Thirty-one 8-and 9-year-old children selected for dyscalculia, reading difficulties or both, were compared to controls on a range of basic number processing tasks. Children with dyscalculia only had impaired performance on the tasks despite high-average performance on tests of IQ, vocabulary and working memory tasks. Children with reading disability were mildly impaired only on tasks that involved articulation, while children with both disorders showed a pattern of numerical disability similar to that of the dyscalculic group, with no special features consequent on their reading or language deficits. We conclude that dyscalculia is the result of specific disabilities in basic numerical processing, rather than the consequence of deficits in other cognitive abilities. q 2004 Published by Elsevier B.V.

In a longitudinal study, development of word reading fluency and spelling were followed for almost 8 years. In a group of 115 students (65 girls, 50 boys) acquiring the phonologically transparent German orthography, prediction measures (letter knowledge, phonological short-term memory, phonological awareness, rapid automatized naming, and nonverbal IQ) were assessed at the beginning of Grade 1; reading fluency and spelling were tested at the end of Grade 1 as well as in Grades 4 and 8. Reading accuracy was close to ceiling in all reading assessments, such that reading fluency was not heavily influenced by differences in reading accuracy. High stability was observed for word reading fluency development. Of the dysfluent readers in Grade 1, 70% were still poor readers in Grade 8. For spelling, children who at the end of Grade 1 still had problems translating spoken words into phonologically plausible letter sequences developed problems with orthographic spelling later on. The strongest specific predictors were rapid automatized naming for reading fluency and phonological awareness for spelling. Word recognition speed was a relevant and highly stable indicator of reading skills and the only indicator that discriminated reading skill levels in consistent orthographies. Its long-term development was more strongly influenced by early naming speed than by phonological awareness.

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14Centre référent pour le diagnostic des troubles du langage et des apprentissages, Département de pédiatrie, CHU Nord, Grenoble, France; Background: The relationship between phoneme awareness, rapid automatized naming (RAN), verbal short-term/working memory (ST/WM) and diagnostic category is investigated in control and dyslexic children, and the extent to which this depends on orthographic complexity. Methods: General cognitive, phonological and literacy skills were tested in 1,138 control and 1,114 dyslexic children speaking six different languages spanning a large range of orthographic complexity (Finnish, Hungarian, German, Dutch, French, English). Results: Phoneme deletion and RAN were strong concurrent predictors of developmental dyslexia, while verbal ST/WM and general verbal abilities played a comparatively minor role. In logistic regression models, more participants were classified correctly when orthography was more complex. The impact of phoneme deletion and RAN-digits was stronger in complex than in less complex orthographies. Conclusions: Findings are largely consistent with the literature on predictors of dyslexia and literacy skills, while uniquely demonstrating how orthographic complexity exacerbates some symptoms of dyslexia.

In 2 large longitudinal studies, we selected 3 subgroups of German-speaking children (phonological awareness deficit, naming-speed deficit, double deficit) at the beginning of school and assessed reading and spelling performance about 3 years later. Quite different from findings with English-speaking children, phonological awareness deficits did not affect phonological coding in word recognition but did affect orthographic spelling and foreign-word reading. Naming-speed deficits did affect reading fluency, orthographic spelling, and foreign-word reading. Apparently, in the context of a regular orthography and a synthetic phonics teaching approach, early phases of literacy acquisition (particularly the acquisition of phonological coding) are less affected by early phonological awareness deficits than are later phases that depend on the build up of orthographic memory. The double-deficit hypothesis was developed by Maryanne Wolf and Patricia Bowers as an extension of the dominant phonological-deficit explanation of developmental dyslexia (e.g., Bowers & Wolf, 1993; Wolf & Bowers, 1999). The phonologicaldeficit hypothesis postulates an early difficulty in acquiring phonological awareness, which interferes with the acquisition of grapheme-phoneme coding as a word recognition mechanism, which in turn results in reduced self-teaching of orthographic word representations (Share, 1995). The early problem with phonological awareness is seen as resulting from less sharp phoneme boundaries in speech perception (Fowler, 1991) or from less distinct phonological word representations (Elbro & Peterson, 1998). The double-deficit hypothesis acknowledges the phonological awareness deficit of dyslexic children but stresses a deficit in naming speed as a second and equally important cause of reading difficulties. The first demonstration that dyslexic children show impaired naming speed was provided by Denckla and Rudel (1976), whose Rapid Automatized Naming (RAN) Test became the standard assessment of naming speed. In the RAN test, a large array of repeatedly presented, well-known visual patterns (pictured objects, color patches, digits) has to be named as quickly as possible. Wolf, Bally, and Morris (1986) were the In:st to show that early differences in rapid naming are predictive of later reading difficulties. The double-deficit hypothesis is based on findings (reviewed by Wolf & Bowers, 1999) showing that, typically, there are only modest correlations between phonological awareness measures and RAN performance in groups of dyslexic children and that dyslexic children as a group exhibit both phonological awareness deficits and naming-speed deficits. From these findings,

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Comorbidities of learning disorders are not artificial. They are the result of a complex interplay between both general and disorder-specific aetiological factors.

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