Jean PIAGET 09 August 1896 – 16 September 1980
Swiss Psychologist. He constituted the concept of “Developmental Level”. His theory, known as the Piaget Theory, revealed that everyone passes through some unchangeable levels and that everyone is separated from each other as measurable. Piaget has made groundbreaking studies in the field of genetic epistemology, cognitive development and developmental psychology. Piaget showed that the development of thought and language in children are not formed in a continuous way, but through stages and that, it is structured effectively in individual and environment relations.