Inferencing processes after right hemisphere brain damage: maintenance of inferences

This study was designed to replicate and extend a previous study of inferencing in which some adults with right hemisphere damage (RHD) generated but did not maintain predictive inferences over time (M. Lehman-Blake & C. Tompkins, 2001). Two hypotheses were tested: (a) inferences were deactivated, and (b) selection of previously generated inferences was slowed and not measurable with the original stimuli. Existing literature did not support one hypothesis over the other.

Fourteen adults with RHD and 14 with no brain damage (NBD) participated in this mixed-design study. Participants read short narratives that suggested a predictive inference. Reading times were obtained to assess inference generation, maintenance, and integration.

The majority of participants evidenced generation and maintenance of inferences. For the few who did not maintain inferences, participants with NBD always deactivated the inferences, whereas those with RHD demonstrated either deactivation or slowed selection. Adults with RHD were more likely to exhibit slowing in inference generation and integration.

The results for inference maintenance differ from the original study in that most participants with RHD maintained inferences. Deactivation appeared in both groups, whereas slowed selection appeared to be an aberrant process related to RHD. Future work is needed to tease out the relationships between comprehension, working memory, and inferencing processes.