Modeling phonological core deficits within a working memory architecture in children and adults with developmental dyslexia

Recent theoretical advances in working memory guided analyses of cognitive measures in 122 children with dyslexia and their 200 affected biological parents in families with a multigenerational history of dyslexia. Both children and adults were most severely impaired, on average, in three working memory components-phonological word-form storage, time-sensitive phonological loop, and executive functions involving phonology. Structural equation modeling showed that, for children, first-order factors from the phonological, orthographic, and/or morphological word forms uniquely predicted 11 reading and writing outcomes but, for adults, a second-order factor (reflecting interrelationships among the three first-order word-form factors) was more likely to be significant in predicting the same reading and writing outcomes. Structural equation modeling of the three working memory component factors showed that the most consistent predictor of text-level reading and writing for both children and adults was the second-order word-form factor. Phonological loop and executive support could be modeled as separate factors in children but only as combined factors in adults. Executive support in children and combined phonological loop and executive support in adults contributed uniquely to oral reading but did not contribute uniquely to reading comprehension or written expression. For both children and adults, individual differences occurred as to which of the three working memory components or three word forms fell outside the normal range.