Noun vs. Verb processing in aphasia: new data from matched comprehension and production tasks.

INTRODUCTION: Existing studies in aphasia show conflicting results regarding the presence and the nature of differences between nouns and verbs across comprehension and production modalities. While studies generally report greater difficulty with verb production, the results are more mixed for comprehension tasks. In this study, for the first time, we directly compare noun and verb processing using fully balanced, parallel tasks for both comprehension and production in a large sample of Russian-speaking individuals with aphasia.

METHOD: We analyzed data from 156 individuals with post-stroke aphasia. Participants completed four tasks from the detailed language assessment tool in Russian (Russian Aphasia Test): noun comprehension, verb comprehension, object naming, and action naming. Tasks were carefully matched for key psycholinguistic variables, allowing for direct comparison of performance.

RESULTS: Participants performed significantly better on comprehension tasks than on production tasks. Crucially, across both modalities, nouns had higher accuracy than verbs. Error analysis revealed differing patterns: semantic paraphasias were more common in action naming, while phonological paraphasias predominated in object naming.

CONCLUSIONS: The results indicate that word production is more impaired than comprehension in individuals with aphasia, reflecting the greater demands of lexical retrieval relative to semantic recognition. Verbs were consistently more difficult than nouns across modalities, supporting a modality-general noun-verb dissociation. The greater difficulty associated with verbs likely stems from their increased grammatical and semantic complexity, as also evidenced by the higher rate of semantic errors in verb production. In all, these findings have significant implications for models of lexical processing and clinical assessments.