The Multidimensional And Dynamic Development Of Lexical Chunks In Second Language Writing

Lexical chunks are a specific kind of multi-word phenomenon,which existed between traditional grammar and vocabulary.They are stored in psychological dictionaries as whole units,reducing the burden on the user’s brain when processing information.They can be automatically identified and retrieved by language users,which contributes to the fluency and authenticity of the language.Previous studies have shown that lexical chunks can be served as a significant indicator of the writing competence of L2 learners.The ability of students to use lexical chunks accurately and appropriately may affect the overall quality of writing texts.Unfortunately,most studies on lexical chunks in second language writing have focused on a group of learners based on a cross-sectional design,and the longitudinal developmental characteristics of individual learners’ lexical chunks are neglected.Additionally,many of them concentrate on the single dimension of lexical chunks.Few studies have examined the dynamic interaction features of L2 learners’ lexical chunk use in multi-dimensions.In view of this,six EFL learners were selected as participants according to the volunteer principle,and we conducted this research over a period of one academic year.Every week they need to complete an English argumentative essay.Eventually,the longitudinal mini-corpus includes 20 times points,and a total of 120 English compositions.Based on the longitudinal design,this study traced the performance of six learners’ lexical chunks from dimensions of fluency,diversity and accuracy.At the same time,a set of Complex Dynamic Systems Theory(CDST)techniques were applied to detect individual variability and interaction features between three dimensions.In addition,a retrospective interview was carried out to identify the factors influencing the development of LCs.This study attempts to answer the following research questions:(1)What are the overall developmental trajectories of six EFL learners in the fluency,diversity,and accuracy of lexical chunks in L2 writing over one academic year?(2)What are the developmental variability characteristics of three dimensions in the process of L2 writing? Is there a significant development?(3)What are the interactive features among fluency,diversity and accuracy of lexical chunks? Competitive or supportive?The results show that(1)L2 learners follow different development trajectories in the three dimensions of lexical chunks,which varied and characterized by non-linearity,unpredictability,and individual difference.(2)When it comes to variability,regularity and difference coexist.Variability analysis presents that individual’s lexical chunks develop non-equally and vary non-synchronously in multiple dimensions.The change-point analyzer detected that H in lexical chunk fluency,Z and W in the lexical diversity,and H in lexical chunk accuracy,achieved stepwise development.Although both Z and W showed significant variation in diversity,they had different bandwidth change patterns and inter-individual difference.The study also suggests that the initial proficiency of the learner could be a major element resulting lexical chunk developmental difference.In addition,retrospective interview analysis exposed that various elements such as learning strategies,learners’ engagement,motivation and the way of writing and thinking may have some impact on the variability of LCs to some degree.(3)The development of each dimension does not occur in separation but connects with other dimensions to jointly form the overall performance of the lexical chunks.The dynamic interplay relationship changes over time,with alternating competition and support,which indicates an unbalanced allocation of cognitive resources for individual learners.This study provides some important information about the mechanisms of L2 learners’ lexical chunks development and provides empirical evidence for CDST,Meanwhile,this thesis highlights the applicability of CDST variability analysis method to L2 writing research,as well as providing important insights for LCs instruction.Eventually,the thesis presents the limitations and offers suggestions for the follow-up research.