A recent paper in the Journal Nature, Damage to the Prefrontal Cortex Increases Utilitarian Moral Judgments (Nature, advance online publication March 21, 2007), has provided strong evidence that we are indeed moral animals, and that certain aspects of our moral behavior are hardwired in our brain. The institutions involved in this research (U. Iowa Dept. of Neurology, Harvard U. Dept. of Psychology, and the Brain and Creativity Institute at the U. Southern California) reflect the multi-disciplinary approach required for such a study.
Where in the brain is morality?
Our brain is organized in layers, somewhat like an onion. The deepest layer, like the brain stem and the structures around it, is the most ancient, or primitive, from an evolutionary point of view. These structures control vegetative functions, like heart rate, breathing, gastrointestinal motility, etc. These functions are essential for life and are shared by organisms from the most primitive to the most complex.
Next in evolution came another layer of behavioral complexity: diverse functions such as thirst, hunger, sexual attraction, fight-or-flight responses to danger, responses to day-light cycles, and short- and long-term memories. These functions are mediated by structures deep inside the brain called the midbrain. The midbrain contains structures, such as the amygdala (fight or flight, rage, aggression), the hypothalamus (hunger), the nucleus accumbens (reward, pleasure) and the hippocampus (memory). These functions are not voluntary; they are found in mice and humans alike.
A more recent layer of the brain tissue, called prefrontal cortex, was added when monkeys started to evolve. In this layer resides the ability to function as a social animal, for instance, traits like empathy and moral judgment. The last and outermost layer, added relatively recently, is called the frontal cortex. It is most developed in humans. Messages from the brainstem, midbrain, and prefrontal cortex feed into this area (situated right behind the eyes), where they are all integrated, weighed, judged, contemplated, and then translated into action.
What did the Nature paper find?
It has been suspected for about 10 years that an area within the prefrontal cortex, called the ventromedial prefrontal cortex or VMFC, is required for emotions and moral judgments. When subjects in a brain imaging study were presented with a scenario requiring moral judgments, the area that lit up was the VMFC. What kind of situations were they? Highly aversive ones; for instance, sacrificing one person in order to save several others. The anguish of such decisions is captured in Sophie’s Choice, or in King Solomon’s famous trial of the two women.
The vast majority of people will recoil from making a “utilitarian” calculation of killing one person so as to save others. Indeed, in this experiment, over 80% refused this option. But in a group of 6 patients who had some kind of pathology in their VMFC, such as an aneurysm or a tumor, the judgment was completely utilitarian—kill the few to save the many. No hesitation, no compunction. In fact, Antonio Damasio, one of the authors of the present study, published a study in 1999 of two patients who have had a defect in their VMFC since infancy (Nature Neuroscience vol. 2, pp. 1032-1037, 1999). As adults, the two early-onset patients had severely impaired social behavior despite normal basic cognitive abilities. They showed insensitivity to future consequences of decisions, defective autonomic responses to punishment contingencies, and failure to respond to behavioral interventions. The authors concluded, “Thus early-onset prefrontal damage resulted in a syndrome resembling psychopathy.”
What does it all mean?
The implications of these studies are enormous. For instance,
- We may finally get a handle on extreme psychopathic behavior, such as serial killing, serial raping, extreme levels of domestic violence.
- Our legal system will have to, sooner or later, come to grips with criminal behavior engendered by structural defects in the brain. Evidence of brain imaging (fMRI) is already being introduced in court, and juries are becoming receptive to the evidence.
- On a more hopeful note, but probably less imminent, we may learn one day how to intervene and enhance individuals’ moral judgments. Wouldn’t that be a welcome development of this “1984 science”?
Moral philosophers have dismissed evolutionary biologists and neuroscientists forays into the realm of ethical and moral judgment. They are now having second thoughts, and the more intellectually open and curious among them (a more developed frontal cortex?) are listening attentively. Can the days when vexing issues, such as religion and faith in a higher being, find a biological explanation be far off? Is conflict resolution between individuals and nations amenable to biological treatment? Science is what we make it to be. If we put it to good use, it can promise humanity.