A Corpus-based Study Of Lexical Chunks In English Argumentative Essays Of EFL Learners

In recent years, an increasing number of researches have made use of corpus data to emphasize the importance of multi-word sequences in language. The present thesis investigated lexical chunks which are defined as "recurring sequences of three or more words that co-occur frequently in a register"(Biber1999:990). Following Biber et al.’(2004) and Cortes’(2004) taxonomies, a corpus-based approach is taken to the identification of lexical chunks. The present research aims at identifying and elaborating the structures and functions of lexical chunks in argumentative writings by comparing the use of certain lexical chunks in the native speaker corpus (as represented in EDC) and the Chinese EFL learner corpus (as represented in CEM).Lexical chunks retrieved from the two corpora were investigated both quantitatively and qualitatively. The present research indicates that the use of lexical chunks between native speakers and non-native speakers is quite different. Although Chinese learners use more four-word lexical chunks, most of the lexical chunks are topic-related. Firstly, a structural taxonomy is presented, including NP-based chunks, PP-based chunks and VP-based chunks. The results reflect that Chinese learners use more VP-based chunks such as "pronoun+VP fragment" which indicate the speech-like feature in Chinese EFL learner corpus, while native speakers use more NP-based chunks and PP-based chunks. The findings show that native speakers use a great deal of "noun+of-phrases" and "preposition+of-phrases". Then a functional taxonomy is presented, including stance expressions, referential expressions and discourse organizers. Chinese EFL learners use more stance expressions, especially "I think" type, while native speakers use more referential expressions and discourse organizers. However, Chinese EFL learners seem to have recognized the importance of discourse organizers in their written productions. Additionally, some lexical chunks with high frequency in native speaker corpus were underused in Chinese EFL learner corpus, while certain expressions which native speakers rarely used were overused by Chinese EFL learners. The overuse of some certain lexical chunks (e.g. as we all know, on the other hand) which Chinese EFL learners become more familiar with is probably a form of overgeneralization. In addition, when Chinese EFL learners did use certain lexical chunks, their use did not correspond to the use of lexical chunks employed by native speakers.Finally, some pedagogical implications of the findings, as well as future researches are introduced and discussed.