Effects of syntactic complexity, semantic reversibility, and explicitness on discourse comprehension in persons with aphasia and in healthy controls

Purpose: Prior studies of discourse comprehension have concluded that the deficits of persons with aphasia (PWA) in syntactically based comprehension of sentences in isolation are not predictive of deficits in comprehension of sentences in discourse (Brookshire & Nicholas, 1984; Caplan & Evans, 1990). However, these studies used semantically constrained sentences in discourse, which do not require syntactic analysis to be understood. A discourse task was developed to assess the effect of syntactic complexity, among other factors, on discourse comprehension in PWA. Method: Thirty-eight PWA and 30 neurologically healthy control participants were presented with passages that contained 2-3 semantically reversible sentences that were either syntactically simple or syntactically complex. The passages were presented auditorily, and comprehension was assessed with the auditory and written presentation of 4 multiple-choice questions immediately following each passage. Results: Passages with syntactically simple sentences were better understood than passages with syntactically complex sentences. Moreover, semantically constrained sentences were more likely to be accurately interpreted than semantically reversible sentences. Comprehension accuracy on our test correlated positively with comprehension accuracy on an existing test. Conclusion: The presence of semantically reversible, syntactically complex sentences in a passage affects comprehension of the passage in both PWA and neurologically healthy individuals.