When faced with a moral dilemma, are the decisions people make guided by their emotions or rational arguments? A number of studies have suggested that emotions are important for making moral judgments but, according to Ralph Adolphs of the California Institute of Technology in Pasadena, these conclusions have all been based on correlations. About four years ago, he and his colleagues began talking about ways to demonstrate a direct link between emotions and morality.

“We had been thinking about experiments and even gathered some preliminary data, but the project really needed someone to take charge and push it through,” says Adolphs. Graduate students Liane Young in Marc Hauser's lab at Harvard University in Cambridge, Massachusetts, and Michael Koenigs from Daniel Tranel's lab at the University of Iowa in Iowa City took up the challenge.

“We thought it would be interesting to show what happens to moral judgment if emotions are taken out of the picture,” says Young. To do this, she and Koenigs turned to a region of the brain known as the ventromedial prefrontal cortex (VMPC).

Emotion is needed with personal choices that involve a high degree of conflict. Ralph Adolphs

Individuals with lesions in the VMPC have reduced social emotions, such as compassion, shame and guilt — in other words, the types of emotion an individual might use to make moral judgments. People with VMPC damage are of normal intelligence and can understand and remember social and moral norms. In addition, a recent functional imaging study showed that the VMPC is activated when individuals are asked to make moral decisions. On the basis of these results, the team quickly found six patients with damage to the VMPC.

They presented patients and controls with moral situations requiring them to choose between two courses of action. They found controls only made different choices from VMPC patients when presented with certain scenarios. Those that elicited different responses — presumably those in which emotions have a role — involved a 'personal' component. For example, when faced with the option of pushing someone off a bridge to prevent a runaway boxcart from hitting five people, normal individuals have to overcome a 'personal' response against doing harm to an individual in order to agree with the utilitarian, or more pragmatic, response. People with VMPC damage made the utilitarian decision much more frequently, although not in every instance (see page 908).

The distinction between the two groups only occurred when individuals were faced with what were considered 'gut-wrenching' dilemmas. For example, when given the choice of killing their own child to save money the VMPC patients made the same decision — not to kill the child — as normal individuals. But if the scenario was to smother their own child to prevent harm to others, the VMPC patients would more often go for the utilitarian choice. So for certain moral dilemmas, the team concludes, a functional VMPC is needed for 'normal' judgement of 'right' and 'wrong'.

“We found that emotion is needed with personal choices that involve a high degree of conflict,” says Adolphs. The result opens up many questions to investigation. It is not clear, for example, how much emotion plays a part in different moral judgments. To address this, researchers would have to find a way to actually measure the amount of emotional response elicited by different moral judgments, which Young and Koenigs tried to do, but without success. Another limitation of the study is that the moral choices they used were artificial, life-and-death situations. “It would be interesting to see how results might vary if people were faced with more regular moral judgments,” says Koenigs.