Jean Piaget (1896-1980) was a renowned 20th-century psychologist and a pioneer in developmental child psychology. Piaget did not accept the prevailing theory that knowledge was innate or a priori. Instead, he believed a child's knowledge and understanding of the world developed empirically over time through the child's interaction with the world. His cogitations on cognitive development, in parallel with his epistemological view, gave birth to the study of genetic epistemology.

Jean Piaget's theory of cognitive development is a foundational framework in developmental psychology that outlines how children progress through distinct stages of cognitive maturity. Piaget's work emphasizes that children are active participants in their own learning, progressively constructing their understanding of the world through interaction and experience.

For nearly 30 years, his ideas were completely out of favor in behaviorist-dominated American universities; between 1932 and 1950 not a single one of his books was translated into English. But Piaget outlasted behaviorism, and by 1960 his ideas were being jubilantly rediscovered by American psychologists. Without his contributions, it is fair to say that the discipline [developmental psychology] would not exist.

Piaget's (1936, 1950) theory of cognitive development explains how a child constructs a mental model of the world. He disagreed with the idea that intelligence was a fixed trait, and regarded cognitive development as a process that occurs due to biological maturation and interaction with the environment. Piaget became intrigued with the reasons children gave for their wrong answers to the questions that required logical thinking. He believed that these incorrect answers revealed important differences between the thinking of adults and children.

In the last century, Jean Piaget proposed one of the most famous theories regarding cognitive development in children. Piaget contributions, particularly in regards to the process of education among children and transferring cognition into psychology, have had a significant effect on the science of child development.

Jean Piaget (1896-1980) is considered one of the most influential psychologists of the twentieth century, and his stage theory of cognitive development revolutionized our view of children's thinking and learning. His work inspired more research than any other theorist, and many of his concepts are still foundational to developmental psychology.

Radical behaviorism and cognitive development are two quite different theories. The most significant difference is that the two theories are based on entirely different premises. Radical behaviorism is defined by a refusal to work with the unobservable. Piaget worked with cognitive structures – a theoretical process entirely in the mind and entirely unseen. Piaget felt strongly that the learner is active, so much so that Bybee and Sund (1982, p. 57) refer to the sensorimotor stage as that of “the active child.” Behaviorism, on the other hand, is much more passive.

Piaget's theory of cognitive development, or his genetic epistemology, is a comprehensive theory about the nature and development of human intelligence. It was originated by the Swiss developmental psychologist Jean Piaget (1896–1980). To Piaget, cognitive development was a progressive reorganisation of mental processes resulting from biological maturation and environmental experience. He believed that children construct an understanding of the world around them, experience discrepancies between what they already know and what they discover in their environment, then adjust their ideas accordingly.

Jean Piaget significantly influenced the field of developmental psychology with his theory of cognitive development. His groundbreaking work provided a framework for understanding how children's thinking abilities evolve over time. Jean Piaget also founded the field of genetic epistemology, which studies the origins and development of knowledge.

At the time he started his work in the early 20th century, it was widely accepted that children were simply small adults. The mainstream thinking of the time was that children's thinking followed much the same pattern as adults. Today we know that not to be true. And that's largely thanks to Jean Piaget, the Swiss Developmental Psychologist. Piaget described children as 'little scientists' who actively learn by observing and interacting with the world around them. This was contrary to the popular thinking of the time that viewed children as 'empty vessels to be filled with knowledge.'

Piaget is considered the most influential figure in developmental psychology, though many aspects of his theories are no longer accepted by mainstream psychologists. According to Ernst von Glasersfeld, Piaget was "the great pioneer of the constructivist theory of knowing". His ideas were widely popularized in the 1960s. This then led to the emergence of the study of development as a major sub-discipline in psychology.

Jean Piaget's theory of cognitive development has been a central framework for understanding how children grow and learn. His model describes development through four sequential stages: sensorimotor, preoperational, concrete operational, and formal operational (Piaget, 1952). Each stage reflects a shift in how children think, understand, and interact with the world.