Every function in the child's cultural development appears twice: first, on the social level, and later, on the individual level; first, between people (interpsychological) and then inside the child (intrapsychological). This applies equally to voluntary attention, to logical memory, and to the formation of concepts. All the higher functions originate as actual relationships between individuals.
Lev S. VygotskyThe child begins to perceive the world not only through his [or her] eyes but also through his [or her] speech
Lev S. VygotskyHuman learning presupposes a specific social nature and a process by which children grow into the intellectual life of those around them
Lev S. VygotskyChildhood is a complex dialectical process characterized by periodicity, unevenness in the development of different functions, metamorphosis or qualitative transformation of one form into another, intertwining of external and internal factors, and adaptive processes which overcome impediments that the child encounters.
Lev S. Vygotsky