Abstract
People vary considerably in moral reasoning. According to Kohlberg’s theory, individuals who reach the highest level of post-conventional moral reasoning judge moral issues based on deeper principles and shared ideals rather than self-interest or adherence to laws and rules. Recent research has suggested the involvement of the brain’s frontostriatal reward system in moral judgments and prosocial behaviors. However, it remains unknown whether moral reasoning level is associated with differences in reward system function. Here, we combined arterial spin labeling perfusion and blood oxygen level-dependent functional magnetic resonance imaging and measured frontostriatal reward system activity both at rest and during a sequential risky decision making task in a sample of 64 participants at different levels of moral reasoning. Compared to individuals at the pre-conventional and conventional level of moral reasoning, post-conventional individuals showed increased resting cerebral blood flow in the ventral striatum and ventromedial prefrontal cortex. Cerebral blood flow in these brain regions correlated with the degree of post-conventional thinking across groups. Post-conventional individuals also showed greater task-induced activation in the ventral striatum during risky decision making. These findings suggest that high-level post-conventional moral reasoning is associated with increased activity in the brain’s frontostriatal system, regardless of task-dependent or task-independent states.
Highlights
Most people have strong moral beliefs about what is right and wrong
To directly test this association, in the present study we examined a sample of 64 Wharton School Master of Business Administration (MBA) students using functional MRI during a resting state without task requirements, as well as during the performance of a monetary risky decision making task
Controlling for variables showing significant group differences (i.e., Openness and Neuroticism), the post-con group showed increased CBF in bilateral ventral striatum (VS), mainly located in the nucleus accumbens extending to putamen and caudate, ventromedial prefrontal cortex (vmPFC) extending to subgenual ACC, and inferior frontal gyrus adjacent to anterior insula (IFG/AIS; peak x, y, z coordinates = [−40, 10, 20]) compared to the pre-con + con group
Summary
Most people have strong moral beliefs about what is right and wrong. the existence of moral values is universal across different cultures and ethnic groups, people vary in their moral development ( called moral reasoning), that is, the ability to analyze complex moral issues[1]. Psychopaths fail to establish this conditioning to make reference to another’s pain, suggesting the important role of value-based reinforcement learning in moral reasoning development in situations such as avoiding outcomes that might hurt others Reward motivation is another possible explanation of individual differences in moral development. According to Kohlberg’s moral development theory, individuals who reach the post-conventional level live by their own ethical principle, including basic human rights as life, liberty, and justice. They tend to pursue “the greatest good for the greatest number of people”[1].it raises the possibility that differences in reward motivation for prosocial behaviors between individuals are associated with different moral development level. We further investigate whether this link extends to the function, in addition to the structure, of the brain’s frontostriatal reward system
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