Assessing The Contribution Of Vocabulary Breadth And Depth To The Prediction Of L2 Proficiency

Over the last twenty years, vocabulary has been upgraded as a component of language proficiency in both first and second language acquisition research. To figure out the role of vocabulary knowledge in second language (hereafter L2) proficiency, many researchers have made relevant empirical investigations. But their findings reached no agreement on its role. In the hope of helping L2 learners and researchers better understand the role of vocabulary knowledge, this thesis explores the relationship between vocabulary knowledge and the proficiency of English as a second language (hereafter ESL) from the perspective of two primary dimensions of vocabulary knowledge, i.e. breadth and depth.Vocabulary knowledge is believed to be multidimensional and to encompass various aspects of knowledge. As two primary dimensions of this complex system, breadth and depth are taken as the starting point of this thesis. To make a close estimation of the subjects' vocabulary knowledge and L2 level, 83 second-year university students who were non-English majors were supervised to do three language tests: the vocabulary breadth, vocabulary depth, and English proficiency tests. The scores from these three tests were put into computer as the firsthand data and then processed through SPSS 13.0. The results support the following hypotheses: (1) breadth, depth, and L2 comprehensive proficiency are significantly and positively correlated; (2) both vocabulary breadth and depth have a predictive power upon L2 comprehensive proficiency and specific language skills; (3) vocabulary breadth possesses a stronger power as a predictor than depth does; (4) Generally speaking, a significantly positive correlation exists between breadth and depth, but for learners of different levels of breadth this relationship varies.The findings from this empirical study call for more attention to the importance of improving vocabulary knowledge in ESL learning process. L2 learners who would like to improve his/her L2 proficiency will benefit from the expansion of breadth and depth of vocabulary knowledge. As an effective predictor to L2 proficiency, depth of vocabulary knowledge should not be neglected any longer. Thus L2 learners and teachers are strongly recommended to involve vocabulary depth as well as breadth into their learning and teaching. For L2 learners, they are suggested to choose appropriate learning strategies and emphasis in accordance with their situation. And L2 teachers are expected to provide students with a well-balanced language course that systematically incorporates various aspects of vocabulary knowledge.