Unlike his contemporaries, however, Tolman included internal mental phenomena in his perspective of how learning occurs and adopted a more holistic view of learning than was true of S-R theorists. Tolman developed his mentalistic view of learning through some ingenious adaptations of traditional behaviorist research methods. Jean Piaget's Developmental Theory Jean Piaget , a Swiss developmentalist, was also using research methods radically different from those of American psychologists. Independent of the Gestalt movement in Germany and of Tolman's work in the United States, Jean Piaget began a research program during the 1920s that has had the greatest impact on contemporary theories of cognitive development than that of any other single researcher. Piaget, a biologist, had interests in philosophy and biology and was particularly curious about epistemology.
Epistemology is a branch of philosophy that focuses on the origins of knowledge.
The recent popularity of Piaget's work may be due to it currently being the single most global theory of intellectual development. It incorporates such diverse topics as language, logical reasoning, moral judgements, and conceptions of time, space, and number. In addition, Piaget's studies with children, often involving some clever problem situations, were very revealing about the nature of children's thought. Many of Piaget's ideas are evident in contemporary cognitivism. The current notion that knowledge is structured and organized is evident in Piaget's work and in that of Tolman and the Gestaltists.