Contextual bias and predictive inferencing in adults with and without right hemisphere brain damage

Background: Impaired inferencing has been suggested to contribute to the comprehension deficits exhibited by adults with right hemisphere brain damage (RHD); however, conflicting results exist concerning the inferencing deficits associated with RED. Although inference generation has been examined in most of the previous studies, little information is available regarding other processes, such as maintaining inferences over time, the plausibility of inferences in different contexts, and how contextual bias affects these inferencing processes. Aims: The purpose of the study was to examine the influence of contextual bias on the inferencing processes of older adults without brain damage (NBD) and adults with RHD. It was expected that the NBD group would show clear effects of contextual bias. In contrast, the RHD group was expected to use strong contextual bias to guide inferencing, but to have more difficulty in stories that contained weaker contextual bias. Methods & Procedures: A total of 18 older adults without brain damage and 8 individuals with RED participated in the study. Participants in the RHD group were selected on the basis of a lesion in the right hemisphere, and not the presence of a communication disorder. None evidenced neglect, and as a group they performed similarly to the NBD group on measures of language and working memory. Thinking Out Loud protocols were used to examine the generation, maintenance, and likelihood of predictive inferences, as well as generation of alternative inferences in stories with a low or high probability that a specific outcome would occur. The study was constructed as a mixed design, with group as a between-subjects variable and story condition as a within-subjects variable. Outcomes & Results: Results suggest that contextual bias influenced inference processes in both healthy older adults and individuals with RHD. Both groups used context to qualify the likelihood of inferences, but adults with RHD were less adept at using context to maintain inferences and to restrict inference generation to the most likely outcomes. Conclusions: Adults with RHD who have minimal language deficits can generate predictive inferences and use context to guide some inferencing processes, although they do not use context to constrain inferencing as much as healthy older adults do. The results provide potential insight into the nature of comprehension deficits that may occur after RHD, but the small sample of individuals with minimal cognitive-communication impairments precludes generalisation of the findings to the larger clinical population of adults with RHD.