ABSTRACT
This chapter deals with the nature of evidence available to learners. The focus is on the kinds of evidence that a learner needs in order to construct and revise grammatical knowledge successfully. The chapter also includes a review of some of the pertinent child language literature relating to negative evidence. In particular, if second language learners are to achieve nativelike competence in a second language (a big if), they need to come up with the same sort of knowledge about the abstract structure of the target language as native speakers do, and this information is not available from the input. The situation is, of course, more complex because (adult) L2 learners have access to a fullblown language when they approach the learning of a nonprimary language. The chapter considers forms that might be in competition, for example, an irregular past tense form, such as singed versus sang versus sung.
