Jean Piaget, a pioneer in the study of child intelligence regarded knowledge growth as something that happens continually in a sequential process consisting of logically embedded process consisting of logically embedded structures succeeding one another throughout an individual life time. This is divided into stages of development
1. The sensorimotor stage (18 months to 2 years) 2. The preoperational stage (2 to 7 years) 3. The concrete operational stage (7 to 12 years) 4. The formal operational stage (12 years and above)