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.

This study reports the reading of 11 Arabic-speaking individuals with letter position dyslexia (LPD), and the effect of letter form on their reading errors. LPD is a peripheral dyslexia caused by a selective deficit to letter position encoding in the orthographic-visual analyzer, which results in migration of letters within words, primarily of middle letters. The Arabic orthography is especially interesting for the study of LPD because Arabic letters have different forms in different positions in the word. As a result, some letter position errors require letter form change. We compared the rate of letter migrations that change letter form with migrations that do not change letter form in 10 Arabic-speaking individuals with developmental LPD, and one bilingual Arabic and Hebrew-speaking individual with acquired LPD. The results indicated that the participants made 40% letter position errors in migratable words when the resulting word included the letters in the same form, whereas migrations that changed letter form almost never occurred. The error rate of the Arabic-Hebrew bilingual reader was smaller in Arabic than in Hebrew. However, when only words in which migrations do not change letter form were counted, the rate was similar in Arabic and Hebrew. Hence, whereas orthographies with multiple letter forms for each letter might seem more difficult in some respects, these orthographies are in fact easier to read in some forms of dyslexia. Thus, the diagnosis of LPD in Arabic should consider the effect of letter forms on migration errors, and use only migratable words that do not require letter-form change. The theoretical implications for the reading model are that letter form (of the position-dependent type found in Arabic) is part of the information encoded in the abstract letter identity, and thus affects further word recognition processes, and that there might be a pre-lexical graphemic buffer in which the checking of orthographic well-formedness takes place.

Sentence and text comprehension is known to be difficult for orally trained individuals with hearing impairment. This study explored the comprehension of several syntactic structures that are especially difficult for these individuals and may lead them to experience considerable comprehension difficulties. Ten structures derived by wh-movement were tested, some of them for the first time in hearing impairment research: five types of relative clauses, three types of wh-questions, and two types of topicalized structures, compared with two types of simple sentences. Experiment 1 tested subject and object relatives using a sentence–picture matching task. Experiment 2 tested subject questions and object questions using a picture selection task. Experiment 3 tested subject and object relatives using comprehension questions. Experiment 4 tested subject and object relatives and topicalized sentences using a reading and paraphrasing task. The participants were 24 orally trained Palestinian Arabic speaking individuals, 21 of them had mild to profound binaural hearing loss, and 3 had monaural hearing loss. The participants with binaural hearing impairment, who were not sufficiently exposed to language input during the first year of life, failed to understand object relatives, object questions, and topicalization in subject–verb and verb–subject orders in both Palestinian Arabic and Standard Arabic. In some tasks, they even had difficulty understanding subject relatives and subject questions. The monaurally hearing impaired performed similarly to the controls on all tasks.