A meta-analytic review of comprehension deficits in students with dyslexia

Beyond the established difficulties of individuals with dyslexia in word recognition and spelling, it remains unclear how severe their difficulties in comprehension are. To examine this, we performed a meta-analytic review. A random-effects model analysis of data from 76 studies revealed a large deficit in reading comprehension in individuals with dyslexia compared to their chronological-age (CA) controls (g = 1.43) and a smaller one compared to their reading-level (RL) matched controls (g = 0.64). Individuals with dyslexia also differed significantly from their CA controls in listening comprehension (g = 0.43). Results further showed significant heterogeneity in the effect sizes that was partly explained by orthographic consistency (the deficits were larger in languages with low orthographic consistency) and vocabulary matching (the deficits were larger in studies in which the groups were not matched on vocabulary). These findings suggest, first, that individuals with dyslexia experience significant difficulties in both reading and listening comprehension, but the effect sizes are smaller than those reported in the literature for word reading and spelling. Second, our findings suggest that the deficits in reading comprehension are likely a combination of deficits in both decoding and oral language skills.