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Related Experiment Video
Updated: May 23, 2026

Assessing Dyslexia at Six Year of Age
Published on: May 1, 2020
Impaired letter-string processing in developmental dyslexia: what visual-to-phonology code mapping disorder?
Sylviane Valdois1, Delphine Lassus-Sangosse, Muriel Lobier
1Laboratoire de Psychologie et NeuroCognition (UMR CNRS 5105), Grenoble, France. Sylviane.Valdois@upmf-grenoble.fr
This study challenges the phonological theory of developmental dyslexia. Findings indicate that poor letter processing in dyslexic children is not due to phonological mapping issues but rather visual familiarity.
Area of Science:
- Cognitive Psychology
- Developmental Neuroscience
- Linguistics
Background:
- Developmental dyslexia is often linked to poor visual attention (VA) span, affecting multi-character processing.
- Previous research suggested poor letter/digit-string processing in dyslexia, but preserved symbol-string processing, pointed to a visual-to-phonology code mapping deficit.
- This interpretation aligns with the phonological theory of developmental dyslexia.
Purpose of the Study:
- To investigate the visual-to-phonological-code mapping disorder hypothesis in developmental dyslexia.
- To differentiate between phonological deficits and visual familiarity accounts for processing differences in dyslexic children.
Main Methods:
- Experiment 1: Assessed letter-string, digit-string, and color-string processing in dyslexic children to distinguish between phonological and visual familiarity explanations.
- Experiment 2: Evaluated letter-string report performance with and without a concurrent taxing phonological task to assess phonological interference.
Main Results:
- Experiment 1 revealed poor letter/digit-string processing but preserved color-string processing in dyslexic children, supporting a familiarity account over a visual-to-phonology mapping disorder.
- Experiment 2 demonstrated that dyslexic children's letter-string report was equally impaired regardless of whether a concurrent phonological task was performed.
Conclusions:
- The findings strongly refute a phonological account for poor letter-string processing in developmental dyslexia.
- Results suggest that visual familiarity, rather than visual-to-phonology code mapping deficits, better explains processing differences observed in dyslexic individuals.

