Piaget's Stages of Cognitive Development
Jean Piaget's theory of cognitive development describes how children's thinking changes qualitatively at different ages. The Sensorimotor Stage (birth to 2 years): infants learn about the world through their senses and physical actions. The landmark achievement is object permanence — the understanding, typically around 8–12 months, that objects continue to exist even when out of sight. Before this, a hidden toy simply 'doesn't exist' to the infant. The Preoperational Stage (2–7 years): children develop language rapidly and engage in symbolic and imaginative play. However, thinking is still egocentric — the child believes others see and experience the world exactly as they do. They lack conservation — the understanding that quantity stays the same when shape changes (pouring water from a short wide glass into a tall narrow glass looks like 'more' to a 4-year-old). The Concrete Operational Stage (7–11 years): children can think logically about concrete, tangible objects and events. They understand conservation, can classify objects, and understand that operations can be reversed. Abstract reasoning is still limited. The Formal Operational Stage (12+ years): abstract, hypothetical, and deductive reasoning develops. Adolescents can think about ideas, possibilities, and logical consequences they have never directly experienced.