Cognitive development refers to the formation of progressively detailed mind maps inclusive of self-regulation, recollection, perception, language skills, problem-solving, and decision-making. This usually occurs from childhood to the teenage years and all the way to full maturity.

Swiss psychologist Jean Piaget created one of the most popular theories ofcognitive development．他认为，儿童的认知发展分为四个阶段。它们分别是感觉运动阶段、前运算阶段、具体运算阶段和形式运算阶段。

During the sensorimotor stage (birth to 2 years), infants and toddlers know their surroundings through their sensations, movements, and basic actions like grasping, sucking, listening, and looking. They also learn about object permanence. This refers to the existence of things even when one can’t see them. As infants begin crawling, walking, and standing, they start interacting with their surroundings to discover how the world functions. As they reach the end of the sensorimotor stage (which is 18 to 24 months), the infants achieve another important cognitive development milestone, namely early language development.

At the preoperational stage (2-7 years), children begin to think about things symbolically. Such thoughts are mainly based on intuition and not entirely driven by logic. They also develop imagination and memory. The emergence of language is another focal point of this stage.

Theconcrete operationalstage (7-11 years) is when elementary-age and preadolescent children start displaying concrete, logical reasoning. However, most children will still be unable to think hypothetically or abstractly. But they’ll become less self-centric and more aware of external events. They’ll also start realizing that their feelings and thoughts are unique and may not be shared by others.

At theformal operationalstage (11+ years), adolescents will start thinking abstractly and hypothetically. They become capable of using symbols related to abstract concepts, such as science and algebra. They can even use reasoning or deductive logic to arrive at specific information from a general principle. With their systematic chain of thoughts, teens can come up with theories and mull over possibilities. They even start thinking about moral, ethical, philosophical, social, and political concepts and matters that need abstract and theoretical reasoning.

Though Piaget emphasized lifelong intellectual growth, he claimed the formal operational stage to be the final phase of cognitive development. His theory of cognitive development has significantly influenced education and parenting. However, some experts disagree with Piaget’s four stages of cognitive development as they consider development to be a continuous process.