Contribution of different aspects of vocabulary depth knowledge to reading comprehension in advanced English L2 readers

Few studies aimed to disentangle different aspects of vocabulary depth (VD) knowledge and examine their contribution to second-language (L2) reading comprehension. To fill this gap, this study distinguished between two VD aspects, that is, semantic network knowledge and polysemous knowledge; and tested how they, together with vocabulary size (VS), predicted reading comprehension in advanced English L2 readers who were international students at UK universities. Hierarchical regression analysis revealed that both VD aspects were a significant, unique predictor of reading comprehension, while VS was the dominant predictor. Differential patterns, however, were revealed when VD and VS were regressed on different reading comprehension tasks. For the “banked cloze” and “sentence matching” tasks, while VS remained as a dominant predictor, the unique effect of neither VD aspect was significant. In contrast, for the “passage comprehension” task, all three VS and VD measures were significant, unique predictors, showing a relatively balanced contribution to reading comprehension. The two VD aspects collectively demonstrated a stronger effect on reading comprehension than did vocabulary size. These findings underscored the importance of VD in L2 reading comprehension and also suggested that L2 readers may utilize their lexical repertoire differentially to cope with varied task demands and comprehension needs.