Piaget and 4 stages of development

Piaget proposed cognitive development to explain children's errors. This he developed as a result of observing how children develop their ideas. Piaget proposed four cognitive stages. The first being the sensorimotor stage( birth to age two) ex.) touching, looking, hearing. Next was the preoperational stage(age 2-7) The children become egocentric, only seeingthings from their own persepective, not thinking others see things differently. Following this was the Concrete operations stage(age 7-12)children now understand cause, effect, and conservation. And lastly the formal operations stage (from age 12-adulthood.) I believe that even children inthe concrete operation statge can understand and classify ideas, and compare. All of these stages are equally inporrtant hand in hand.