Assessing the Roles of Metacognitive Knowledge and Vocabulary Size in EFL Reading Comprehension

Recent studies show that the influence of metacognitive knowledge on the second language reading increased with the increasing vocabulary knowledge. However, the relationship among metacognitive knowledge, language knowledge and EFL reading still needs to be further clarified. How does vocabulary knowledge make an independent contribution to L2 reading? How does it moderate the effect of metacognitive knowledge on L2 reading? This study assesses the roles of metacognitive knowledge and vocabulary size in EFL academic reading based on Chinese tertiary EFL learners. The participants include 548 non-English major sophomore students in mainland China. The instruments include a questionnaire on the metacognitive knowledge of EFL reading comprehension, Vocabulary Levels Test (Nation, 1990) and an EFL reading comprehension test. The findings reveal that Chinese tertiary EFL readers only approach 3,000-word level. Vocabulary size does not only exert direct influences on EFL reading comprehension ability, but also plays a significant moderating role in regulating the effect of metacognitive knowledge on EFL reading comprehension ability. When the vocabulary size reaches above the threshold of 3,000 words, metacognitive knowledge plays an increasing role in EFL reading comprehension ability. The theoretical and educational contributions of these findings for L2 academic reading are discussed.