Self-control, also known as willpower, is an essential ability. It allows us to override our direct temptations, so we could focus on other ambitions. The lack of self-control caused, and still causes, many woes in human society. Therefore, it is important for social sciences to study this phenomenon.

A central role in the theory of self-control is formed by the existence of an energy resource in the self. Self-controlling acts draw on this energy source, causing depletion. This state of mental exhaustion is called ego depletion and has played a central role in many studies. Because of the diminished energy resources, ego depletion leads to decreased abilities to control oneself.

What is ego depletion?

The article presents an alternate model that could help explain why an act of self-control at one time causes impairments on other self-controlling tasks at a time afterwards. The authors of the article propose that self-controlling behavior leads to shifts in both attentional focus and motivational orientation. Those two processes are interrelated an can be seen as two meshed gears: because the motivation shifts from controlling behavior to impulsive acts of behavior, the attentional focus will change. Thus, ego depletion is not the mysterious result of energy resource depletion: it is simply a shift in motivation and attention.

Research on ego-depletion states that the self has a limited resource of energy, out of which self-controlling behaviors draw their energy. But, what is that exact resource? Studies from Gailliot, Baumeister, and colleagues showed that acts of self-control consume glucose, and that a state of ego-depletion can be cured by drops of glucose. In that way, the mysterious energy resource could just be a metaphor for blood glucose levels. However, the glucose findings are controversial: the studies could not prove that acts of self-control do not reliably reduce glucose levels in the blood. There may be a link between those two, but the relationship is probably more complex than the study outcomes imply.

Other studies also challenged the resource model. A study by Muraven and Slessareva showed that ego depletion is more a motivational deficit rather than a resource deficit; research by Clarkson, Hirt, Jia, and Alexander showed that ego depletion may be more driven by subjective perceptions rather than by a diminished energy resource. Studies by Tice, Baumeister, Shmueli and Muraven had the outcome that positive affects could have influence on the level of ego depletion.

The mechanistic model of ego depletion

Although the existence of an energy resource may be a myth, the question what makes self-control limited hasn’t been answered. As mentioned before, two processes play a central role in causing ego depletion, respectively motivation and attention.

The process of motivation can be split in two separate processes. The first one is the will to control oneself. Self-control can require hard work, and after the job is done, people may feel that they owe a break. In other words, they are not motivated to regulate themselves anymore. This vision is consistent with the before-mentioned glucose theory and many studies had outcomes that supported this idea of motivation. However, those studies did not adequately distinguish a lack of willpower and a lack of ability. More research needs to be done to find out if depletion is really an effect of diminished motivation.

Not only the level of motivation is important: after one’s become ego-depleted, he or she will be stronger inclined to act on impulse. Studies find that acts of self-control lead to more approach-motivated impulse strength. But once again, more research is required.

The process of attention can also be split in two apart processes. The fist one concerns the need that someone feels to control himself. Self-control may fail in cases people don’t notice they have to control themselves. Cybernetic loop models can help to explain this process: they explain control with three components, namely goals or standards, comparators or monitors and effectors or operators. According to this theories, self-control may fail as a result of problems with the operators of control, missing the ability to regulate oneself. It can also fail due to problems with monitoring: in that case, people don’t have the insight of discrepancies between their goal state and their current state. Studies show that participants who exert self-control, have more difficulty with attentional control in further tasks that require self-control. The other attentional process mentioned is the possibility of rewards. When depleted, people tend to focus on rewards and pleasure. This is caused by motivation systems, like the behavioral activation system, the fight-or-flight system and the behavioral inhibition system.

As mentioned before, the processes motivation and attention interact. Shifts in motivation lead to shifts in attention; the reverse is also possible. If people don’t recognize the cues for the need to control themselves, they will focus more on rewards: their attention will shift away from control and towards the gratification of impulses.

The mechanistic model integrated with other models

Though the process model isn’t in line with the common used resource model, it sure align with other theories. One of these theories is the attentional myopia model of self-control by Mann and Ward. According to this model, failing self-control could be the result of a too strong focus on central cues, instead of more peripheral. This is in line with the processes of attentional shift and the focus on rewards that play a central role in the process model. Another model comes from research by Kivetz, Simonson, Mukhopadhyay and Johar. Their studies suggest that self-control fails because people don’t want to control themselves, rather than just lacking abilities to regulate themselves. Again, there are similarities with the motivational process from the process model.