Problem-solving and conceptual behavior have for many years ranked high among the factors of intelligence. Some writers have even attempted to define intelligence in terms of problem-solving or conceptual ability. Others have employed problem-solving or conceptual tasks in their attempts to validate the construct of intelligence. The importance of this area to the study of mental deficiency would appear to be obvious. However, a perusal of the literature for the present chapter, which encompassed a period from approximately 1927 through March, 1961, has uncovered a relatively limited number and variety of studies about the basic processes of problem solving and concept formation. There appears to have been a preoccupation with the comparative study of individual differences in abstract behavior to the neglect of areas of practical, if not theoretical, importance.
After an attempt to define some of the basic terms in use in the area of problem-solving and conceptual behavior, the plan of the present chapter is to consider some problems of research methodology and then to review critically the literature on problem solving, concept formation, and abstract and concrete behavior. Only those studies that clearly include mentally deficient Ss have been reviewed in the present chapter. The reader will note the exclusion of topics such as learning set and reversal learning, which are traditionally covered in chapters on learning, but which sometimes appear in general reviews of concept formation (e.g., T. S. Kendler, 1961). A review of the research derived from Piaget's formulations has also been omitted, in view of the presence of a separate chapter dealing with his contributions. The problem of exclusion was particularly difficult, as the subject matter of the present chapter so clearly overlaps certain other areas