Prevalence Estimates and Etiology of Learning Disabilities

Abstract

The study of the incidence of disease is known as epidemiology, a term dating back to the time of Hippocrates, who devoted one of his treatises to the subject of epidemics (H. A. Skinner, 1961). More recently, attempts have been made to include specific behavioral syndromes in epidemiological studies, as well as infectious diseases, physical defects, and accident and death rates, but these attempts have produced problems and have been met with only mixed success. In the early 1970s two papers appeared (Minskoff, 1973; Walzer & Richmond, 1973) that discussed the basic problem of trying to use the epidemiological model for estimating the prevalence of learning disabilities in the public school population. There are a number of incongruities between epidemiological studies of physically abnormal syndromes and prevalence studies of behavior deviations in mentally normal individuals, and I have discussed these at some length elsewhere (Gaddes, 1976). However, the chief difference is that the definition of physical disease conditions can usually be recognized by reliable symptoms, whereas the definition of deficit behavior, such as learning disabilities, depends on the particular local description of the disability, and this varies with the professional training of the diagnostician and the budgetary limits of the administrator arranging to treat it. Because of their behavioral emphasis, it seems that “prevalence” rather than “epidemiology” is a better term to describe non-life-threatening deficit behavioral conditions.

If the brain is indeed the principal mediating organ of behavior, and if there is a high degree of consistency across individuals in the functional anatomy of the brain, then it should be possible to

establish lawful relationships involving the relative integrity of the central nervous system on the one hand and standard forms of behavior on the other.

H. Carl Haywood (1968)