Krashen, Stephen D

Krashen is best known for his work in establishing a general theory of second-language acquisition, commonly called the Monitor Theory, as the cofounder (with Tracy Terrell) of the Natural Approach to second-language teaching, and as the inventor of sheltered instruction.

A central element of Krashen's approach to second-language acquisition is the view that it occurs naturally, just like first-language acquisition, under appropriate conditions. This view constituted a dramatic shift from an earlier position in Krashen's published work reflecting a commitment to direct instruction and consistent error correction.

In a seminar in 1975, Krashen and his students sought to make sense of data pertaining to a fixed pattern of acquisition of grammatical morphemes from second-language speakers. During the seminar, Krashen came up with the idea that two systems, an acquired one and a learned one, must be posited to explain the data.

Krashen's general approach to second-language acquisition evolved to include five interrelated hypotheses, including the natural order hypothesis (the idea that human beings acquire the rules of language in a predictable order); the acquisition/ learning hypothesis, which states that adults have two distinctive ways of developing competences in second languages (acquisition—a system that develops from natural language use—and learning—a system that comprises overt knowledge of language rules); the monitor hypothesis (conscious learning can only be used to monitor or edit our language); the input hypothesis (humans acquire language by understanding messages); and the affective filter hypothesis (a mental block, caused by affective factors, prevents input from reaching the language acquisition system in the brain).

Krashen has also contributed extensively to an approach in reading known as Whole Language, which similarly posits that children learn to read by reading and that reading develops naturally under appropriate conditions.

 Source: SAGE REFERENCE ONLINE