Divergent hemispheric reasoning strategies: reducing uncertainty versus resolving inconsistency

Abstract

Converging lines of evidence from diverse research domains suggest that the left and right hemispheres play distinct, yet complementary, roles in inferential reasoning. Here, we review research on split-brain patients, brain-damaged patients, delusional patients, and healthy individuals that suggests that the left hemisphere tends to create explanations, make inferences, and bridge gaps in information, while the right hemisphere tends to detect conflict, update beliefs, support mental set-shifts, and monitor and inhibit behavior. Based on this evidence, we propose that the left hemisphere specializes in creating hypotheses and representing causality, while the right hemisphere specializes in evaluating hypotheses, and rejecting those that are implausible or inconsistent with other evidence. In sum, we suggest that, in the domain of inferential reasoning, the left hemisphere strives to reduce uncertainty while the right hemisphere strives to resolve inconsistency. The hemispheres’ divergent inferential reasoning strategies may contribute to flexible, complex reasoning in the healthy brain, and disruption in these systems may explain reasoning deficits in the unhealthy brain.

Hemispheric Differences in White Matter Microstructure between Two Profiles of Children with High Intelligence Quotient vs. Controls: A Tract-Based Spatial Statistics Study

“…Recently, Marinsek et al (2014) proposed that both hemispheres diverge by their reasoning strategies. On one hand, the left hemisphere is considered as an interpreter, tending to reduce uncertainty by creating explanations, filling gaps of information, and making inference (Braun and Suffren, 2011).…”

A leftward perceptual asymmetry when judging the attractiveness of visual patterns

“…An interesting question for future research is whether the leftward bias generalises to the judgment of the attractiveness of other types of images such as representational pictures. Research suggests that the LH is more specialised for interpreting and assigning meaning to information (Beaumont, 1985;Gazzaniga, 1998;Marinsek, Turner, Gazzaniga, & Miller, 2014;Zaidel & Edelstyn, 2009) with occipito-temporal regions of the LH processing visual information semantically (Rossion et al, 2000). This may make the LH more suitable for appreciating and evaluating the attractiveness of representational pictures (see also Zaidel & Kasher, 1989), whereas the RH's greater involvement in perceptual and visuo-spatial processing may make it more specialised for the perceptual appraisal of a pattern's elements and how they are configured to form a whole.…”

Hemispheric lateralization in reasoning

“…Instead, they perform simple evaluations like checking a rule or verifying if a statement matches an inference, which may load onto the right hemisphere according to our theory, but which is likely to do so relatively weakly. One of the strengths of Marinsek et al .’s study was that it related evidence from a multitude of tasks to a common set of processes thought to be involved in reasoning. Although this presents challenges—for instance, sifting out the various activation associated with any particular task to identify the activity associated with the putative common underlying process—it might be more straightforward than attempting to parse processes in tasks in which those processes are inextricably linked.…”