One pervasive limitation of children's reasoning during the preoperational period is egocentrism, the inability to take the perspective of another person. A child may assume that everyone has the same knowledge, experiences, and perspective that he or she has. Concrete Operational Reasoning The concrete operational stage lasts from about age 7 to 11. Now children are able to engage in mental representation and can think logically about the world around them. Specifically, children are able to manipulate their mental representations to think and solve problems.
Thought becomes logical, overcoming the limitations of the preoperational stage of reasoning.
Formal Operational Reasoning During early adolescence, individuals enter Piaget's period of formal operations. Now cognitive development reaches its peak. Teenagers become capable of using and manipulating their symbolic representations in abstract thought. They can create and logically think through hypothetical situations. Scientific and deductive reasoning become possible.