Suppression and inference revision in right brain-damaged and non-brain-damaged adults

This study examined the extent to which participants were able to inhibit, or suppress, initial inferences that were rendered inappropriate by subsequent information and the relation between suppression ability and discourse comprehension in adults with right hemisphere brain damage (RBD). Two-sentence stimuli were presented auditorily to 32 adults with RBD and 17 control subjects. An ambiguous initial stimulus sentence elicited both dominant and less-preferred inferences and the second sentence resolved the ambiguity toward the initially less likely interpretation. Subjects judged whether a probe word fit with the meaning of the entire stimulus. To evaluate suppression function, probe words were chosen to represent the dominant, but eventually inappropriate inference for the first sentence. In a comparison condition, the same probes were paired with inferentially unambiguous stimuli. Accurate 'no' judgments of the probe words were slower in the ambiguous condition than in the unambiguous condition, reflecting interference from the dominant but eventually inappropriate interpretations of the ambiguous stimuli. This interference did not subside for either group over two probe intervals (850 and 1200 ms), indicating that neither group as a whole suppressed the unwanted inferences over time. However, on a within-group level, RBD subjects' effectiveness at suppressing these inappropriate inferences was related to their comprehension of discourse stimuli that required inference revisions.