Why do some people effortlessly resist that second cupcake while others struggle to say no? According to psychologist Kelly McGonigal, willpower isn’t just about resisting temptation—it’s about choosing the harder option. The secret lies in your brain’s prefrontal cortex, which acts as your willpower control center.
This guide explores the neuroscience behind self-control, drawing on insights from McGonigal’s The Willpower Instinct and Baumeister and Tierney’s Willpower. You’ll learn how your brain’s structure affects your self-control, why glucose levels matter for mental stamina, and what evolutionary pressures shaped our modern willpower systems.
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The Psychology of Willpower
In her book The Willpower Instinct, Kelly McGonigal says that most people think of willpower or self-control as the ability to resist temptation. When we say, “I have no willpower,” we mean we can’t say no to ourselves. We believe we can’t eat just one potato chip; we will eat the entire bag. We believe we can’t pull ourselves away from the couch and Netflix, even when we know it’s time to go to the gym.
Saying “no” to our impulses is just half of the willpower equation. We need to be able to say “no” to some things (perhaps that third glass of wine or second cupcake) and “yes” to others (maybe working out, going to bed earlier, or eating more broccoli). Whether it’s a “yes” or a “no,” willpower usually involves choosing the more difficult of two options. Accessing your willpower means opting for the harder choice instead of giving in to what seems alluring in the present moment.
How Our Willpower Evolved
You might think the need for willpower is a modern invention, but even our Stone Age ancestors required it. Not only were they tasked with finding food and avoiding large predators, but they also had to cultivate the skills to live successfully in tight-knit tribes. Since they weren’t well equipped to survive on their own, they had to be good neighbors, parents, and mates—which meant they required willpower to control their impulses. Possessing strong self-control allowed them to share food, cooperate, and collaborate with each other for hunting and protection. It also helped them choose suitable mates for reproduction.
As time went on, human societies became larger and more complex, and self-control became even more important. Our brains had to develop a more sophisticated self-control system to adapt to more complicated social circumstances. The brain’s prefrontal cortex began to evolve, growing larger and more closely connected to other brain regions.
Today, humans have a larger prefrontal cortex—relative to our brain size—than any other species. It controls much of what we pay attention to, think about, feel, and do.
Prefrontal Cortex: Willpower Control Center
As with other human traits, some people have a bigger, better-developed prefrontal cortex than others, which makes a difference in their behaviors. When people with a larger prefrontal cortex think of saying yes to a second helping of dessert, their brains remind them that this is a bad idea, and they say no instead. When they want to go to the beach instead of studying for final exams, their prefrontal cortex reminds them that only A-plus grades will get them into medical school.
It may not seem fair, but people with a larger prefrontal cortex usually have more willpower, and as a result, they lead easier lives.
The research: Studies have shown that self-control is more important than IQ scores in predicting academic success. And the benefits don’t stop there: People with a larger prefrontal cortex tend to make more money, go further in their careers, have longer-lasting relationships, and so on.
How the Prefrontal Cortex Works
The prefrontal cortex has different regions that perform the three functions of willpower. You considered these three functions—I will, I won’t, and I want—when you chose your Personal Willpower Challenge. Each region plays a role in protecting us from our impulsive desires. The left side handles “I will.” The right side handles “I won’t.” The lower middle portion keeps a record of long-term goals and desires. The faster and more efficiently each region functions, the more reliable your willpower will be.
To illustrate how critical the prefrontal cortex is, consider the story of Phineas Gage, an American railroad foreman in 1848. Gage was involved in a terrible explosion that shattered his skull and blew out parts of his brain, but somehow he survived. Doctors patched up his head, and in a few months the outer skin healed. But because Gage’s prefrontal cortex was missing, his personality was completely altered. Before the accident, he was quiet, gentle, respectful, and “possessing an iron will.” After the accident, he was mean, impulsive, and behaved “with animal propensities.”
