Assessing the roles of depth and breadth of vocabulary knowledge in reading comprehension

This empirical study explored the relationships between depth and breadth of vocabulary knowledge and reading comprehension in English as a second language (ESL). Using multivariate analyses, the study examined the roles of depth and breadth of vocabulary knowledge in assessing the performance of a group of young adult ESL learners with a minimum vocabulary size of 3,000 word families in carrying out general academic reading comprehension tasks. The results support the hypotheses that (1) scores on vocabulary size, depth of vocabulary knowledge, and reading comprehension are highly, and positively, correlated; and (2) scores on depth of vocabulary knowledge can make a unique contribution to the prediction of reading comprehension levels, in addition to the prediction afforded by vocabulary size scores. The findings from this study call for a recognition of the importance of improving depth of vocabulary knowledge in learners' ESL learning processes.