A group of scientists at the California Institute of Technology decided to see what they could learn about self-control and how it works by testing a bunch of volunteers who were on a diet. The researchers asked the dieters to choose between different foods and found that some of them showed enormous self-control, almost always picking a healthy food regardless of taste. Others, though, showed very little self-control, almost always choosing the food they thought tasted better regardless of its nutritional value. The researchers then looked at brain scans taken while the dieters made their choices.
"A very basic question in economics, psychology, and even religion, is why some people can exercise self-control but others cannot," says Antonio Rangel, a professor of economics at Caltech who worked on the study. "From the perspective of modern neuroscience, the question becomes, 'What is special about the circuitry of brains that can exercise good behavioral self-control?'"
If the researchers are right, the brains of people who have strong self-control are different from the brains of those who have weaker willpower. We all use the same area of the brain to make value-based decisions about things like what to eat, they say, and the more activity this brain region shows in response to a certain food, the more likely we are to choose that food.
In dieters with low self-control, this brain area shows activity in response to the taste of food alone. In dieters with strong self-control, however, a second brain region modulates the activity of the first—and, as a result, these people can weigh not only basic desires (like taste) but also more abstract factors (like healthiness) when making a decision.
"We rarely got people to say they'd eat cauliflower if they didn't like cauliflower," says Todd Hare, a postdoc in neuroeconomics who also worked on the study. "But they would choose not to eat ice cream or candy bars, knowing they could eat the healthier index food instead." —Heather Wax