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.