Jean Piaget was a Swiss psychologist whose insightful descriptions of children's thinking changed the way in which we (especially educators) understand cognitive development.

Piaget's theory of cognitive development is based on the assumption that people try to make sense of the world and actively create their knowledge through direct experience with objects, people and ideas.

Maturation, activity, social transmission and the need for understanding all influence the way thinking processes and knowledge develop. In response to these influences, according to Piaget's theory, thinking processes and knowledge develop through adaptation and the organization of thought.

Piaget believed that young people pass through four stages as they develop; sensorimotor, preoperational, concrete-operational and formal-operational.
