Differences in the components of reading comprehension in developmental dyslexia: A longitudinal and cross-sectional investigation

PURPOSE: The Simple View of Reading proposes that decoding and language comprehension together explain reading comprehension. The current study investigated whether adding rapid automatized naming (RAN) and verbal short-term memory (VSTM) enhances the prediction of reading comprehension, and whether there are differences in the relative contribution of the four components in typical development and in dyslexia, and across development. METHOD: Using data-driven Bayesian model comparison and selection strategies, we investigated the relative contribution of the four component abilities in English-speaking individuals with (Dys) and without (Typ) dyslexia, including first to second graders (N = 149; mean age 7.21to 8.25 years; 34 Dys: 16 female, 18 male; 115 Typ: 56 female, 59 male), third and fourth graders (N = 80; mean age 9.54 years; 48 Dys: 25 female, 23 male; 32 Typ: 9 female, 23 male), and adults (N = 60; mean age 26.31 years; 28 Dys: 17 female, 11 male; 32 Typ: 15 female, 17 male).RESULTS: For typical readers, the importance of decoding decreased over development, while language comprehension increased; RAN and VSTM had no additional predictive value. In dyslexic readers, decoding was the primary predictor in children across grades (with small contributions from RAN and language comprehension) and VSTM was the primary predictor in adults. CONCLUSIONS: These findings underscore that variations in decoding skills significantly constrain reading comprehension in dyslexia, limiting comprehension due to inaccurate reading in childhood and creating a cognitive bottleneck in adulthood.