Abnormal moral reasoning in complete and partial callosotomy patients

Abstract

Recent neuroimaging studies suggest lateralized cerebral mechanisms in the right temporal parietal junction are involved in complex social and moral reasoning, such as ascribing beliefs to others. Based on this evidence, we tested 3 anterior-resected and 3 complete callosotomy patients along with 22 normal subjects on a reasoning task that required verbal moral judgments. All 6 patients based their judgments primarily on the outcome of the actions, disregarding the beliefs of the agents. The similarity in performance between complete and partial callosotomy patients suggests that normal judgments of morality require full interhemispheric integration of information critically supported by the right temporal parietal junction and right frontal processes.

Shifting Gears: Seeking New Approaches for Mind/Brain Mechanisms

“…It also would predict that a split-brain patient, when talking about his choices on tests that probe such moral values, might be more utilitarian in his outlook than would normal controls. After all, and because of their callosal disconnection, the area of the brain managing the beliefs of others was now disconnected from the part of the brain considering a moral dilemma from the perspective of the personal self (Miller et al 2010). Incredibly, that is exactly what was found.…”

“…responded on the basis of the outcome and not the belief, i.e., he said it was permissible. Moments later, though, as if that didn't seem right to his verbal left hemisphere, he spontaneously offered that "sesame seeds are tiny little things, they don't hurt nobody" (Miller et al 2010). This rationalization offered by J.W.…”

Hemispheric lateralization in reasoning

“…Although the left hemisphere is able to draw inferences and generate explanations, it is less capable of revising those explanations. When instructed specifically to adopt a new strategy, the left hemisphere seems to be able to do so, but there are also cases wherein the left hemisphere perseverates with an explanation even in the presence of new information (but without explicit instructions to update) . The left hemisphere is also prone to errors of commission.…”

The split brain: A tale of two halves

“…The aim was to find out whether the patients felt that someone who intends to poison his boss but fails because he mistakes sugar for rat poison, is on equal moral ground with someone who accidentally kills his boss by mistaking rat poison for sugar 7 . (Most people conclude that the former is more morally reprehensible.)…”