The triple-deficit hypothesis in Arabic: Evidence from children with and without dyslexia

This study investigated the triple-deficit hypothesis in Arabic, a Semitic transparent orthography, among 258 native Arabic children from Grade 3, divided into a typical readers group (n = 204) and a dyslexia group (n = 54). Children were tested on word- and pseudoword-reading accuracy, word-reading fluency, phonological awareness (PA), naming speed (NS), orthographic processing (OP), and nonverbal reasoning ability. The results indicated that all children with dyslexia had either double or triple deficits, and none of them had a single deficit. Children with triple deficits showed lower performance than children with single and no deficits on all the reading measures. They have also lower performance to children with double deficits on word-reading accuracy but comparable scores in word- and pseudoword-reading fluency. In addition, OP was confirmed as an additional independent predictor of word-level reading skills besides PA and NS, while controlling for age and nonverbal intelligence. The classification findings showed that the presence of a triple deficit maximizes the risk of reading failure. These findings support the additive nature of combined deficits in PA, NS, and OP. Moreover, they establish the benefit of including OP as a third deficit, in addition to PA and NS, underlying dyslexia in Arabic.