March 22, 2007
Study Links Emotions And Moral Judgment
Would you smother a baby to save the lives of a room full of people? Faced with this hypothetical scenario, most people would let emotion override cold, hard logic.
But scientists investigating the role of emotion in moral judgments have found that damage to a particular region of the brain, critical for emotional processing, seems to eliminate the emotional component, leaving only the rational response to this type of moral dilemma.
The research, led by scientists from the University of Iowa, with collaborators from the California Institute of Technology, the University of Southern California and Harvard University, shows that a brain region called the ventromedial prefrontal cortex (VMPC) is critical for resolving moral dilemmas that normally provoke strong negative emotions. The results support the idea that emotion is a necessary component of the decision-making process in certain personal moral dilemmas.
The study, which appears in the journal Nature's Advance Online Publication March 22, found that individuals with bilateral damage to the VMPC made abnormal judgments in response to moral dilemmas that pitted the "greater good" against an action that is highly emotionally aversive.
For example, in hypothetical scenarios that involved personally harming or even killing one individual in order to save the lives of several people, VMPC patients were significantly more likely to choose the "utilitarian" option -- sacrificing one to save many -- than were neurologically normal individuals or individuals with brain damage to regions other than the VMPC.
In contrast, the VMPC patient's judgments in less emotionally charged moral dilemmas did not differ from those made by neurologically normal individuals or patients with non-VMPC brain damage.
"For moral dilemmas where the aggregate welfare of many people is pitted against a highly emotional aversive act, like smothering a baby, for example, there appear to be two important reasoning systems for resolving the dilemma. One is an emotional/intuitive system; the other is a rational, cold, hard reasoning system. These findings show that those systems are separate and appear to be separable in terms of the brain systems because the VMPC patients are missing the emotional system but not the rational one," said Daniel Tranel, Ph.D., UI professor of neurology and psychology and study author.
Previous studies have shown that patients with VMPC damage generally have blunted emotional responses and reduced social emotions like empathy or embarrassment. Despite these emotional disruptions, these patients are otherwise cognitively normal.
The findings suggest that the VMPC plays a critical role in determining right and wrong in situations that evoke strong negative emotions, and therefore suggest that emotion must be a necessary component of the decision-making process in this subset of moral dilemmas.
This idea has been hinted at in functional imaging studies, but the current study with patients who have neurologically defined damage provides direct evidence for the role of the emotion-generating brain system in moral judgments. Tranel noted that the patient registry of the Division of Cognitive Neuroscience at the UI was an important resource for this study, allowing the researchers to recruit patients with specific neurological characteristics in order to answer specific research questions.
In addition to Tranel, the research team included Ralph Adolphs, Ph.D., the Bren Professor of Psychology and Neuroscience at Caltech, and Michael Koenigs, Ph.D., who was first author of the study and currently is at the National Institute of Neurological Disorders and Stroke, Bethesda, MD. Koenigs was a graduate student in Tranel's UI lab when the study was conducted. Also part of the team were Marc Hauser, Ph.D., a professor of psychology, organismic & evolutionary biology and biological anthropology at Harvard University, Cambridge, Mass., and Liane Young and Fiery Cushman, students in Hauser's lab; and Antonio Damasio, M.D., Ph.D., the David Dornsife Chair in Neuroscience and professor of psychology, University of Southern California, and director of the Brain and Creativity Institute and Dornsife Center for Cognitive Neuroimaging at USC. Damasio also is a distinguished adjunct professor at the UI.
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