A great deal of recent research (some of which I've written about in this blog) suggests that our capacity for is much like a muscle. Its strength varies from person to person, and also from moment to moment, depending on how recently and how hard it's had to work. (Think about how your legs can feel like jelly after a long run, and you get the idea.)



Just as our muscle strength is inherently limited, so too are our reserves of willpower. Thus, self-control is often at its weakest immediately after we've had to use it - an effect demonstrated in dozens of published studies, and obvious to anyone who has every succumbed to the urge to drink, smoke, or eat a whole pint of ice cream at the end of very day.



But what if you happened to be someone who believed that engaging in difficult tasks was energizing, rather than depleting? What if you were convinced that using your willpower activates resources, rather than drains them? What would happen?



You'd be right! Thanks to a new set of studies by Veronika Job, Carol Dweck, and Gregory Walton, it's become clear that people's beliefs about the nature of self-control determine whether or not it is depleted by use.



The researchers distinguished between people who believed that willpower is a limited resource or a non-limited resource, and found that only those who believed in the limited-resource theory had less self-control (i.e., made lots of mistakes) after working on something very difficult.



How can this be? Both groups were equally exhausted by difficult task, so you might think they would be equally mistake-prone. But it turns out that our theories about self-control determine how exhaustion affects us.



When people who hold the limited-resource view experience something as exhausting, they have less self-control and are more prone to errors because they see exhaustion as a sign to reduce effort, in order to rest and eventually replenish their self-control reserves. In contrast, those with the non-limited resource view continue to put in effort despite their exhaustion, and make fewer errors because of it.



These beliefs, not surprisingly, predict how people handle the more stressful and demanding periods in their lives. For instance, the researchers found that during the more stressful, exam-filled weeks in the academic semester, belief in the limited-resource theory of self-control predicted greater consumption of unhealthy junk foods, , and less effective study habits among college students. Those who believed in limitless willpower, on the other hand, held up under stress just fine.



So, is self-control limited, or isn't it? The answer has become a lot less clear, and frankly, I'm no longer sure it matters. What does matter is whether or not you believe that it's limited. And since you have some choice when it comes to your beliefs, I recommend going with the limitless willpower view. Maybe in the end, all it takes to put down that pint of ice cream at the end of the day is believing that you actually can.