Harming kin to save strangers: further evidence for abnormally utilitarian moral judgments after ventromedial prefrontal damage

Abstract

The ventromedial PFC (vmPFC) has been implicated as a critical neural substrate mediating the influence of emotion on moral reasoning. It has been shown that the vmPFC is especially important for making moral judgments about "high-conflict" moral dilemmas involving direct personal actions, that is, scenarios that pit compelling utilitarian considerations of aggregate welfare against the highly emotionally aversive act of directly causing harm to others [Koenigs, M., Young, L., Adolphs, R., Tranel, D., Cushman, F., Hauser, M., et al. Damage to the prefrontal cortex increases utilitarian moral judgments. Nature, 446, 908-911, 2007]. The current study was designed to elucidate further the role of the vmPFC in high-conflict moral judgments, including those that involve indirect personal actions, such as indirectly causing harm to one's kin to save a group of strangers. We found that patients with vmPFC lesions were more likely than brain-damaged and healthy comparison participants to endorse utilitarian outcomes on high-conflict dilemmas regardless of whether the dilemmas (1) entailed direct versus indirect personal harms and (2) were presented from the Self versus Other perspective. In addition, all groups were more likely to endorse utilitarian outcomes in the Other perspective as compared with the Self perspective. These results provide important extensions of previous work, and the findings align with the proposal that the vmPFC is critical for reasoning about moral dilemmas in which anticipating the social-emotional consequences of an action (e.g., guilt or remorse) is crucial for normal moral judgments [Greene, J. D. Why are VMPFC patients more utilitarian?: A dual-process theory of moral judgment explains. Trends in Cognitive Sciences, 11, 322-323, 2007; Koenigs, M., Young, L., Adolphs, R., Tranel, D., Cushman, F., Hauser, M., et al. Damage to the prefrontal cortex increases utilitarian moral judgments. Nature, 446, 908-911, 2007].

Figure 1

Typology of moral dilemmas relevant to the present study. Grey boxes represent the contributions of the current study. A summary of results from previous studies on vmPFC involvement in moral judgments about each dilemma type is shown below the dashed line. Low-conflict dilemmas have been examined in previous studies and are not explored in the present work. High-conflict dilemmas involve personal actions and utilitarian justifications, pitting an action that results in a highly aversive, social-emotion arousing harm (i.e., a personal action, such as a directly or indirectly caused aversive harm) against a utilitarian outcome. High-conflict directly-personal dilemmas in the Self condition have been examined in previous studies; here, we added the Other condition. High-conflict indirectly-personal dilemmas are new in the present study. (Two additional types of low-conflict dilemmas are theoretically possible, and we predict would not place demands on the vmPFC, but they were not considered in the present study: (1) a direct, impersonal dilemma (in which the direct harm does not evoke a strong social-emotional reaction) with a utilitarian justification (see Greene et al., 2009 for possible examples) and (2) an indirect, impersonal dilemma without a utilitarian justification.) Example dilemmas: “Footbridge” involves directly pushing a man to his death to save 5 workers. “Switch” involves flipping a switch, indirectly killing your daughter (high-conflict) or a stranger (low-conflict), to save 5 workers. “Architect” involves pushing your boss off of a building to get him out of your life (Greene et al., 2001).

Figure 2

Lesion overlap of vmPFC patients. Mesial and frontal views of the overlap map of lesions for the 9 vmPFC patients. The color bar indicates the number of overlapping lesions at each voxel. The area of maximal overlap lies in the ventromedial prefrontal cortex.

Figure 3

Moral judgments for high-conflict dilemmas of the indirect-self, direct-self, and direct-other type. The proportion of endorsement of the utilitarian option is shown, with error bars reflecting standard error of the mean. The proportion of endorsement was significantly greater for the vmPFC group than the comparison group across all three types of dilemmas, and no interaction effect was observed. In planned follow-up analyses, we found that: (1) When comparing indirect-self versus direct-self dilemmas, there was a main effect of group (vmPFC > Comp) and a trend toward higher proportion of endorsement on indirect as compared to direct dilemmas, but no interaction. (2) When comparing direct-self versus direct-other dilemmas, there was a main effect of group (vmPFC > Comp) and a main effect of perspective (Other > Self), but no interaction.