Comprehension of word order in Turkish aphasia

Background People with aphasia (PWA) have been shown to encounter difficulties in processing sentences with non-canonical (i.e., derived) word order. Although previous research points to similar impairment patterns in non-canonical structures in aphasia across many languages, there is only little agreement among authors why PWA experience these impairments. Aims This study aims to unveil whether and how far fluent and non-fluent PWA speaking Turkish, a flexible word order language, are impaired in comprehending different conditions of word order alignments in declarative sentences. Methods & Procedures Using a picture-matching paradigm, we examined two groups of Turkish speakers with aphasia: fluent PWA (n = 7) and non-fluent PWA (n = 10), and a matched reference group of non-brain-damaged controls (NBDs, n = 16). Participants listened to simple declarative sentences in four conditions: Subject - Object - Verb (SOV), SVO, OVS, and OSV. They were asked to point to the corresponding visual display that best depicts the sentence. Data were analysed with generalized linear mixed-effects regression models in R. Outcomes & Results Our findings have shown that the PWA performed less well than the NBDs overall, and that while the fluent PWA showed no condition differences at all, the non-fluent PWA performed worse in object-first (OVS/OSV) sentences than subject-first sentences (SOV/SVO), and no further condition differences were found. Conclusions We discuss that the data presented in this study support the theories that (i) predict derived structures to be affected in aphasia and that (ii) hold lexically restricted sentence material between moved objects and their base-generated positions to pose challenges in aphasic sentence comprehension. We also suggest that high structural frequency of subject-first sentences might have worked in favour of the PWA, rendering the comprehension of these structures easier to process.