Categories and Prevalence
Our review of the history of thinking about children's handicaps has shown that, by the end of the 19th century, the broad categories of handicapping conditions had been defined. In the 20th century, thinking about classification became more formal and refined so that several classification systems have emerged. This chapter describes the main types of handicap in children and provides rough estimates of the prevalence of the various conditions.
At least as important, the chapter reviews ways in which classification systems are constructed and their uses. It concludes that current classification of handicapping conditions are more complex and confusing than one might expect at first. Moreover, current behavioral classification systems seem to be useful mainly for general assignment to treatment programs rather than for detailed planning of treatment or for analysis of causes. Some reasons for the limitations in current classification systems are reviewed in this chapter and also the next one.
Classification begins with the description of individuals. Each child has a unique pattern of physical and behavioral characteristics that can be described, and this description can be used for planning that child's treatment and education. However, this description must be done in terms of categories or dimensions that can be applied to more than one child. For instance, age, height, intelligence quotient, presence or absence of abnormal movements, degree of visual impairment, activity level, aggression, and ability to use community transportation are only a few of the almost infinite number of ways in which a child can be described.