We used positron emission tomography (PET) to investigate the neural mechanisms underlying the willingness to forgive another person's moral transgression involving deception. During scanning, 12 subjects were asked to judge the forgivability of a perpetrator's moral transgression. These transgressions were described by four kinds of scenarios composed of a combination of two factors: the attitude of the perpetrator (dishonest or honest) and the severity of the moral transgression (serious or minor). Behavioral data showed that both the perpetrator's dishonesty and the seriousness of the scenario decreased the subjects' willingness to forgive the moral transgression. Neuroimaging data revealed that, relative to honest responses, a perpetrator's dishonest responses were associated with right ventromedial prefrontal activity, which possibly reflects the subjects' identification of the perpetrator's deception. The opposite comparison did not show significant activation. Moreover, a comparison of serious scenarios with minor scenarios did not reveal significant activation. Instead, minor scenarios, relative to serious scenarios, evoked activity in the right middle frontal gyrus and the right caudate nucleus, possibly reflecting increased demand on frontal control system function. Further analysis revealed that the left ventromedial prefrontal cortex showed a significant interaction between the two factors, indicating that this region functions as a mediator of the two factors, modulating judgments regarding the forgivability of moral transgressions. Taken together, these findings suggest that the ventromedial prefrontal cortex plays a key role in the forgiveness of moral transgressions involving deception.
- Ventromedial prefrontal cortex