Lev Vygotsky was a Soviet psychologist born in 1896 who studied child development and education. He is known for his theories of social development and the Zone of Proximal Development. Vygotsky believed that social interaction and culture strongly influence cognitive development in children. He studied how language and thought develop in relation to social and cultural factors. His theory of the Zone of Proximal Development examines the difference between what a child can do independently and what they can achieve with guidance and is used to determine a student's readiness to learn new skills.