THE APPLICATION OF PIAGET'S THEORY TO RESEARCH IN MENTAL DEFICIENCY
Piaget's theory deals with the process of intellectual development. The object of the theory is to trace the evolution of abstract thinking from its origins in the sensorimotor behavior of infancy through the intermediate forms. This has been done by observation of the behavior of infants and by study of the concepts that older children have about various aspects of reality. Piaget's interest lies in the kind of psychological operation that leads to a result rather than in the fact of success or failure alone, and the aim of the investigation is to interpret the behavior and not merely to make an inventory of items of behavior that appear at successive ages. Consequently, the theory provides a conceptual framework from which to study the behavior of intellectually subnormal individuals.
The techniques that have been devised to investigate cognitive processes are quite distinctive, and they have brought to light new facets of the thinking of normal children; they provide a similar opportunity in the field of mental deficiency. The theory postulates a sequence of intellectual developments. Since the important feature is the order of the steps and not the age at which they are attained, this approach can be applied to individuals whose rate of development is extremely slow. It offers the means of placing them on an ordinal scale (of development from birth onward) so that age comparisons can be avoided. The type of manipulations of objects and the type of thinking shown in problem solving are more important than particular responses. This is useful in view of the prevalence of sensory and motor defects in mental deficiency: comparable results can be obtained for physically handicapped and nonhandicapped individuals.
Piaget's views have provoked considerable controversy, some of which