Cognitive development refers to the changes in thinking, reasoning, and understanding as a child grows. According to Piaget, cognitive development occurs in distinct stages, each characterised by a different way of thinking and is age-related.

During infancy (sensorimotor stage), the child experiences the world through senses and actions. Initially, the child lacks object permanence—the awareness that objects continue to exist when not perceived. By the end of this stage, the child gradually recognises the permanence of objects.

In early childhood (preoperational stage), the child gains the ability to mentally represent objects that are not physically present. However, thinking shows deficiencies such as centration, irreversibility, and egocentrism. The child can use mental symbols but cannot perform mental operations.

During childhood, increasing brain maturation and experiences contribute to the development of cognitive abilities. Children can perform tasks independently, set goals, and begin to acquire concepts of good and bad, developing a sense of morality.

In adolescence, formal operational thought emerges. Thinking becomes more abstract, logical, and idealistic. Adolescents can think beyond concrete experiences, examine their own and others' thoughts, and compare themselves to ideal standards, achieving a new level of cognitive and social awareness.