Jean Piaget (1896-1980) spent most of his life in his native Switzerland and in France. After finishing his PhD in biology, he studied experimental psychology. In 1920, while standardizing a French version of an English intelligence test for Alfred Binet, Piaget became fascinated by children’s wrong answers. Children of the same age seemed to reason incorrectly in the same way. He suspected that this phenomenon was a function of intellectual maturation, rather than quantity of knowledge. Piaget’s research on children’s intellectual development was guided by genetic epistemology, the study of the natural unfolding of maturational processes in organisms. For example, as an apple seed matures, it does not become more seed. Instead, it changes qualitatively—into a seedling, a sapling, and then a mature tree. Similarly, Piaget saw predictable qualitative differences in how children think about things at different ages.

Piaget wrote more than 50 books on a variety of topics, including intellectual, perceptual, and moral development in children. His basic theory is presented here in brief. While there have been many challenges to and subsequent revisions of Piaget’s theory, his work continues to be a major influence in the field of child development.

The term universal constructivist implies that all humans construct their understanding of the world in predictable ways. Piaget believed humans have a dual heredity: their physical bodies and the entire natural world. Humans are not passive organisms, but rather take an active role in their own development by acting on the physical environment. Piaget believed that mental life in infancy begins with motor activity. Piaget believed that development occurs only through interactions with the environment. “Constructivist” means that cognition has to be developed through experience; in other words, it is actively constructed by the child. “Universal” means not just that everyone goes through the same stages, but also that when someone is in a particular stage, that stage pertains to all areas of his or her cognitive development at the same time. The infant who swings an arm and grasps a toy is learning about controlling the body, the nature of objects, and the relationship between body and objects. The key concepts in Piaget’s constructivist theory include mental structures, organization, and adaptation.