Vygotsky, Lev Semyonovich, 1896–1934, Russian psychologist. His most productive years were at the Institute of Psychology in Moscow (1924–34), where he expanded his ideas on cognitive development, particularly the relationship between language and thinking. His writings emphasized the roles of historical, cultural, and social factors in cognition and argued that language was the most important symbolic tool provided by society. His Thought and Language (1934) is a classic text in psycholinguistics.
See J. V. Wertsch, Vygotsky and the Social Formation of Mind (1985).