Lev Vygotsky was a Russian psychologist who developed the sociocultural theory of cognitive development, which emphasizes how social interaction and culture impact cognitive development. He believed that community plays a central role in the process of "making meaning." A key concept is the Zone of Proximal Development, which is a child's potential development when aided by a more knowledgeable other such as a teacher or peer. Vygotsky argued that optimal learning occurs in the Zone of Proximal Development through guided collaboration with others.