Chapter 1 Introduction
1.1 Research Background
English writing is a complex process, which requires English learners to make fulluse of skills they have acquired. The improvement of written English depends on notonly writing practices but also the effectiveness of instruction received. In other words，writing is a rather difficult skill for cultivation compared with other basic skills ofEnglish. However, writing has a facilitative role in second language development (SLD).With slow pace, permanent record and requirement for high degree of precision, writingmakes a contribution to cognitive process and interactive actions which are proved to bebeneficial for second language acquisition (SLA) (Williams, 2012).Complexity, accuracy and fluency are indices to measure the quality of writtenproduction. Researchers have implemented numerous investigations to explore changesin language learners' writing. However, from the perspective of traditional research，second language (L2) learning has been thought of as a static, independent and linearprocess. Researchers are inclined to focus on variations between L2 individuals withoutconsideration of fluctuations within them. As a matter of fact, L2 learning is a dynamicprocess involving numbers of subsystems interacting with each other (Verspoor, Lowie，& Van Dijk, 2008). Dynamic System Theory (DST) reveals characteristics of languagesystem. It explains that changes take place in language system constantly. It stresses thatthese changes taking place in language are closely related to learners themselves and thesocial environment they are in.
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1.2 Purpose and Significance of the Research
Larsen-Freeman (1997) invoked DST in order to view language development as achanging, variable md associate process. Linguistic accuracy and complexity in writtenproduction of L2 learners change at any time. As it is explained in DST, variations inlanguage learning is impacted by internal factors covering learners' languagecompetence, time for study, motivation and learning strategy; it is also relevant toexternal factors including learning environment and effective feedback. All the elementsinteract togetfier to promote the development ofL2 writing (De Bot, Lowie, & Verspoor,2007),It is of great importance to investigate the L2 writing process with consideration ofdifferences both between and within individuals in a dynamic view. To knowdevelopmental characteristics of linguistic accuracy and complexity in written Englishis beneficial for learners and teachers in future study and teaching. For learners, theywould have a clear picture of writing progress and regression. For teachers, they canmake distinguished instructions according to dynamic characteristics of compositionsconcerning linguistic accuracy and complexity of students at different proficiency levels.They can also learn the effectiveness of a pedagogical metfiod on different learners in acertain period through the dynamic assessment of students' essays and adjust teachingstrategies accordingly.
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Chapter 2 Literature Review
2.1 Introduction of DST in SLA
The main purpose of SLA research is to investigate the potential knowledge of L2learners. A framework for previous SLA researches is made by Ellis (2013) coveringseven areas: learner language，leamer-extemal factors, psycholinguistic process,inter-leamer variability, the brain and L2 acquisition, inside the black box of theclassroom, and direct intervention in interlanguage development.According to Ellis (2013), SLA can be divided into two types; General SLA andInstructed SLA. General SLA aims to investigate all L2 learners no matter what settingsthey are in. On the contrary. Instructed SLA focuses on how L2 learners complete L2acquisition in the classroom. With regard to General SLA, it is necessary to distinct“description” and "explanation". The former emphasizes how to identify the propertiesof learner language. The latter shifts point to the explanation of SLA and individualdifferences between learners in a theoretical way. Instructed SLA is concerned with twoaspects including the impact brought by interaction in the classroom and the amount ofknowledge gained by learners in the learning process. “Description” aims to explore theregularities and systematicities in the development of learners. In the term of“explanation”，it is targeted at the reason why learners are capable of acquiring L2knowledge with input that they have access to. Additionally，it is also worth looking intohow L2 learners deal with knowledge in communication and what affect the variation ofeach learner's progress to the completion of the task.