Most of us will never suffer this kind of disability, but we’ve all put ourselves in situations where our prefrontal cortexes are compromised. If we’re tired, drunk, or even just distracted, the prefrontal cortex can’t do its job efficiently. That means we won’t be able to access our willpower, and we’ll be more likely to give in to impulse.
| Unraveling the Science of Willpower On an episode of the podcast Huberman Lab, Andrew Huberman touched on the science of willpower, especially the anterior mid-cingulate cortex (aMCC) and glucose consumption. The Role of the Anterior Mid-Cingulate Cortex: The aMCC is a key region in the brain that integrates internal and external information. Confronting obstacles significantly activates the aMCC, underscoring its central role in self-control and resilience. Operating as a hub influenced by inputs related to various cognitive functions, the aMCC enhances our willpower when it’s needed most. Huberman spotlights how the aMCC modulates motivation and behavior critical for achievement and self-discipline. By shedding light on the aMCC’s function, the podcast episode provides insight into the neural underpinnings of perseverance in the face of challenge. |
The Duality of Our Brains
Some scientists say we have “one brain but two minds.” One mind caters to immediate gratification. The other mind delays gratification in the interest of long-term goals. We’re conflicted because we want two competing rewards—the 30-second happiness of eating a cupcake and the longer-term happiness of a healthy, trim physique. We know we can’t have both, but that doesn’t stop us from wanting both.
Willpower As a Form of Energy
In their book Willpower, Roy F. Baumeister and John Tierney begin by saying that willpower isn’t merely an abstract idea, but a real force like physical strength.
Just like you use your muscles to accomplish physically challenging tasks, you use willpower to accomplish mentally taxing tasks—for instance, resisting temptations and staying focused on challenging or tedious work. Willpower also helps you to maintain your self-control in difficult or upsetting situations, such as emergencies and arguments.
(Shortform note: The scientific definition of energy is simply the ability to do work. So, for instance, when you use your muscles to move something heavy, you’re exerting kinetic energy. The authors are taking some artistic license in saying that willpower is a similar form of energy—there’s no way to directly observe the effects of willpower, like you could observe a piece of furniture moving as you push it—but they say this to emphasize that willpower is the ability to do mental work.)
Glucose Is Your (Will)Power Source
Baumeister and Tierney explain that willpower, like everything else in your body, relies on glucose as its primary energy source. This means that your ability to exercise self-control is directly linked to your glucose levels. This fact has profound implications for how your physical health and your eating habits can impact your willpower.
(Shortform note: Glucose is a simple sugar molecule. It serves as the fundamental fuel that powers life across nearly all of Earth’s organisms, not just humans. Through processes like photosynthesis in plants and digestion in animals, complex carbohydrates are broken down into glucose. Cells then use cellular respiration to metabolize glucose into ATP (adenosine triphosphate), a molecule for storing and releasing energy, which drives everything from muscle contraction to nerve signaling.)
According to the authors, research has shown that willpower-intensive tasks, like staying focused for extended periods of time at work, deplete your glucose reserves just like physical exercise does. That’s why, for instance, people tend to get more irritable and impulsive when they’re hungry: Their glucose levels are low, and therefore their self-control is impaired.
However, this connection also means that you can replenish your willpower by consuming food or drinks that boost your glucose levels. It might be tempting to go for sugary, processed foods like candy and soda, but the authors say that such foods only give you short bursts of energy, followed by crashes when your blood sugar drops again. Healthier choices such as fruits and whole grains will create a more stable and sustained release of glucose, providing reliable and long-lasting fuel for your willpower.
(Shortform note: You can check how much energy a particular food will give you by looking up its glycemic index (GI). The GI is a measurement system that ranks foods based on how quickly they raise blood sugar levels. Scores range from zero (no glucose) to 100 (pure glucose). As the authors state, it’s generally better to eat foods with low GI scores, because those tend to provide reliable long-term energy rather than a quick spike in blood sugar. Low GI foods include non-starchy vegetables like carrots and broccoli, as well as legumes such as beans. On the other hand, most kinds of bread, white rice, starchy vegetables like potatoes, and anything with added sugar are considered high GI foods, and should be eaten in moderation.)
Learn More About Willpower
If you found this article interesting and want to learn more about willpower, check out the full guides to the books mentioned here:
