Intellectual development refers here to the changes that occur, as a result of growth and experience, in a person’s capacities for thinking, reasoning, relating, judging, conceptualizing, etc. In particular it concerns such changes in children.
There are a number of different approaches to the study of intellectual development in children. As in the history of most branches of scientific knowledge, the study began with observation and description. For many years descriptive accounts of children’s thinking, reasoning, and other intellectual capacities were thoroughly mixed with descriptions of their social and emotional development and of their verbal and motor skills. Moreover, there was at first a tendency to attribute to the child mental processes that were simply miniature versions of adult thought patterns. Such early observers as Darwin (1877) were careful and deliberate, but their records often revealed the limitations of studying only one child, and the biases of the observer.
Predictably, the early, unsystematic observation of one child at a time was eventually replaced by systematic efforts to measure children’s behavior and capacities in standardized and objective ways. The growth of the mental testing movement in the first 40 years of the twentieth century testifies to the enthusiasm that was generated by the possibility of applying the precision of quantitative measurement to the task of comparing individual children and calibrating the changes that take place over the early years of life. Although observation had been supplemented by measurement, the primary purpose of these efforts remained descriptive, and the generalizations achieved were themselves only descriptions of trends and improvements that occurred consistently with increasing age.
Still more recently, since about 1950, there has been an increasing movement toward the laboratory study of the ways in which patterns of development themselves change as age changes. This recent work has been not so much concerned with the effects of age itself as with the development in children of certain functional relationships between experience and performance that have been demonstrated in human adults and have been found lacking in most infra-human species. The emphasis is on the application of laboratory controls and experimental manipulations to the study of cognitive development. The aim is to control the stimulus conditions under which behavior is observed and to explain why intellect develops, as well as describing how and when it develops.
Such an approach does not obviate the need for study of the child’s understanding as it changes with age. Rather, it relies on developmental descriptions of intellectual processes and products for clues as to when a certain level of understanding or specific intellectual accomplishment is likely to be achieved, and what repertoire of cognitive processes constitutes the means available for such an accomplishment at that age. Even the correlation of processes with products over ages, however, leaves the detailed cause-effect analysis still to be performed.
Although the present article is not primarily concerned with age changes per se, it should be noted that the description of age changes in intellectual functioning continues to thrive in two lines of research. One is the continued development and refinement of standardized tests of intelligence in order to predict an individual’s future intellectual achievement and to select, train, and guide children whenever a test-derived forecast can aid in making decisions on their behalf.
The second line of research is that of Jean Piaget and his associates on cognitive development. This large body of work has been concerned with the onto-genetic unfolding and evolution of cognitive capacities in the child, and like the work of Heinz Werner (1926), it has an organic quality and a complexity that are quite different from the empirical, item-analysis tradition of the test developers.
Both of these lines of research are structural in emphasis, i.e., they are primarily concerned with identifying the component parts or capacities of the intellect and with the organization and arrangement of these parts. The test developers are concerned with objective measurement of capacities in quantitative terms governed by a sophisticated statistics and a well-worked-out theory of measurement. The genetic epistemologists, on the other hand, have followed Piaget’s lead in attempting to describe the step-by-step development of the child’s understanding of his world as it progresses toward a formal, abstract, and logical comprehension of operations and relations in that world. Recent investigators stimulated by Piaget’s work have begun the task of isolating the conditions necessary for cognitive change and the explication of processes as well as products.
In contrast, a functional emphasis, i.e., a concern with dynamics, processes, and interrelationships, is found in the descriptions of cognitive development and in the explorations of dynamic mechanisms in cognitive change that have largely been undertaken by American behaviorists and behavior analysts and by Soviet pedagogists. These lines of research are more concerned with the processes of learning and thinking than with the structure of understanding. It is to the contributions of these functionalists that the present article is primarily devoted. It will be necessary first to summarize the most important age changes that have been described from infancy to adolescence. Consideration is then given to cognition, seen as the elaboration and selective generalization of simpler forms of learning and conditioning. Concepts such as mediation, learning set, and expectancy are discussed in relation to experimental studies of discrimination learning and discrimination reversal, concept formation, and the perceptual constancies. Curiosity and exploratory motivation are treated in relation to orienting responses and observing behavior. Research on acquired dis-tinctiveness, equivalence, and relevance of cues is presented as evidence for the importance of a general class of intervening responses, and the major role of language in this connection is stressed. Finally, consideration is given to individual differences in cognitive style, including discussion of such variables as field dependency, rigidity, reflectivity, and creativity.