Making Major Moral Decisions

Joshua Greene, a psychologist at Harvard University, believes “moral judgment is just a brain process.” When we’re faced with uncertainty in a moral decision, he says, distinct brain regions keep track of the two kinds of information we consider—the magnitude of a choice (how good or bad the possible outcomes are) and the probabilities those outcomes will occur based on our choice. But where do these pieces of information get integrated?

To find out, Greene and doctoral student Amitai Shenhav scanned the brains of a group of volunteers as they decided which of two options to choose: successfully save the life of one person or try to save the lives of several people even though there was no guarantee of actually saving any of them. The researchers did the experiment a number of times, varying the lives at risk and the odds of success.

The brain scans appear to show that regions called the “ventromedial prefrontal cortex” and “ventral striatum” tracked the expected number of lives saved or lost—or the the “expected moral value”—of each uncertain option by integrating how many lives could be saved (the magnitude) with the chances of saving them (the probability).

And Greene points out something fascinating:

Our work shows that the parts of the brain people use for this last task—combining assessments of outcome probability and magnitude into a final decision—closely coincide with the brain regions we use daily when deciding how to spend money or choose foods.

In other words, the researchers write, the “complex life-and-death moral decisions that affect others depend on neural circuitry adapted for more basic, self-interested decision making involving material rewards.”