On the role of stems and prefixes in reading complex nonwords: Evidence from individuals with and without acquired dyslexia.

The role of stems and prefixes in complex nonword reading was investigated in unimpaired readers and five individuals with acquired dyslexia. All participants completed a reading aloud task (and the reading impaired individuals also completed a repetition task) with four different types of nonwords: prefix + stem (), non-prefix + stem (), prefix + non-stem (), non-prefix + non-stem (); and prefixed and non-prefixed filler words. The unimpaired readers responded fastest to nonwords containing two morphemes (prefix + stem), slower to nonwords with one morpheme (non-prefix + stem; prefix + non-stem), and slowest in the non-morphemic control condition (non-prefix + non-stem), providing evidence for the added benefit of prefixes and stems during reading. The five reading impaired individuals showed facilitatory morpheme effects across both tasks, but stem-effects were more robust than affix-effects. There was no difference between the prefixed and non-prefixed words in any of the data. The impact of morphological structure on nonword reading and repetition points to the important role of morphemes across different modalities..