As a result,
the only value of formal instruction is in helping to develop explicit knowledge, which is seen by Krashen as having very limited use, for the purposes of monitoring, and then only when the learner has time to monitor her output. Prabhu’s views are a little different: it is not so much that formal instruction cannot promote the learning of grammar, but rather that grammar is learnt more effectively through communication. Though Krashen’s position has been challenged
by many writers, among them McLaughlin (1987) and Gregg (1984), his ideas and those of Prabhu have nevertheless had a profound influence on language
teaching and helped to destabilise perceptions of the role of form-focused
instruction.