Impact of brain damage on moral judgment.

Aim: This study aimed to determine the effects of damage to various brain regions on moral judgment using a novel third-party punishment task with fully manipulated conditions.

Methods: We assessed 35 individuals with brain damage (26 with frontal lobe and nine with non-frontal lobe damage) and 30 healthy controls (HCs) using a moral judgment task consisting of 40 vignettes across five conditions, with varying degrees of intentionality and consequences. Participants rated the protagonist's "badness" and their aroused feelings. Cognitive impairments and empathetic traits were also assessed.

Results: Compared to HCs, individuals with brain damage judged protagonists to be more blameworthy than did HCs in vignettes where harmful intentions were absent (No Negligence, p = 0.02; No Harm, p = 0.02). The order of moral judgment ratings across conditions was consistent between groups, indicating preserved knowledge of social/moral norms in brain-damaged individuals. Although these are preliminary results, there are no significant differences in moral judgment ratings between individuals with frontal and non-frontal lobe damage.

Conclusion: This study revealed that individuals with damage to diverse brain regions show excessive punitive tendencies toward the actions of others without malicious intention. These effects cannot be fully explained by changes in empathy or emotional responses. Moral judgment ratings did not significantly differ between individuals with frontal and non-frontal lobe damage. However, given the small sample size of the non-frontal lesion group, these findings should be interpreted with caution, and further research is necessary to confirm this conclusion.