Krashen's theory of second language acquisition
It consists of five main hypotheses: the acquisition-Learning hypothesis, the monitor hypothesis, the natural order hypothesis, the comprehensible input hypothesis, and the affective filter hypothesis.
In developing his theory, Krashen acknowledges "those scholars whose work has stimulated my own thinking in the early stages of the research reported on here: John Upshur, Leonard Newmark, and S. Pit Corder all recognized the reality of language "acquisition" in the adult long before I did".
- Krashen, Stephen D. Principles and Practice in Second Language Acquisition. Prentice-Hall International, 1987.
- Krashen, Stephen D. Second Language Acquisition and Second Language Learning. Prentice-Hall International, 1988. ISBN 0-08-025338-5