A right-hemispheric advantage for fast inferential reasoning
Maria Eckstein1, Silvia A. Bunge1; 1University of California, Berkeley
It has long been known that the two hemispheres contribute differentially to cognition, most prominently in language. In the field of inferential reasoning, one hypothesis is that the left hemisphere produces inferences whenever there are gaps in logic, and that the right hemisphere rejects those inferences that lead to conflict (Marinsek et al., 2014). To shed more light on the hemispheric division of labor, we asked 37 right-handed participants to work on an inferential reasoning task, in which stimuli were presented laterally at a fast pace, such that one hemisphere had a processing advantage compared to the other. The task required participants to determine whether a series of stimuli conformed to pre-specified rules (“SET”) or whether it violated these rules (“noSET”). We found that participants recognized SETs faster when stimuli were presented to the right than left hemisphere, F(1,55)=5.0, p=0.028. A similar advantage arose when participants used their (non-dominant) left hand, controlled by the right hemisphere, F(1,33)=8.5, p=0.0064. Accuracy showed the same, albeit non-significant, right-hemispheric advantage for recognizing SETs. No hemispheric differences were evident for noSETs. This suggests that in the current paradigm, the right hemisphere was specifically involved in confirming inferences, an extension to the framework introduced above (Marinsek et al., 2014). This advantage for recognizing regular patterns among a set of stimuli is in accordance with the right hemisphere’s role in global processing (Robertson & Lamb, 1991). Our results further suggest a role of the right hemisphere in rapid (versus slow) computation, more generally.
Topic Area: THINKING: Reasoning