Vowel letter dyslexia.

This research describes vowel letter dyslexia, a new type of dyslexia characterized by impaired reading of vowel letters. We report a multiple case study of 23 Hebrew readers with vowel letter dyslexia (1 acquired, 22 developmental). They made vowel-letter migrations, omissions, and additions in reading, with significantly fewer errors on consonants, and without vowel errors in speech production. Based on 24 tests that examined various components and the analysis of errors in reading 33,483 words, we ruled out deficits in the orthographic-visual analysis and phonological-output stages, as well as visual, morphological, and auditory deficits. We concluded that vowel letter dyslexia results from a selective deficit in a vowel-letter tier in the sublexical route. Indeed, vowel errors occurred predominantly when the participants read via the sublexical route. Thus, vowel letter dyslexia provides cognitive neuropsychological evidence for the separate processing of vowels and consonants in the sublexical reading route.