Deficient morphological processing in adults with developmental dyslexia: another barrier to efficient word recognition?

Research on dyslexia has focused on the phonological level of linguistic analysis. Here we extend the investigation of the linguistic competence of individuals with dyslexia to the morphological level of linguistic analysis. We examine whether adult Hebrew readers with dyslexia extract and represent morphemic units similarly to normal readers. Using the priming paradigm in the word fragment completion task, we measured the magnitude of morphological priming and contrasted this effect with the repetition priming effect. Students with normal reading ability showed the typical repetition priming effect. A comparable repetition priming effect was also found for the dyslexic group as a whole. However, when the dyslexics were classified into three subtypes according to their phonological and orthographic decoding skills, repetition priming effects were significant only for the phonological dyslexia subgroup but not for the surface or mixed dyslexia subgroups. Furthermore, students with normal reading ability showed strong morphological priming, comparable in strength to the repetition priming effect. In contrast, the dyslexic readers did not show morphological priming, neither the dyslexia group as a whole, nor any of the subgroups. Our results highlight an additional source for dyslexics' difficulties with word recognition which lie at the level of morphological processing.