Given a realistically sized task (and assuming that he cannot already perform it), a student is unable to generate the required performance strategy all at once. Instead, he directs his attention to various facets or subtasks and musters subroutines that build up a performance strategy bit by bit. The process is carried out by a learning strategy which, in the free learning subject, may be innate or acquired and which, for the student, is imposed externally by a teacher or learning system.

p. 261. - Conversation, Cognition and Learning (1975)