Piagetian theory
the theory proposed by Jean Piaget that a child’s cognitive development occurs in four major stages. In the sensorimotor stage (roughly 0–2 years of age), the child develops from a newborn capable only of basic reflexes (e.g., sucking, eye movements) to an infant with increasingly complex repetitive behavior (circular reaction) that eventually becomes goal directed; between 8 and 18 months of age, the child gradually develops the ability to recognize object permanence, and at around 18 months, the child begins to engage in problem solving and other forms of mental combination. During the preoperational stage (roughly 2–7 years), the child is both egocentric, showing little awareness of the perspective of others, and single-minded (see centration); language and rudimentary number-system abilities develop as the child becomes able to understand symbols and to represent experience
symbolically through speech, movement, or other means (see symbolic function). The concrete operational stage (roughly 7–12 years) is characterized by the development of more logically and conceptually based thinking and by a move away from egocentrism toward a decentered understanding of others’ perceptions and of multiple aspects of a problem or situation (see decentration); children in this stage become capable of such mental operations as reversibility, categorization, and conservation. Finally, in the formal operational stage (roughly 12 years and beyond), abstract logical reasoning (i.e., hypothetico-deductive reasoning) and moral reasoning develop. According to this theory, each stage builds on the preceding one. Piaget held that although the age of onset for each stage might vary because of cultural and historical factors, the order of the stages
(décalage) is the same for all cultures. He did not believe it was feasible to hurry children through the unfolding of these stages. Passage through them is facilitated by a balance of two processes: assimilation, in which new information is incorporated into an already existing cognitive structure (schema or scheme); and accommodation, in which already existing structures are changed to accommodate new information. Piaget also proposed a stage theory of moral development (see autonomous stage; heteronomous stage; premoral stage).