In Vygotskyan sociocultural theory, internalisation is described as:
Reconstruction on the inner, psychological plane, of socially mediated external forms of goal-directed activity.
Any function in the child's cultural development appears twice or on two planes. First it appears on the social plane, and then on the psychological plane. First it appears between people as an interpsychological category, and then within the child as an intrapsychological category.
(Vygotsky, 1981, p.163).