We humans like to think that we have much more self-discipline than other animals. We know how to set goals—losing 25 pounds, starting our own businesses—and then we resist temptations and slog through difficulties to achieve them. We are far from perfect at this talent, but in most of our minds there is no question that our powerful self-control is one of the things that sets us apart from more lowly beasts.
Scientists have long argued that delaying gratification requires a sense of “self.” Having a personal identity allows us to compare who we are today, at this very moment, with who we want to be—an idealized self. Such aspirations are thought to foster the kind of behavior that leads to self-improvement. But new research suggests a more primitive source of our powers of self-discipline. It appears that, lofty as our goals may be, we rely on the same basic biological mechanism for self-discipline as our four-legged best friends.
Sit. Now Stay.
Experimental psychologist Holly Miller and her colleagues at the University of Kentucky knew from previous research that in people, self-control relies on the brain’s “executive” powers, which coordinate planning and action. It is further known that this kind of effortful cognitive processing requires energy in the form of glucose, the simple sugar that serves as the body’s fuel. Studies show that depletion of the brain’s glucose supply compromises self-discipline. For instance, passing up a tempting happy-hour drink after work may make it tougher to forgo your favorite television show later on that evening to exercise. Of course, all mental activities require energy, but self-control seems to be one process that is especially compromised when the energy starts running out. But is this a uniquely human phenomenon?