Dr Krashen is one of the world leaders in the fields of bilingual education, neurolinguistics, second language acquisition and literacy. He has authored over 250 articles and books and has received numerous awards.
At one time, it was assumed that the only way of developing grammatical competence in a second language was through direct teaching of grammar. We all held the “skill-building” position: We learn language by first learning the rules consciously, then practicing them in output exercises, and we fine-tune our knowledge of rules by getting our errors corrected.
This axiom has been demoted to the level of hypothesis: It has been argued that we develop competence in second languages in another way. We acquire the grammatical rules of a language by understanding input containing these rules. Our attention is not on consciously learning the rules but on understanding the message, and we subconsciously absorb the rules the same way children absorb the rules of their first language. Conscious knowledge of grammar has a limited function: It is used to edit or monitor our second language production. We can use the conscious grammar to make small grammatical repairs when we have time, when we are thinking about correctness, and when we know the rules. Conscious knowledge is thus not useless, but it has a limited function.
The evidence for the ‘comprehension’ or ‘input’ hypothesis includes studies showing that students in comprehension- based second language classes consistently outperform those in traditional classes, at both the beginning and intermediate levels, and includes studies showing the powerful impact of recreational reading (Krashen, 2003).
There is also strong indirect evidence supporting the comprehension hypothesis. The grammatical system of any language is far too complex to be consciously learned, and many people develop high levels of competence without formal instruction. Quite often, those who have not reached the highest levels of competence in second languages, despite what seems to be a great deal of exposure, have not been readers