Our modern powers of self-control are the product of long-ago pressures to be better neighbours, parents, and mates. But how exactly did the human brain catch up? The answer appears to be the development of the prefrontal cortex, a nice chunk of neural real estate right behind your forehead and eyes. For most of evolutionary history, the prefrontal cortex mainly controlled physical movement: walking, running, reaching, pushing—a kind of proto-self-control.
As humans evolved, the prefrontal cortex got bigger and better connected to other areas of the brain. It now takes up a larger portion of the human brain than in the brains of other species—one reason you’ll never see your dog saving kibble for retirement. As the prefrontal cortex grew, it took on new control functions: controlling what you pay attention to, what you think about, even how you feel. This made it even better at controlling what you do. Robert Sapolsky, a neurobiologist at Stanford University, has argued that the main job of the modern prefrontal cortex is to bias the brain—and therefore, you—toward doing “the harder thing.” When it’s easier to stay on the couch, your prefrontal cortex makes you want to get up and exercise.
When it’s easier to say yes to dessert, your prefrontal cortex remembers the reasons for ordering tea instead. And when it’s easier to put that project off until tomorrow, it’s your prefrontal cortex that helps you open the file and make progress anyway.
The prefrontal cortex is not one unified blob of gray matter; it has three key regions that divvy up the jobs of I will, I won’t, and I want. One region, near the upper left side of the prefrontal cortex, specializes in “I will” power. It helps you start and stick to boring, difficult, or stressful tasks, like staying on the treadmill when you’d rather hit the shower. The right side, in contrast, handles “I won’t” power, holding you back from following every impulse or craving. You can thank this region for the last time you were tempted to read a text message while driving but kept your eyes on the road instead. Together, these two areas control what you do.
The third region, just a bit lower and in the middle of the prefrontal cortex,
keep track of your goals and your desires. It decides what you want. The
more rapidly its cells fire, the more motivated you are to take action or resist
temptation. This part of the prefrontal cortex remembers what you really
want, even when the rest of your brain is screaming, “Eat that! Drink that!
Smoke that! Buy that!”
UNDER THE MICROSCOPE: WHAT IS THE HARDER THING?
Every willpower challenge requires doing something difficult, whether it’s walking away from temptation or not running away from a stressful situation. Imagine yourself facing your specific willpower challenge. What is the harder thing? What makes it so difficult? How do you feel when you think about doing it?
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