A new study finds people with higher levels of moral reasoning have greater gray matter volume in brain regions linked to social behavior, decision making and conflict processing, compared with those who have lower levels of moral reasoning.

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People with higher levels of moral reasoning were found to have greater gray matter volume in the prefrontal cortex of the brain.

Hengyi Rao, PhD, a research assistant professor of Cognitive Neuroimaging in Neurology and Psychiatry in the Perelman School of Medicine at the University of Pennsylvania, and colleagues publish their findings in the journal PLOS ONE.

Moral reasoning is defined as a thinking process that humans engage in to determine what is right and wrong in a given situation.

Research in the mid-20th century conducted by psychologist Lawrence Kohlberg revealed that as the cognitive function of humans matures, different stages of moral reasoning are explored. But according to Rao and colleagues, no studies had investigated the brain structures involved in each stage of moral reasoning.

The team set out to address this research gap by enrolling 67 students aged 24-33 who were a part of the Masters of Business Administration (MBA) program at the Wharton School of the University of Pennsylvania.

“MBA students were ideal candidates for this work, as the Wharton curriculum addresses issues of moral decision making and reasoning,” says study co-author Diana Robertson, PhD, a professor of legal studies and business ethics at the Wharton School. “We aimed to investigate whether the stage of moral reasoning is reflected in structural brain architecture.”

All students were required to complete the Defining Issue Test, which seeks to identify the thought patterns, or cognitive schema, a person is using during moral reasoning.

For the test, each student was presented with a moral dilemma, such as medical-assisted suicide. They were then given 12 rationales for each dilemma and were asked to select the relevance of each one.

The students were then assigned to one of seven cognitive schema groups based on their selections, with each group representing the increasing levels of moral reasoning.

Next, the students’ brains were scanned via magnetic resonance imaging (MRI), allowing the researchers to determine the brain structures linked to each level of moral reasoning.

All students also took part in a personality test, after which they were allocated to one of five groups: neuroticism, extraversion, openness to experience, conscientiousness and agreeableness.

Compared with students who had low levels of moral reasoning (defined as not yet having reached the “postconventional” level of moral reasoning), students who had high levels of moral reasoning showed increased gray matter volume in the prefrontal cortex of the brain – the area responsible for mediating conflicting thoughts, choosing between right and wrong and predicting probable outcomes.

What is more, the team found that students who scored higher in openness to experience and lower in neuroticism on the personality tests were more likely to have higher levels of moral reasoning.

Commenting on the findings, Rao says:

This research adds an investigation of individual differences in moral reasoning to the expanding landscape of moral neuroscience.

The current findings provide initial evidence for brain structural difference based on the stages of moral reasoning proposed by Lawrence Kohlberg decades ago. However, further research will be needed to determine whether these changes are the cause or the effect of higher levels of moral reasoning.”

In March, Medical News Today reported on a study published in the British Journal of Developmental Psychology suggesting that children are more likely to share if they respect the morals of their peers.