EPILOGUE
Lyster and Saito (this issue) in their excellent meta analysis of classroombased oral corrective feedback (CF) studies, comment that "the fi eld of CF research has grown dramatically over the last 20 years" (p. 295) Lyster and Saito are referring to oral CF research, but in fact this growth is evident in both oral and written CF research. In the case of oral CF studies, there has been a progression from predominantly descriptive studies aimed at developing taxonomies of the CF strategies (e.g. Allwright, 1975 Chaudron, 1977 to experimental studies that investigate the effects of different types of CF strategies on second language (L2) development (e.g. Lyster, 2004 Sheen, 2007b In the case of written CF studies, there has been a progression from studies concerned primarily with the effects of CF on learners' revision of their original texts (e.g. Fathman Whalley, 1990 to experimental studies with designs similar to those found in oral CF research that investigate what effect written CF has on the accuracy with which learners use specifi c grammatical structures in new pieces of writing (Bitchener, 2008 Sheen, 2007a Why has the interest in CF been so intense? The answer to this question lies partly in the fact that CF is of both theoretical relevance to SLA researchers and of practical concern to language teachers and partly in the fact that it is a highly researchable phenomenon. The theoretical signifi cance of CF research is perhaps more evident in the case of oral CF studies. SLA theories differ both in the importance attached to CF and in the type of feedback hypothesized needed for acquisition. Thus, whereas theories derived from Chomsky's Universal Grammar (e.g. Schwartz, 1993 claim that acquisition is driven entirely by positive evidence and, thus, that CF has no role as a source of negative
Studies in Second Language Acquisition