The Role of L2 Vocabulary Knowledge in Writing Proficiency from the Perspective of Mediating Effect of Fluency

The current study aims to probe the effectiveness and predictability of four aspects of lexical knowledge in writing proficiency of 312 Chinese university students of English as an ESL/EFL by pathways analysis of structure equation modeling. Furthermore, Bootstrapping and Monte Carlo statistical methods were used to analyze the mediation role of vocabulary fluency in the relationship between lexicons and writing proficiency. The results indicated that (a) the tested four aspects of lexicon knowledge (receptive/productive vocabulary breadth/depth) were all found to have a potential effect on writing; however, the effect of productive lexicons on writing proficiency is higher than that of receptive ones, and the effect of depth is better than that of breadth in both reception and production; (b) regression analysis demonstrated that overall lexical knowledge can account for 50 percent of the variance in writing; (c) vocabulary fluency plays a partial mediation role between vocabulary knowledge and writing ability; and (d) given the mediation role of lexicon fluency, the regression coefficient of both receptive vocabulary breadth and receptive vocabulary depth raised by 3 percent respectively; however, the regression coefficient of productive vocabulary has no changes. These findings suggest that vocabulary fluency can help language learners perform better in writing ability if only they have high vocabulary levels, especially productive vocabulary knowledge.