The Growth of Logical Thinking—Piaget's Contribution to Ego Psychology1

For nearly half a century, Jean Piaget and his co-workers have been studying the line of development in the child from simple perceptual patterns and stimulus-bound, automatic, rigid, unidirectional motor behavior to the mobile, abstract, hypothetico-deductive operations that characterize mature intelligent thought. They have been able to demonstrate, through a series of brilliant observations and experiments, that this developmental achievement occurs by means of a complex epigenetic sequence in which each developmental stage is derived from and represents the outer limit of equilibrium of the previous stage.

The emphasis in Piagetian theory is on progressive coördination and internalization of experimental actions so that they become increasingly reversible, mobile, and independent of the immediate perceptual field. The central role ascribed to action is, in fact, an essential feature of Piagetian theory. Piaget emphasizes that it is through his actions that the child relates to the world and comes to understand it. He has made an essential contribution to epistemology by demonstrating that intellectual development does not consist in differentiations and reorganizations in the perceptual sphere alone, which had been the prevailing view prior to his researches. He has shown that although dependent upon maturational and social-experiential factors and intimately connected with perception, intellectual development can be described in terms of step-by-step re-equilibration of action patterns that are progressively internalized, abstracted, and coördinated. He defines thought, as did Freud, as internalized, symbolic trial action.