The document summarizes Jean Piaget's theory of cognitive development, which outlines 4 stages: sensory-motor, pre-operational, concrete operational, and formal operational. The sensory-motor stage culminates in symbolic representation and object permanence. In the pre-operational stage, children can use symbols but lack logical operations. They fail conservation tasks and think egocentrically and intuitively rather than logically. This stage reflects a general characteristic in children's thinking at this age.