The Neuroscience of Morality

Responsibility is both scientific and moral
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Nov 30, 2010

A longer version of this discussion appears at the Kenan Institute for Ethics as part of its "Good Question" series.

If a brain tumor leads a father to molest his daughter (an actual case), can he be held morally or legally responsible for his actions?

In this unusual case, a 40-year-old Virginia father and teacher led a fairly normal sex life until 2000, when he began collecting pornography, then child pornography, and finally he propositioned his stepdaughter. After being convicted of child molestation, he began experiencing headaches and a loss of coordination, leading to a diagnosis of a brain tumor. When the tumor was removed, his problematic behaviors and desires disappeared. He was eventually allowed to go home to his family. Several months later, the tumor returned, and so did his unusual behavior, before the tumor was removed again. 

Duke Philosopher Walter Sinnott-Armstrong, the Chauncey Stillman Professor in Practical Ethics, often compares morality with jade: “Most people think of it as a single mineral, but there are actually two types of jade, with different chemical compositions. They only appear to be the same,” he says.

“We make the same mistake when we think about morality. We assume that a single term, ‘morality,’ can be used to describe all types of moral judgments, but judgments about fairness, harm, justice, honesty, responsibility, or sex are so varied that it’s a vast oversimplification to think of them as some larger unitary ‘thing’ called morality.”

Because of his brain tumor, "many people conclude that (the Virginia man) was not fully responsible for his misconduct. I agree, but this judgment creates a conflict," Sinnott-Armstrong says.
"All desires and actions are driven by various brain processes. Why is an individual responsible when a “normal” brain condition causes an act but not when a tumor causes an act?" Sinnott-Armstrong addresses these questions by using the tools of neuroscience. He has compared this brain tumor case to other conditions, including Tourette syndrome, alien hand syndrome, addiction, psychopathy, and other mental illnesses, with a goal of gaining a better understanding of "responsibility."

Functional magnetic resonance imaging (fMRI) locates brain activity by measuring changes in blood flow, making it possible to infer which parts of the brain are engaged when people make different types of moral judgments.

Findings suggest that different kinds of moral judgments -- about harm as opposed to “impure” sex, for example -- are related to different parts of the brain.

Different cognitive functions and different brain mechanisms are involved when people make a moral judgment of an act causing harm (for example, a murder or theft) than when they judge an act seen as “impure” but harmless (such as special cases of cannibalism or consensual incest) or dishonest but harmless (such as some lies or broken promises).

“All of these acts are sometimes called ‘immoral,’” Sinnott-Armstrong says, “but at the basic physical level, morality is even less unified than jade.”

"Complicating the issue is the role of conscious will and its bearing on responsibility," he adds. "In both law and morals, we normally excuse people whose acts are not caused by their conscious choices, such as sleepwalkers. The question is whether the excuse granted to sleepwalkers really applies to us all more often than we think.

Surprisingly, recent research suggests that conscious choice plays a smaller role in our actions than most people assume. In particular, it often comes after brain activity that initiates bodily movements, and many researchers conclude that the conscious choice does not cause the movement. That conclusion raises the disturbing questions of whether and how we can ever really be responsible for anything."

"In the end, the issue of responsibility is both scientific and moral," Sinnott-Armstrong says. "To answer the crucial questions, neuroscientists and philosophers must work together."