2。1。1　   Definition of Syntactic Complexity 5

2。1。2　   Measures of Syntactic Complexity 6

2。1。3　   Previous Studies on Syntactic Complexity 9

2。1。4　   Summary 10

2。2 Lexical Complexity 11

2。2。1　   Definition of Lexical Complexity 11

2。2。2　   Measures of Lexical Complexity 11

2。2。3　   Previous Studies on Lexical Complexity 13

2。2。4    Summary 14

3 Research Methodology 15

3。1 Research Questions 15

3。2 Participants 15

3。3 Instruments 15

3。4 Data Collection 16

3。5 Data Analysis 16

3。6 Effect Size Calculation 17

4 Results and Discussion 18

4。1 Results for Syntactic Complexity 18

4。2 Discussion for Syntactic Complexity 21

4。3 Results for Lexicial Complexity 22

4。4 Discussion for Lexicial Complexity 24

Conclusion 26

Acknowledgements 28

References 29

Appendix A　Writing Prompts 32

Appendix B　Guidelines for T-units and Clauses 33

List of Tables and Figures

Table 2。1　Syntactic complexity measures adopted in the study 9

Table 2。2　Lexical complexity measures adopted in the study 13

Table 4。1　Mean numbers of words, clauses, T-units, W/T, C/T, and W/C 18

Table 4。2　Results of one-way ANOVA on syntactic complexity 19

Table 4。3　Results of multiple comparisons on syntactic complexity 19

Table 4。4　Results of Mann-Whitney Tests on syntactic complexity 20

Table 4。5　Results of one-way ANOVA on lexical complexity 23

Table 4。6　Results of Mann-Whitney Tests on lexical complexity 23

Figure 4。1　Development of syntactic complexity 21

Figure 4。2　Development of lexical complexity 24

List of Abbreviations

AWL Academic word list 英语专业学生议论文写作句法和词汇复杂性发展趋势研究(2):http://www.youerw.com/yingyu/lunwen_145251.html