Biomedical subjects

Sylviane Valdois

Publications and source records attributed to Sylviane Valdois.

4 recordsLinked to original sources

PubMed2006

Developmental dyslexia: the visual attention span deficit hypothesis.

The visual attention (VA) span is defined as the amount of distinct visual elements which can be processed in parallel in a multi-element array. Both recent empirical data and theoretical accounts suggest that a VA span deficit might contribute to developmental dyslexia, independently of a phonological disorder. In this study, this hypothesis was assessed in two large samples of French and British dyslexic children whose performance was compared to that of chronological-age matched control children. Results of the French study show that the VA span capacities account for a substantial amount of unique variance in reading, as do phonological skills. The British study replicates this finding and further reveals that the contribution of the VA span to reading performance remains even after controlling IQ, verbal fluency, vocabulary and single letter identification skills, in addition to phoneme awareness. In both studies, most dyslexic children exhibit a selective phonological or VA span disorder. Overall, these findings support a multi-factorial view of developmental dyslexia. In many cases, developmental reading disorders do not seem to be due to phonological disorders. We propose that a VA span deficit is a likely alternative underlying cognitive deficit in dyslexia.

Adolescent↗

PubMed2004

The cognitive deficits responsible for developmental dyslexia: review of evidence for a selective visual attentional disorder.

There is strong converging evidence suggesting that developmental dyslexia stems from a phonological processing deficit. However, this hypothesis has been challenged by the widely admitted heterogeneity of the dyslexic population, and by several reports of dyslexic individuals with no apparent phonological deficit. In this paper, we discuss the hypothesis that a phonological deficit may not be the only core deficit in developmental dyslexia and critically examine several alternative proposals. To establish that a given cognitive deficit is causally related to dyslexia, at least two conditions need to be fulfilled. First, the hypothesized deficit needs to be associated with developmental dyslexia independently of additional phonological deficits. Second, the hypothesized deficit must predict reading ability, on both empirical and theoretical grounds. While most current hypotheses fail to fulfil these criteria, we argue that the visual attentional deficit hypothesis does. Recent studies providing evidence for the independence of phonological and visual attentional deficits in developmental dyslexia are reviewed together with empirical data showing that phonological and visual attentional processing skills contribute independently to reading performance. A theoretical model of reading is outlined in support of a causal link between a visual attentional disorder and a failure in reading acquisition.

Attention↗

PubMed2004

Length effect in reading and lexical decision: evidence from skilled readers and a developmental dyslexic participant.

A number of experimental data have shown that naming latency increases with length for pseudo-words but not for frequent real words. Different interpretations have been proposed by current models of reading to account for such a length effect. The aim of the present study was to assess the impact of lexicality on length effect in both the reading and lexical decision tasks. For this purpose, skilled readers were asked to either name or make a lexical decision on words and pseudo-words differing in length from one to three syllables. Skilled readers' results show that length effect is modulated by lexicality in the reading task but no length effect was found in the lexical decision task. The tasks were further proposed to a well-compensated dyslexic participant who exhibited a visual attentional disorder in the absence of any associated phonological problems. A length effect on RTs was found for both words and pseudo-words in lexical decision but naming latencies were affected by length for the pseudo-words only. The present results largely conform to the predictions of the ACV98 model of reading. They are not compatible with the PDP models of reading and can only be partially accounted for by dual route models.

Adult↗

PubMed2004

Lexical orthographic knowledge develops from the beginning of literacy acquisition.

This study reports two experiments assessing the spelling performance of French first graders after 3 months and after 9 months of literacy instruction. The participants were asked to spell high and low frequency irregular words (Experiment 1) and pseudowords, some of which had lexical neighbours (Experiment 2). The lexical database which children had been exposed to was strictly controlled. Both a frequency effect in word spelling accuracy and an analogy effect in pseudoword spelling were obtained after only 3 months of reading instruction. The results suggest that children establish specific orthographic knowledge from the very beginning of literacy acquisition.

Cognition↗