The stages of cognitive development were introduced by Jean Piaget, a developmental psychologist. They are:Sensorimotor Stage (0–2 years)Child learns through senses and movement.Develops object permanence (knowing things still exist even when out of sight).Preoperational Stage (2–7 years)Learns to use language and symbols.Thinking is egocentric (they can’t see things from others’ perspectives).Imagination is active.Concrete Operational Stage (7–11 years)Begins logical thinking about concrete events.Understands concepts like conservation (amount stays the same even if shape changes).Less egocentric.Formal Operational Stage (12 years and up)Can think abstractly and solve complex problems.Can form hypotheses and think about future possibilities.These stages help us understand how children develop reasoning and understanding.