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RESEARCH STUDY

RESEARCH

The Cognitive Deficits Responsible for Development of Dyslexia

AUTHOR:

Sylviane Valdois

SPONSOR/INSTITUTION:

CNRS (GIS "Sciences de la Cognition" - Joint Activities Award Scheme from the British Academy

YEAR PUBLISHED:

2004

PUBLICATION:

Dyslexia

KEY HIGHLIGHTS:

  • This paper discusses 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, this paper argues that the visual attentional deficit hypothesis does.

SUMMARY

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.


This paper discusses 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, this paper argues 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.