A Visually Based Developmental Reading Deficit

This study describes a developmental reading disability and identifies a deficit of visual perception as the underlying cause. A.H., a university student with apparently normal reading comprehension, was severely impaired in reading aloud isolated words (e.g., dear → "pear") and sequences of unrelated words (e.g., pouch cedar culture jacket → "cedar pouch jacket culture"). Eight experiments involving several visual presentation conditions convincingly linked her impaired reading performance to a developmental deficit in perceiving the location and orientation of visual stimuli. Four additional experiments demonstrated that A.H. achieves good comprehension for meaningful material by exploiting knowledge-based constraints (e.g., syntactic constraints) to "repair" the errors introduced by her visual system. These results have implications for research on developmental dyslexia, normal reading, and normal vision.