Filter was proposed by Dulay and Burt (1977), and is consistent with the theoretical work done in the area of affective variables and second language acquisition, as well as the hypotheses previously covered in this chapter.

Research over the last decade has confirmed that a variety of affective variables relate to success in second language acquisition (reviewed in Krashen, 1981). Most of those studied can be placed into one of these three categories:

In several places I have hypothesized that these attitudinal factors relate directly to acquisition and not learning, since they tend to show stronger relationships to second language achievement when communicative-type tests are used, tests that tap the acquired rather than the learned system, and when the students taking the test have used the language in "acquisition-rich" situations, situations where comprehensible input was plentiful.

The Affective Filter hypothesis captures the relationship between affective variables and the process of second language acquisition by positing that acquirers vary with respect to the strength or level of their Affective Filters. Those whose attitudes are not optimal for second language acquisition will not only tend to seek less input, but they will also have a high or strong Affective Filter--even if they understand the message, the input will not reach the part of the brain responsible for language acquisition, or the language acquisition device. Those with attitudes more conducive to second language acquisition will not only seek and obtain more input, they will also have a lower or weaker filter. They will be more open to the input, and it will strike "deeper" (Stevick, 1976).

The Affective Filter hypothesis, represented in Fig. 2.2, claims that

31