A Corpus-based Study Of Developmental Patterns Of Changes In Chinese EFL Learners' Oral Productive Vocabulary

This thesis reports a study whose aim was to attempt to investigate the developmental pattern of changes in the size of productive vocabulary of Chinese EFL learners in their oral composition. Productive vocabulary was measured in the study by two of the theoretically and practically accepted indexes, lexical variation and lexical sophistication, based on an assumption that L2 learners'lexicon grows with the years of learning and that more advanced students can produce more varied and sophisticated vocabulary. Lexical variation was expressed by the Mean Type/Token Ratio; lexical sophistication was represented by the Lexical Frequency Profile and the Condensed Lexical Frequency Profile. To be specific, two research questions were addressed: 1) Does lexical variation of productive vocabulary change over time? If so, what are the developmental patterns of such changes with students of different proficiency levels? 2) Does lexical sophistication of productive vocabulary change over time? If so, what are the developmental patterns of such changes with students of different proficiency levels?Spoken data employed in the study were selected from SECCL, a Chinese learner corpus. Involved in the analysis were 60 oral compositions, 30 of which were produced by Year Two students in a TEM-4 testing context and 30 by Year Four students in a TEM-8 testing context. For the purpose of comparisons, the sampled cases in different testing situations were divided respectively into high- and low-level groups, according to the test-takers'performance. All the selected data were processed by the corpus tools: Wordsmith and Range. Data analysis generated the following major findings:Firstly, there is no significant difference between the second- and fourth-year students in the means on the Mean Type/Token Ratio, which suggests that the Chinese EFL learners do not demonstrate an increase in the use of different words in their oral work with the years of learning. Such an explanation is contrary to the researcher's presumption that L2 learners'lexical variety grows with the years of learning. However, the lack of a difference in lexical variation between the two groups of students may be due to the sensitivity of the measure of lexical variation to text type and content.Secondly, comparisons between the high-level groups in both TEM-4 and TEM-8 testing contexts indicate that there is no significant difference in the use of different words in the learners'oral production. However, it is interesting to note that the low-level groups show a significant difference in lexical variation, and the fourth-year students produce less varied lexicon, implying that the fourth-year students tend to receive less training either because of the smaller proportion of oral courses in the curriculum or because of the challenges that the students have to encounter in job hunting. This explanation may hold true to the lack of difference in lexical variation between the high-level groups.Thirdly, comparisons of the Lexical Frequency Profile show two major developmental patterns in Chinese learners'use of productive vocabulary. On the one hand, there is no significant difference between the second- and fourth-year students'use of the lexical items belong to the 2,000 frequency band and least frequent lexical items, indicating that English majors'lexicon show the similar pattern of sophistication in using most frequent and least frequent words, regardless of differences in learning stages. On the other hand, both the second- and fourth-year students differ in the use of the lexical items belong to the 1,000 and 3,000 frequency bands, from which it can be concluded that the second-year students tend to use significantly more basic words, whereas the fourth-year students tend to use obviously more advanced vocabulary.The above results may be better confirmed by comparisons of the Condensed Lexical Frequency Profile, which indicate that there is a significant difference between the second- and fourth-year students'use of frequent (represented by the above 2,000 level) and infrequent (represented by the below 2,000 level) vocabulary. In addition, comparisons of the Lexical Frequency Profile between both TEM-4 and TEM-8 test takers, either high- or low-level, also show that students of different proficiency levels take on a similar pattern of lexical sophistication, that is, students, along with the increase of learning years, use less words in the first frequency band and more words in the third.Practically, findings in this study have important implications for the research in the field of quantitative description of learners'productive lexical command. Firstly, the exploration into lexical developmental changes may help language instructors to have a better understanding of the quantitative aspect of L2 productive lexical competence in terms of variety and sophistication. Secondly, oral practice should be directed towards use of more frequent words, so that learners'oral work distinguishes itself from written production. To some extent, this study paves the way for future study on productive vocabulary in Chinese EFL learners'spoken production of different type or in different contexts.