Towards a new classification of input: An empirical study of the effect of recasts, negative evidence, and enhanced salience on L2 development

Two interrelated problems which are of crucial importance in second language acquisition theory and research are: (a) determining which types of linguistic input are utilized in the language acquisition process, and (b) investigating the ways in which participation in communicative interaction can promote language development. Recasts (i.e., targetlike reformulations of nontargetlike utterances) have figured prominently in both lines of research, with recent studies documenting significant advantages for learners exposed to this feedback type. While some researchers have maintained that such findings suggest a role for negative evidence (i.e., information regarding the impossibility of certain utterances in the language being learned), this important issue has not been explored directly, as multiple variables are conflated in recasts. Specifically, recasts not only offer implicit negative evidence, but they also provide positive evidence. Moreover, recasts constitute a discourse structure which may enhance the salience of this positive evidence. To date, there is no empirical evidence regarding how recasts promote language development, nor regarding the isolated effects of negative evidence and enhanced salience of positive evidence in oral input.; In order to promote the design of studies which isolate independent features of feedback and input types, this dissertation argues for a new input classification scheme, one in which positive and negative evidence are considered as independent, rather than mutually exclusive, categories. The proposed classification, which includes multiple theoretically-motivated features used to further describe input, is then used in the design of an empirical study in which negative evidence and enhanced salience of positive evidence are isolated.; Seventy-three learners of L2 Spanish engaged in individual communicative interaction with the researcher in one of the following conditions: (a) recasts (i.e., negative evidence and enhanced salience of positive evidence), (b) negative evidence, (c) enhanced salience of positive evidence, (d) unenhanced positive evidence (control). The fact that only the recast and enhanced salience groups performed significantly better than the control group on the posttest and delayed posttest suggests that the utility of recasts derives at least in part from enhanced salience of positive evidence, and that the implicit negative evidence they provide is not a crucial factor.