Abstract
The present study aims to reexamine Qian's (1999) empirical research, which explored the relationship between depth and breadth of vocabulary knowledge and reading comprehension in English as a second language. Qian assessed the performance of the subjects with a minimum vocabulary size of 3,000 word families in general academic reading comprehension tests, while about two-thirds of the subjects in the present study have not acquired 3,000 word families. The results show, as Qian proved, that scores of vocabulary size, depth of vocabulary knowledge, and reading comprehension are significantly correlated. However, in the multiple regression analysis, this study shows that scores of vocabulary size can make a unique contribution to the prediction of reading comprehension levels, in addition to the prediction given by scores on depth of vocabulary knowledge, in contrast to Qian's results. The findings from this study reveal the importance of increasing both depth and breadth of vocabulary knowledge to improve reading comprehension, and indicate that depth of vocabulary knowledge might increase in importance, as the size of the lexicon gets larger.
