Real-time processing in reading sentence comprehension for normal adult individuals and persons with aphasia

Background: Persons with aphasia (PWA) have shown difficulties in integrating linguistic materials over time and distance in sentence processing. However, few studies have investigated sentence-processing difficulties among PWA as reflected in online processing measures. Furthermore, relatively few studies have examined the online processing of syntactically simple but computationally demanding sentences among PWA. Such sentences are important from the perspective of resource-related theories of aphasic language deficits, which predict that such sentences should be challenging for PWA even if the syntactic structures involved are not. Aims: The purpose of the study was to investigate the sentence-level online reading times of normal adult individuals (NAI) and PWA by word category and as a function of adjective padding. It was assumed that head nouns entail greater processing costs than determiners because they represent the point at which integration of material within a noun phrase must take place. It was also assumed that increasing adjectival padding within a noun phrase requires more integration and creates greater processing costs. Methods & Procedures: A total of 30 NAI and 30 PWA participated in the current study. Sentence stimuli were obtained from the Computerised Revised Token Test (CRTT) (McNeil et al., 2008). Sentences were presented using a non-cumulative (Word Fade = _WF) self-paced word-by-word reading method (CRTT-R-_WF). Reading times for the determiners and the correct nouns were analysed. Outcomes & Results: Both groups showed significantly longer reading times for the nouns than for determiners and in two-adjective than in one-adjective conditions. Furthermore, the reading times for the two-adjective condition were significantly longer than the one-adjective condition for nouns but not determiners across the groups. The PWA exhibited significantly longer overall reading times, as well as significantly longer reading times on the nouns than the NAI. Conclusions: Increased linguistic integration costs-imposed by greater amounts of material to be integrated, and appearing at the point where integration must take place-differentiated reading-time performance between the NAI and PWA participant groups. The PWA showed differentially longer online processing times for elements that imposed high integration costs. This difference appeared most dramatically when two adjectives intervened between the determiner and the head noun. The current results are consistent with resource-related hypotheses regarding aphasic language deficits, which suggest that PWA with limited control of processing resources should show differentially greater impairments in sentence processing as compared to NAI.