Background: Comprehension of semantically reversible sentences is often impaired in Broca's aphasia. When the arguments in such sentences are in derived order, they are more difficult to comprehend than when they are not. Most studies on this topic are of English, a morphologically poor language; only a few experiments have examined sentence comprehension in case-marking languages. These studies tested sentences in which word order was varied while case was kept constant. Their results suggest that case does not improve comprehension of derived order sentences. The present study is on the comprehension of semantically reversible sentences in Turkish Broca's aphasia. Turkish, with its flexible word order and rich case morphology, is well suited to this investigation because there is an interaction between word order and case, which is known to influence sentence production in this aphasia type (Yarbay Duman, Aygen, & Bastiaanse, ).

Aims: The purpose of this study was to investigate the influence of word order and case information on the auditory comprehension of semantically reversible sentences in Turkish Broca's aphasia to find out whether an interaction between word order and case, similar to the one found in production, can be observed in sentence comprehension.

Methods & Procedures: A comprehension test with five reversible sentence types (base order active sentences, sentences with object scrambling, subject relatives, object relatives, and passives) was developed. Sentences in base and derived word order varied in their use of case. Sentences with base case (subject = nominative; object = accusative) and non-base case were included to evaluate the interplay between word order and case separately.

Outcomes & Results: The results showed that both word order and case influenced sentence comprehension. Clauses were comprehended best when there was both base (unambiguous) case and base word order information (base order active sentences). Performance dropped if there was base case information but derived word order (object scrambling and subject relatives). When there was neither base case information nor base word order (object relatives and passives), clauses were comprehended least well.

Conclusions: The sentence comprehension deficit in Turkish Broca's aphasia is due to a problem in assigning thematic roles to the noun phrases by integrating syntactic word order and case information. Such an integration problem is in line with previous findings on sentence production in Turkish and the Integration Problem Hypothesis (IPH: Yarbay Duman, ).