For example, he outlines four stages of cognitive development:
These four stages have the following characteristics:
Piaget's theory supposes that people develop schemas (conceptual models) by either assimilating or accommodating new information. These concepts can be explained as fitting information in to existing schemas, and altering existing schemas in order to accommodate new information, respectively.
Although some of Piaget's ideas are similar to those of Lev Vygotsky, Piaget was apparently unaware of Vygotsky's work.
Piaget's theories of psychological development have proved influential. Among others, the philosopher and social theorist[?] Jurgen Habermas has incorporated them into his work, most notably in The Theory of Communicative Action[?].