Stephen Krashen is an emeritus professor of education at the University of Southern California. His research concerns second language acquisition (SLA), bilingual education, literacy and neurolinguistics. His work seeks to inform policy on bilingual education and reading instruction, being supportive of the whole language reading methodology. In SLA and applied linguistics his "five hypotheses" about language acquisition, collectively known as monitor theory, remain influential in both theoretical linguistics and language teaching, and he also developed the comprehension-based natural approach to second language learning with Tracy D. Terrell.
Monitor theory states that adult learners have two systems to enable them to develop their language ability: subconscious acquisition and conscious learning, with acquisition being more important. Conscious learning is only available as a "monitor", i.e. learners can consciously 'edit' their 'output' (utterances or written work) to make themselves more fluent or comprehensible, based on what they have formally learned about the second language (e.g. through a focus on grammar in the classroom). This, however, has no effect on subconscious, true acquisition, and in its absence, output will be less 'accurate' or native speaker-like. The model has been strongly criticised due to the prevailing mood in applied linguistics that learned knowledge does form part of true acquisition, though many of its conclusions are shared, directly or indirectly, by theoretical linguists and teachers.
- Krashen (1996).
- e.g. Krashen (1999).
- Krashen rarely uses the term monitor theory term in his books. He does refer to them as one theory, however, e.g. Krashen & Terrell (1983: 26), and in academic discussion he has explicitly used the term monitor theory to mean the five hypotheses, e.g. Krashen (1981b: 219-220).
- Krashen & Terrell (1983).
- Krashen (1981a: 1-2).
- See e.g. Young-Scholten (1999) for a theoretical perspective. See e.g. Scrivener (2005:19), a handbook for teachers, which points out that the alternative of a strong focus on explicit instruction has proved of little help to beginning learners. See Gregg (1984) for a strong critique of Krashen's hypotheses.