Lev Semyonovich Vygotsky (Лев Семёнович Вы́готский or Выго́тский, born Лев Симхович Выгодский [Lev Simkhovich Vygodskiy], November 17 [ November 5] 1896 – June 11, 1934) was a Soviet psychologist, the founder of an unfinished theory of human cultural and bio-social development commonly referred to as , the prominent advocate for the new theory of consciousness, the “psychology of superman”, and leader of the (also referred to as ‘Vygotsky-Luria Circle’).:
Vygotsky’s main work was in developmental psychology, and he proposed a theory of the development of “higher psychological functions” that saw human psychological development as emerging through interpersonal connections and actions with the social environment. During the earlierand “instrumental psychology” period of his career (1920s) he argued that human psychological development was mediated by signs that he viewed as psychological equivalent of instrument use in human labor and industry. In the later, the “ ” period of his career (first half of 1930s), Vygotsky got increasingly influenced by the systemic thinking of the scholars associated with German-American movement. It was during this period that he–under the influence of ‘s “ “–introduced the vague notion of the “ ” and identified play of young children as their “leading activity”, that he understood as the main source of the preschoolers’ development in terms of emotional, volitional and cognitive development.