As discussed above, moral judgments involve both emotions and cognition, and the importance of either one will depend on the particular circumstances involved. Joshua Greene, Jonathan Cohen, and colleagues asked people to consider the trolley problem and similar scenarios while undergoing fMRI brain imaging. The authors divided their moral dilemmas into moral-personal and moral-impersonal scenarios.

The trolley scenario that required killing someone directly (i.e., pushing the large man in front of the trolley) is an example of a moral-personal scenario. The trolley problem that did not demand direct, physical contact with the man who would be killed (i.e., pulling the switch) is an example of a moral-impersonal scenario. When people thought about moral-personal scenarios, the medial frontal and anterior cingulate regions lit up. The medial frontal region is associated with the processing of interpersonal relations and, possibly, empathy. The anterior cingulate is associated with processing conflicting messages from different parts of the brain. When people considered the moral-impersonal scenarios, the dorsolateral frontal regions were most active. The dorsolateral frontal region is involved with rational thought and analysis.

This suggests that the farther away we are from the human cost of our actions, the more our moral decisions are based on cold rational analysis, rather than gut emotion. These kind of rational moral decisions are known as utilitarian judgments, and involve a kind of cost/benefit analysis.