Predicting the sources of impaired wh-question comprehension in non-fluent aphasia: A cross-linguistic machine learning study on Turkish and German

In search for common patterns in aphasia: The case of Spanish wh-dependencies

BACKGROUND

Research on comprehension of wh-dependencies in Broca's aphasia has resulted in discrepant findings, suggesting that structurally different languages may involve different comprehension patterns.

AIMS

In the present study, we investigated whether Spanish speakers with Broca's aphasia rely on a language-specific cue that might facilitate comprehension of object wh-dependencies - the preposition a. Since the preposition a in Spanish indicates animate objects, reliance on this cue would facilitate comprehension of more demanding object wh-dependencies, cancelling out processing differences between structures with subject and object extractions.

METHODS

We studied comprehension of subject vs. object quién ("who") and qué ("which") direct and embedded questions, and relative clauses introduced by que in seven speakers with aphasia (SWA): six with Broca's and one with mixed aphasia. Control data were obtained from ten neurologically intact elderly Spanish speakers.

RESULTS

Mann-Whitney test revealed that compared to healthy controls, SWA had preserved comprehension of both subject and object who direct questions, object which direct questions, and object relative clauses. However, they exhibited considerably worse comprehension of subject which direct questions, all embedded questions regardless of the extraction site (subject, object) or type of wh-word (who, which), and subject relative clauses. Individual comprehension profiles obtained in a modified t-test and revised standardized difference test, while containing some variability, largely support lack of subject-object asymmetry and objects-better patterns. Furthermore, in direct questions, comprehension of who questions was better than the comprehension of which questions, while the opposite was found in embedded questions.

CONCLUSIONS

The lack of significant subject-object asymmetry in most conditions, together with better comprehension of object than subject extractions in direct questions, indicates that Spanish SWA rely on the preposition a in the comprehension of object wh-dependencies. However, this strategy fails in more complex conditions (embedded questions), because the processing costs outweigh the facilitating effects of this cue, unless additional cues to the object are present (object relatives). The present findings have implications for the accounts of wh-dependencies in Broca's aphasia involving Discourse-linking, the Intervener hypothesis, and the Competition model.

Comprehension of wh-questions in Turkish-German bilinguals with aphasia: A dual-case study

The aim of our study was to examine the extent to which linguistic approaches to sentence comprehension deficits in aphasia can account for differential impairment patterns in the comprehension of wh-questions in bilingual persons with aphasia (PWA). We investigated the comprehension of subject and object wh-questions in both Turkish, a wh-in-situ language, and German, a wh-fronting language, in two bilingual PWA using a sentence-to-picture matching task. Both PWA showed differential impairment patterns in their two languages. SK, an early bilingual PWA, had particular difficulty comprehending subject which-questions in Turkish but performed normal across all conditions in German. CT, a late bilingual PWA, performed more poorly for object which-questions in German than in all other conditions, whilst in Turkish his accuracy was at chance level across all conditions. We conclude that the observed patterns of selective cross-linguistic impairments cannot solely be attributed either to difficulty with wh-movement or to problems with the integration of discourse-level information. Instead our results suggest that differences between our PWA's individual bilingualism profiles (e.g. onset of bilingualism, premorbid language dominance) considerably affected the nature and extent of their impairments.