Types of Developmental Dyslexia in Arabic

Abstract

Developmental dyslexia is a general term for various kinds of impairments in reading. More than 10 types of developmental dyslexia have been identified, each resulting from a deficit to a different stage in the reading process. The different deficits give rise to different patterns of errors in the various dyslexias and to different types of words that cause difficulty in reading. In this article we present types of developmental dyslexia that we have identified in Arabic, and survey their main characteristics, focusing on the unique properties of the Arabic orthography and their interaction with the manifestation of the various developmental dyslexia types. We present the patterns of developmental peripheral dyslexias, dyslexias that result from impairment at the orthographic-visual analysis stage, and of central dyslexias, which result from impairments at later stages. Within the peripheral dyslexias, we focus on the manifestation in Arabic of letter position dyslexia, which is caused by a deficit in letter position encoding and which results in letter position errors; on attentional dyslexia, a deficit in the attentional window in reading, which results in migrations of letters between words; on visual dyslexia, a deficit in the orthographic-visual analyzer that causes letter omissions, additions, substitutions, and migrations; and on left neglect dyslexia, a disorder that leads to visual errors only on the left side of words. We then report and discuss the manifestation of central dyslexias in Arabic: surface dyslexia—a deficit in the lexical route that causes reading via the sublexical route; vowel dyslexia—a selective impairment in vowel processing in the sublexical route that causes impaired reading of vowel letters; and deep dyslexia—a deficit in the sublexical and lexical routes, which causes reading via the comprehension of the word and leads to semantic and morphological errors. All but one of the dyslexias described here are reported for the first time in Arabic.