In instructional methods combining behaviorist learning principles with a structuralist approach to language such as the Audio-Lingual Method, habit formation was a main concern.
Grammar learning was thought to take place through a process of verbal 'habit formation.' Habits were established through stimulus-response conditioning, which led to the 'overlearning' of the grammatical patterns of a language.
(DeCarrico, J. & Larsen-Freeman, 2002)
Habit formation was defined by contemporary foreign language educators as the "production of linguistics responses to stimuli by imitation and repetition in pattern drill" (Rivers, 2001).
As Bloomfield had it:
Language learning is overlearning; anything less is of no use.
Against charges of anti-intellectualism, Lado defended this approach as useful for creating automatic responses to low-level problems which therefore freed the learner to concentrate on higher issues.