The Biology of Right and Wrong
PHILOSOPHERS have long debated the foundations of moral decision-making. “Rationalists” from Socrates to Immanuel Kant argued that people should rely on intellect when distinguishing right from wrong. “Sentimentalists” like David Hume believed the opposite: emotions such as empathy should guide moral decisions.
Now Hazel associate professor of the social sciences Joshua Greene, a philosopher, experimental psychologist, and neuroscientist, is trying to resolve this dispute by combining brain-scanning technology with classic experiments from moral psychology to provide a new look at how rationality and emotion influence moral choices. His work has led him to conclude that “emotion and reason both play critical roles in moral judgment and that their respective influences have been widely misunderstood.”
Greene’s “dual-process theory” of moral decision-making posits that rationality and emotion are recruited according to the circumstances, with each offering its own advantages and disadvantages. He likens the moral brain to a camera that comes with manufactured presets, such as “portrait” or “landscape,” along with a manual mode that requires photographers to make adjustments on their own. Emotional responses, which are influenced by humans’ biological makeup and social experiences, are like the presets: fast and efficient, but also mindless and inflexible. Rationality is like manual mode: adaptable to all kinds of unique scenarios, but time-consuming and cumbersome.
“The nice thing about the overall design of the camera is that it gives you the best of both worlds: efficiency in point-and-shoot mechanisms and flexibility in manual mode,” Greene explains. “The trick is to know when to point and shoot and when to use manual mode. I think that this basic design is really the design of the human brain.”
Unlike earlier philosophers, he can test his theories with neuroscientific instruments. His primary tool is functional magnetic resonance imaging (fMRI), which takes advantage of the fact that many mental functions are localized to specific areas of the brain. Deliberative reasoning, for instance, is housed in the prefrontal cortex, whereas the amygdala is considered the seat of the emotions. By monitoring blood flow to these areas, fMRI allows Greene and his colleagues to observe exactly when someone is relying on “manual mode” or “automatic settings.”