So many acts in our daily lives – refusing that second slice of cake, walking past the store with the latest gadgets, working on your tax forms when you’d rather watch TV – seem to boil down to one essential ingredient: self-control. Self-control is what enables us to maintain healthy habits, save for a rainy day, and get important things done.

But what is self-control, really? And how does it work?

In a new article in the September 2012 issue of Perspectives on Psychological Science, a journal of the Association for Psychological Science, researchers Michael Inzlicht of the University of Toronto and Brandon Schmeichel of Texas A&M University argue that the prevailing model of self-control may not be as precise as researchers once thought. Rather than being a limited resource, self-control may actually be more like a motivation- and attention-driven process.

Research on self-control has surged in the last decade and much of it has centered on the resource model of self-control. According to this model, originally proposed by Roy Baumeister and colleagues, self-control is a limited resource – if we exercise a lot of self-control by refusing a second slice of cake, we may not have enough self-control later in the day to resist the urge to shop or watch TV.

Over 100 papers have produced findings that support this model. Research has found, for example, that people who are required to manage their emotions show impaired performance on later tasks, such as solving a difficult puzzle, squeezing a handgrip exerciser, and keeping items in working memory.

But Inzlicht and Schmeichel point out that a newer crop of studies are yielding results that don’t fit with this idea of self-control as a depletable resource. Recent studies have shown that incentives, individual perceptions of task difficulty, personal beliefs about willpower, feedback on task performance, and changes in mood all seem to influence our ability to exercise self-control. These results suggest that self-control may not rely on a limited resource after all.

To accommodate these new findings and get at the mechanisms that underlie self-control, Inzlicht and Schmeichel propose an alternative model that describes self-control as a process involving motivation and attention.

“Engaging in self-control by definition, is hard work; it involves deliberation, attention, and vigilance,” the authors write. If we resist that second slice of cake, we may experience a shift in motivation so that we feel justified in indulging ourselves later on. It’s not necessarily the case that we can’t control ourselves because we’re “out” of self-control but rather that we choose not to control ourselves any longer.

At the same time, our attention shifts so that we’re less likely to notice cues that signal the need for self-control (cake = empty calories) and we pay more attention to cues that signal some kind of reward (cake = delicious treat).

In laying out the basic components of this process model, Inzlicht and Schmeichel want to motivate researchers to ask critical questions about how self-control really works. “The idea that self-control is a resource is one possibility, but there are alternative possibilities that can accommodate more of the accumulated data,” Inzlicht says.

Identifying the mechanisms that underlie self-control can help us to understand behaviors related to a wide range of important problems, including obesity, impulsive spending, gambling, and drug abuse. Inzlicht and Schmeichel hope that researchers will ultimately be able to use this knowledge to design effective methods for improving self-control.