Willpower, Diet Coke, and Buddha

Sixteen years ago I quit smoking. It was one of the hardest things I have ever done. For weeks and months during this time I had to exert constant self-control over the urge to resume the habit. A lot of this effort involved being vigilant to events and situations that used to automatically trigger smoking and then willfully blocking the urge to light up a cigarette. It was also necessary to exert control over an emotional response that was evoked by not having access to cigarettes -- a feeling of panic that non-smokers probably can't relate to at all. During this period I was irritable, of course, but also often forgetful, distracted, and downright muddled (even more than usual).

Social Psychologists have focused a great deal of research on the mechanisms of self-control and the consequences of exerting this kind of cognitive effort. Examples of behaviors that have been studied in this context include managing the impression we think we are making on others, suppressing our prejudices and stereotypes, coping with fear of dying, controlling our spending, holding back aggression, and limiting the amount of food or alcohol we ingest (see Galliot et. al, 2007 for references).

A consistent finding in these studies is that self control is a depletable resource. The prominent social psychologist Roy Baumeister summarized this research as follows: "...self-control appear[s] vulnerable to deterioration over time from repeated exertions, resembling a muscle that gets tired. The implication [is] that effortful self-regulation depends on a limited resource that becomes depleted by any acts of self-control, causing subsequent performance even on other self-control tasks to become worse" (Baumeister et. al, 2007). For example, in one study people who exerted self control by eating healthy vegetables instead of more temping chocolate candy and cookies gave up faster on a subsequent frustrating task as compared to people who had not exerted self-control. This depletion phenomenon would certainly account for my irritability and befuddlement during my struggle to quit smoking -- my mind muscle was pooped.

It isn't necessary to invoke a new-agey concept of "psychic energy" to account for these data. The cognitive activity involved in self-control is firmly tied to physiological processes in the brain -- an organ that uses 20% of the body's calories and yet has just 2% of its mass. A major source of energy for the brain is glucose, or blood sugar, which is converted to neurotransmitter chemicals that fuel the brain. A series of recent experiments by Gailliot et. al. (2007) have demonstrated that exerting self control depletes glucose, whereas other kinds of cognitive activity that are more automatic do not, and that lowered levels of glucose result in impaired self control on subsequent tasks. Increasing glucose levels, either by allowing them to rebound naturally or by ingesting glucose rich drinks, was found to restore performance on self-control tasks. An ironic implication of this (untested, as far as I know) is that dieters who drink artificially sweetened soda may lower their blood sugar level and thus may make it harder for themselves to stick to their weight-loss diets.

What I have outlined here is called the Strength Model of Self-Control, and it clearly has a great deal of empirical support. For me the most important thing in the model is not just that self-control or willpower is a depletable resource, but rather that there are ways of developing greater self-control such that depletion is lessened -- an extension of the "muscle" analogy suggested by Baumeister. Research has indicated that...

"...just as exercise can make muscles stronger, there are signs that regular exertions of self-control can improve willpower strength... These improvements typically take the form of resistance to depletion, in the sense that performance at self-control tasks deteriorates at a slower rate. Targeted efforts to control behavior in one area, such as spending money or exercise, lead to improvements in unrelated areas, such as studying or household chores. And daily exercises in self-control, such as improving posture, altering verbal behavior, and using one’s nondominant hand for simple tasks, gradually produce improvements in self-control as measured by laboratory tasks. The finding that these improvements carry over into tasks vastly different from the daily exercises shows that the improvements are
not due to simply increasing skill or acquiring self-efficacy from practice." (Baumeister et. al., 2007)

There are other ways of improving self-control not mentioned by Baumeister, including techniques offered by some religious traditions, such as Buddhism, which stresses the development of self control over one's thoughts, perceptions, and emotions through meditation. Whatever the technique, the positive implication is clear: self-control "...appears to facilitate success in life in many spheres, and, crucially, it appears amenable to improvement. Indeed, self-control can be grouped with intelligence among the (rather few) traits that are known to contribute to success in human life across a broad variety of spheres; yet unlike intelligence,
self-control appears amenable to improvement from psychological interventions, even in adulthood" (Baumeister et. al., 2007)


References

Baumeister, R. F., Bratslavsky, E., Vohs, Kathleen D., & Tice, D. M. (2007). The Strength Model of Self-Control. Current Directions in Psychological Science, 16 (6): 351-355.

Gailliot, M.T., Baumeister, R.F., DeWall, C.N., Maner, J.K., Plant, E.A., & Tice, D.M., et al. (2007). Self-control relies on glucose as a limited energy source: Willpower is more than a metaphor. Journal of Personality and Social Psychology, 92, 325–336.