Lexical representation and processing of morphologically complex words: evidence from the reading performance of an Italian agrammatic patient.

The study of patients with acquired language disorders has provided crucial evidence for contemporary theories on mental lexical representation. This is particularly true for the representation of morphologically complex words. In this paper we analyzed the performance of a patient (M.B.) affected by agrammatism and dyslexia. M.B. was required to read aloud simple and morphologically complex words. The patient's pattern of errors was interpreted as the result of a predominant use of the lexical routine (phonological dyslexia). Three reading tasks were developed which allowed us to test M.B.'s ability to read morphologically complex words (reading of regular and irregular plurals; reading of high- and low-frequency singular and plural nouns; reading of evaluative suffixes). Errors were determined by frequency effect rather than by type of suffix (i.e., inflectional or derivational). High-frequency morphologically complex items seemed to meet stored representations, thus avoiding the parsing procedures that are required for less frequent items. These results are in keeping with dual route models of lexical representation of morphologically complex words.