Morphological vs. Phonological Explanations for Affix Errors in Agrammatism

Background: There has been no consensus as to what explains the well-attested problems with inflection in individuals with agrammatic aphasia. Some studies point to a predominantly phonological influence while others view morphological factors as primary. Aims: The present study aims to investigate what morphological and phonological factors influence the production of inflectional suffixes in agrammatism. Methods & Procedures: Seven non-dysarthric and non-apraxic English-speaking agrammatic patients (mean age 53.2 years, range 35–69 years, at least 2 years post onset) were given a production task in which the morphological or phonological complexity of the environment of the inflectional morpheme was varied. Outcomes & Results: Analysis indicates that morphological factors (number and type of morpheme, real vs. pseudo stems), rather than phonological factors (sonority, suffix syllabicity, stem length) resulted in significantly higher error rates. Conclusion: Once morphological and phonological influences are teased apart in a controlled experiment, we see that morphological environments in the production of affixed forms in agrammatic aphasia play a greater role than phonological factors.