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2.2 L2 Writing and DST
Writing has been reckoned as a kind of output of acquisition traditionally, ratherthan as a facilitating factor in the development of L2. Researches in the preceding daysfound that writing should be the last skill for L2 learners to leam (Hyland, 2011). Onlywhen SLD maintains steady and smooth can writing be taught. However, recently,researchers propose that writing is a facilitating activity for the process of L2 learning.From the perspective of writing-to-leam (Harklau，2002; Manchon, 2009)，there existsome unique elements that may promote SLD. SLD can be divided into three phases onmacro-sense (Housen & Pierrard，2005) including knowledge internalization,knowledge modification and knowledge consolidation. Numerous studies have shownthat output has a great impact on the processes mentioned above (Fortune, 2005; Izumi& Bigelow, 2000; Lapkin，Swain, & Smith，2002; Swain，1998，2000). In terms ofnoticing and input processing in the initial point, learners attempt to use new forms inthe new context as they acquire more L2 knowledge. Meanwhile, the forms they arefamiliar with may also come into being in the context. With their on-going trying out new complex expressions and old ones，they may retrieve and process deeply toincrease the fluency in their use of L2 knowledge. Written records of writers pushthemselves to leam more language forms and expressions in different contexts with timegoing by. Under the writing condition, learners take full use of knowledge specificallythe explicit knowledge they have acquired and take it into their own process of SLA. Insummary, writing promotes language acquisition by encouraging the cognitiveprocesses and interactive moves. Learners' requirement and eagerness for languageprecision in writing encourage them to review their acquired knowledge. Writing, as anoutput of language acquisition，reversely facilitates L2 learning (Williams, 2012).
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Chapter 3 Research Methodology....... 15
3.1 Research Questions....... 15
3.2 Participants....... 15
3.3 Instruments....... 16
3.3.1 Origin .......16
3.3.2 AntConc.......17
3.3.3 Interview....... 17
3.4 Data Collection Procedures .......18
Chapter 4 Results and Discussion....... 20
4.1 Measures of Linguistic Accuracy and Complexity .......20
4.2 Results .......22
Chapter 5 Conclusion....... 49
5.1 Major Findings....... 49
5.2 Pedagogical Implications....... 51
5.3 Limitations and Suggestions....... 52
Chapter 4 Results and Discussion
4.1 Measures of Linguistic Accuracy and Complexity
When researchers measure accuracy and complexity, they are measuring theobservable outcome of representation and restructuring (Bygate, 1999; Ellis, 2002;Larsen-Freeman, 2006; Norris & Ortega，2009; Skehan & Foster, 1997; Wigglesworth& Foster, 2008). Accuracy is described as error-free production. According toWolfe-Quintero (1998)，the accuracy measures for short-term change and holisticjudgment are error-free T-unit per T-unit (EFT/T) and error per T-unit (E/T). It is widelyused for comparison between learners. Complexity means the use of varied andsophisticated structures and vocabulary. Grammatical complexity is measured with theclauses per T-unit (C/T) and dependent clauses per clauses (DC/C). Type-token ratio(TTR) is frequently used to evaluate vocabulary variation.In the present study, lexical errors are divided into four categories: the first onerefers to the confusion of synforms, which means words with similar forms (Laufer,1988). For example, “quite” may be misused instead of “quiet” because of their similarspelling. The second category is misselection. L2 learners may take “benefit” to express"advantage or improvement" wrongly substituting for “beneficial” without consideringthe part of speech. The third category covers the collocation mistakes. L2 learners areinclined to transfer LI into target language while they are completing an English writingtask. For instance, Participant Dai created "perform a discussion" under the impact ofChinese expression “进斤于讨论”.The last one is misformation errors including omissionlike “interesting，，(interesting); misselection like “delitious (delicious)" and misorderinglike "dilecate (delicate)".
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Conclusion
This study closely examined three Chinese EFL learners of different proficiencylevels to identify how the linguistic accuracy and complexity change in respect ofvocabulary and grammar in written English. Results and analyses discussed aboveindicate the following conclusions:Firstly, linguistic accuracy and complexity of EFL learners at different proficiencylevels develop in a nonlinear and dynamic way. Variations of linguistic accuracy andcomplexity within and between individuals take place at any time.As for the learner at the low proficiency level, vocabulary accuracy presents asalient change. It increases smoothly at the beginning but decreases successively in thefollowing essays. It arrives at the bottom in the argumentative essay entitled “ShouldUniversity Campus Be open to Tourists” and peaks at an expository writing task entitled“Changes in the Ownership of Houses”. With reference to grammatical accuracy, itvaries unevenly through the whole study. It ascends moderately in the previous sevenessays while it drops sharply in the following ones.
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Reference (omitted)