Grammatical ambiguity resolution in right hemisphere-damaged patients: Evidence from an insertion task

We examined the issue of right cerebral hemisphere (RH) participation in sentential syntax processing. A modified version of the Insertion Task of Schneiderman and Saddy (1988) was administered to eight right hemisphere brain-damaged (RHD), eight left hemisphere brain-damage (LHD) and 28 right-handed control (CTR) subjects: 28 word/syntagm insertions required role reassignment of a lexical item in the stimulus sentence (Shift); 25 insertions implied only semantic reinterpretation of the sentence (Nonshift). Age, formal education, cognitive proficiency, mood and verbal intelligence were introduced as covariates in the analysis of the outcomes to partial out their influence on performance. The LHD group outperformed the RHD patients on the Shift items, though both scored similarly on other language tasks. The RHD group performed significantly worse only on the Shift items. However, there were no differences between the RHD and CTR Nonshift scores, or between the LHD and CTR Shift scores. Again, the RHD group scored loafer than both the CTR and the LHD subjects on the Insertion Task as a whole. Results are discussed in relation to previous findings, and an associative model approach to sentence processing is proposed as an explanatory framework. The findings suggest that the RH may be crucial for parallel activation processes underlying resolution of grammatical ambiguity.