Another way to study moral intuition is to look at brains that lack it. James Blair at the National Institute of Mental Health has spent years performing psychological tests on criminal psychopaths. He has found that they have some puzzling gaps in perception. They can put themselves inside the heads of other people, for example, acknowledging that others feel fear or sadness. But they have a hard time recognizing fear or sadness, either on people’s faces or in their voices.
Blair says that the roots of criminal psychopathy can first be seen in childhood. An abnormal level of neurotransmitters might make children less empathetic. When most children see others get sad or angry, it disturbs them and makes them want to avoid acting in ways that provoke such reactions. But budding psychopaths don’t perceive other people’s pain, so they don’t learn to rein in their violent outbreaks.
As Greene’s database grows, he can see more clearly how the brain’s intuitive and reasoning networks are activated. In most cases, one dominates the other. Sometimes, though, they produce opposite responses of equal strength, and the brain has difficulty choosing between them. Part of the evidence for this lies in the time it takes for Greene’s volunteers to answer his questions. Impersonal moral ones and nonmoral ones tend to take about the same time to answer. But when people decide that personally hurting or killing someone is appropriate, it takes them a long time to say yes—twice as long as saying no to these particular kinds of questions. The brain’s emotional network says no, Greene’s brain scans show, and its reasoning network says yes.
When two areas of the brain come into conflict, researchers have found, an area known as the anterior cingulate cortex, or ACC, switches on to mediate between them. Psychologists can trigger the ACC with a simple game called the Stroop test, in which people have to name the color of a word. If subjects are shown the word blue in red letters, for instance, their responses slow down and the ACC lights up. “It’s the area of the brain that says, ‘Hey, we’ve got a problem here,’” Greene says.
Greene’s questions, it turns out, pose a sort of moral Stroop test. In cases where people take a long time to answer agonizing personal moral questions, the ACC becomes active. “We predicted that we’d see this, and that’s what we got,” he says. Greene, in other words, may be exposing the biology of moral anguish.
Of course, not all people feel the same sort of moral anguish. Nor do they all answer Greene’s questions the same way. Some aren’t willing to push a man over a bridge, but others are. Greene nicknames these two types the Kantians and the utilitarians. As he takes more scans, he hopes to find patterns of brain activity that are unique to each group. “This is what I’ve wanted to get at from the beginning,” Greene says, “to understand what makes some people do some things and other people do other things.”
Greene knows that his results can be disturbing: “People sometimes say to me, ‘If everyone believed what you say, the whole world would fall apart.’” If right and wrong are nothing more than the instinctive firing of neurons, why bother being good? But Greene insists the evidence coming from neuroimaging can’t be ignored. “Once you understand someone’s behavior on a sufficiently mechanical level, it’s very hard to look at them as evil,” he says. “You can look at them as dangerous; you can pity them. But evil doesn’t exist on a neuronal level.”
By the time Patel emerges from the scanner, rubbing his eyes, it’s past 11 p.m. “I can try to print a copy of your brain now or e-mail it to you later,” Greene says. Patel looks at the image on the computer screen and decides to pass. “This doesn’t feel like you?” Greene says with a sly smile. “You’re not going to send this to your mom?”
Soon Greene and Patel, who is Indian, are talking about whether Indians and Americans might answer some moral questions differently. All human societies share certain moral universals, such as fairness and sympathy. But Greene argues that different cultures produce different kinds of moral intuition and different kinds of brains. Indian morality, for instance, focuses more on matters of purity, whereas American morality focuses on individual autonomy. Researchers such as Jonathan Haidt, a psychologist at the University of Virginia, suggest that such differences shape a child’s brain at a relatively early age. By the time we become adults, we’re wired with emotional responses that guide our judgments for the rest of our lives.
Many of the world’s great conflicts may be rooted in such neuronal differences, Greene says, which may explain why the conflicts seem so intractable. “We have people who are talking past each other, thinking the other people are either incredibly dumb or willfully blind to what’s right in front of them,” Greene says. “It’s not just that people disagree; it’s that they have a hard time imagining how anyone could disagree on this point that seems so obvious.” Some people wonder how anyone could possibly tolerate abortion. Others wonder how women could possibly go out in public without covering their faces. The answer may be that their brains simply don’t work the same: Genes, culture, and personal experience have wired their moral circuitry in different patterns.
Greene hopes that research on the brain’s moral circuitry may ultimately help resolve some of these seemingly irresolvable disputes. “When you have this understanding, you have a bit of distance between yourself and your gut reaction,” he says. “You may not abandon your core values, but it makes you a more reasonable person. Instead of saying, ‘I am right, and you are just nuts,’ you say, ‘This is what I care about, and we have a conflict of interest we have to work around.’”
Greene could go on—that’s what philosophers do—but he needs to switch back to being a neuroscientist. It’s already late, and Patel’s brain will take hours to decode.