Letter Position Dyslexia in Fingerspelling: Similar Error Patterns in Reading Written and Fingerspelled Words.

Letter position dyslexia is a deficit in letter position encoding in the orthographic-visual analysis stage. We report here the first cases of deaf signers who show letter position dyslexia in both written and fingerspelled words. Their error pattern was identical in the two modes of presentation, written and fingerspelled: in both modes, they had almost only within-word letter transpositions; their transpositions involved middle letters and almost never exterior letters; they had errors of doubled letters; and their errors occurred almost only in migratable words. They showed no transpositions in reading multi-digit numbers. These results indicate that despite the temporal separation between the fingerspelled letters, the reading of fingerspelling uses the same cognitive processes, and specifically, the same letter-position-encoding mechanism, as the reading of written words.