C/T Number of clauses per T-unit

CAF Complexity, accuracy, and fluency, 

L2 Second language

MSR-D Mean segmental ratio-D

TEM-8 Test for English Majors Band-8

W/C Number of words per clause

W/T Number of words per T-unit 

1 IntroductionFrom+优!尔.YouErw.com 加QQ75201`8766 1。1 Research Background

As one of the five basic skills of second language (L2) learning, writing occupies an important position in language teaching and testing。 Since the 1970s, L2 writing has attracted ever-increasing attention of both foreign and domestic researchers (Bao, 2009; Cooper, 1976; Laufer, 1991; Polio, 1997; Qin & Wen, 2007; Skehan, 2009; Wilkins, 1972)。 Lots of aspects have been studied, such as writing texts, writing process and so on。 Among them, research on writing texts focused on the complexity, accuracy and fluency of writing language, the study of lexical features, writing coherence, etc。 Moreover, language complexity, accuracy, fluency (CAF) can appropriately reflect the performance and the level of the second language learners (Housen & Kuiken, 2009; Skehan, 2009)。 With regard to complexity, some researchers have explored such fields as measurement index (Ortega, 2003; Wolfe-Quintero, Inagaki, & Kim, 1998), language proficiency (Engber, 1995), language development (Hunt, 1965; Larsen-Freeman, 2006; Laufer, 1991), etc。 Recently, language complexity is further distinguished as syntactic complexity and lexical complexity, proposed by Skehan (2009)。 论文网

Compared with foreign studies of language complexity, domestic studies, especially those on syntactic complexity, are significantly scant。 However, researchers have become increasingly interested in this area in recent years。 The domestic research regarding complexity involves fields like measures (Chen, 2015; Zhang, et al。, 2015), developmental trend (Bao, 2009; Ji, 2006; Qin & Wen, 2007), comparisons (Wang, 2009; Wen, et al。, 2003), etc。 But it should be noted that the research of exploring the development of language complexity is still limited in number and scope at home。 

Therefore, the present study was aimed at finding the development of syntactic and lexical complexity of L2 writing of English majors and the differences between the compositions of the participants and some high-scoring compositions from TEM-8 tests。 This research was a further study on my scientific training project on the development of lexical complexity and the result has been published in the journal of Educational Modernization (Li, et al。, 2015)。

1。2 Significance of the Study

This research differed from studies on CAF in L2 writing in the existing literature in a few aspects and therefore has its significance。 

First, the majority of previous CAF studies were conducted in the field of L2 speaking (Wen, 2006; Wen, Ding & Wang, 2003)。 In addition, most of the CAF studies in L2 writing probed into the development of accuracy, syntactic complexity and lexical complexity separately (Bao, 2009; Gan, 2013; Xu, et al。, 2013; Zhang, 2015)。 Fewer studies focused on the developmental features of written texts across different proficiency levels。 The present study not only examined the development of language complexity (syntactic and lexical complexity), but also compared the experimental groups with high-scoring compositions from TEM-8 writing texts in order to find out the differences, portray successful English writers, and help improve the teaching and learning of English writing。 

Second, the present study employed relatively new syntactic and lexical complexity metrics developed by researchers in recent years。 In previous CAF studies in L2 writing research, a great number of complexity, accuracy, and fluency measures are used to evaluate language development of students (see Wolfe-Quintero, Inagaki, and Kim, 1998 for a review)。 However, some of the metrics were criticized by researchers。 For instance, Norris and Ortega (2009) argued, some metrics are redundant and measure exactly the same thing, for example, the family of measures of subordination。 They also argued that the large family of syntactic complexity measures evaluates different syntactic sub-constructs。 For instance, length-based metrics with a multiple-clausal unit of production in the denominator seem to measure overall complexity; metrics with clause in the numerator appear to measure subordination complexity; and mean length of clause measures subclausal or phrasal complexity。 Therefore, syntactic complexity in the present study was pided into the three subcategories suggested by Norris and Ortega (2009)。