Letter position coding in attentional dyslexia.
Shalev L., Mevorach C., Humphreys GW.
We report data from experiments on orthographic and phonological coding in two patients with attentional dyslexia following bilateral parietal damage. Two experiments required the patients to carry out lexical decisions and we varied whether the nonwords were orthographically or phonologically similar to real words. Experiment 1 showed that the patients were sensitive to the orthographic relations between nonwords and words, as they tended to accept as words nonwords whose letters could migrate within the string to form a word. There were no effects of phonological similarity between the nonwords and the words. Experiment 2 demonstrated that the patients were less likely to accept nonwords as words if the word had to be formed by transposing the first two letters in the string. The data suggest that attentional dyslexics are primarily sensitive to orthographic similarity between words and nonwords, and also that the first letters have privileged coding of their locations, despite the patients being poor at coding letter positions. The implications for theories of visual word recognition are discussed.