Word-form dyslexia.

In this study we have reported our investigation of two patients with an acquired dyslexia characterized by letter-by-letter reading, whole word reading being apparently impossible. It has been shown that this phenomenon of letter-by-letter reading cannot be accounted for by visual or perceptual factors nor by impairment of visual span of apprehension. The exceptionally slow speed of reading was documented and a clear relationship between word length and reading speed established. Performance on tasks considered to maximize whole word reading which at the same time prevent the possibility of letter-by-letter reading, namely, reading script and reading with tachistoscopic presentation, was impaired. The satisfactory performance of these two patients on tasks of picture interpretation suggests that the two components of the syndrome simultanagnosia, letter-by-letter reading and piecemeal perception of complex scenes, are dissociable. Three alternative explanations of letter-by-letter reading are considered and we conclude that in this type of acquired dyslexia there is damage to the system through which a visual word-form is attained.