Effects of verbal working memory and cumulative linguistic knowledge on reading comprehension

In the present study, the effects of verbal working memory (VWM) and cumulative linguistic knowledge (CLK) on reading comprehension were investigated using an individual difference approach. We examined whether VWM and CLK are distinct verbal factors and whether each has independent influences on reading comprehension. VWM was tested using the Japanese Reading Span Test (RST). CLK was assessed using information, vocabulary, and similarity subtests of the Wechsler Adult Intelligence Scale-Revised (WAIS-R), as well as with the Hyakurakan kanji reading test. The differences between VWM and CLK were examined using correlation analyses between reading comprehension scores, and digit forward and backward span scores. The results showed that VWM and CLK were independent of each other, and that VWM and CLK independently contributed to reading comprehension. The obtained correlations also showed that CLK was independent of any type of short-term memory, and that the VWM measured using the RST had little correlation with digit span.