The following article offers as a premise the need for innovation in special education at a time when the pace of social and educational change has increased. Suggestions offered include use of epidemiologic as well as psychometric models of retardation, and the value of basic studies of the ecology of early mental growth. Original data are presented on retarded mental development, and two conceptual schemas are offered, the first for the integration of research, service, and planning, the second for the development of instructional significance in developmental data.
Smeets et al. (1973) studied this question.