify existing findings as well as to spur new extensions of developmental theory.
