No abstract

Much recent research suggests that willpower--the capacity to exert self-control--is a limited resource that is depleted after exertion. We propose that whether depletion takes place or not depends on a person's belief about whether willpower is a limited resource. Study 1 found that individual differences in lay theories about willpower moderate ego-depletion effects: People who viewed the capacity for self-control as not limited did not show diminished self-control after a depleting experience. Study 2 replicated the effect, manipulating lay theories about willpower. Study 3 addressed questions about the mechanism underlying the effect. Study 4, a longitudinal field study, found that theories about willpower predict change in eating behavior, procrastination, and self-regulated goal striving in depleting circumstances. Taken together, the findings suggest that reduced self-control after a depleting task or during demanding periods may reflect people's beliefs about the availability of willpower rather than true resource depletion.

Laboratory research shows that when people believe that willpower is an abundant (rather than highly limited) resource they exhibit better self-control after demanding tasks. However, some have questioned whether this "nonlimited" theory leads to squandering of resources and worse outcomes in everyday life when demands on self-regulation are high. To examine this, we conducted a longitudinal study, assessing students' theories about willpower and tracking their self-regulation and academic performance. As hypothesized, a nonlimited theory predicted better self-regulation (better time management and less procrastination, unhealthy eating, and impulsive spending) for students who faced high self-regulatory demands. Moreover, among students taking a heavy course load, those with a nonlimited theory earned higher grades, which was mediated by less procrastination. These findings contradict the idea that a limited theory helps people allocate their resources more effectively; instead, it is people with the nonlimited theory who self-regulate well in the face of high demands.

Self-control is positively associated with a host of beneficial outcomes. Therefore, psychological interventions that reliably improve self-control are of great societal value. A prominent idea suggests that training self-control by repeatedly overriding dominant responses should lead to broad improvements in self-control over time. Here, we conducted a random-effects meta-analysis based on robust variance estimation of the published and unpublished literature on self-control training effects. Results based on 33 studies and 158 effect sizes revealed a small-to-medium effect of g = 0.30, confidence interval (CI) [0.17, 0.42]. Moderator analyses found that training effects tended to be larger for (a) self-control stamina rather than strength, (b) studies with inactive compared to active control groups, (c) males than females, and (d) when proponents of the strength model of self-control were (co)authors of a study. Bias-correction techniques suggested the presence of small-study effects and/or publication bias and arrived at smaller effect size estimates (range: g = .13 to .24). The mechanisms underlying the effect are poorly understood. There is not enough evidence to conclude that the repeated control of dominant responses is the critical element driving training effects.

Past research found that the ingestion of glucose can enhance selfcontrol. It has been widely assumed that basic physiological processes underlie this effect. We hypothesized that the effect of glucose also depends on people's theories about willpower. Three experiments, both measuring (experiment 1) and manipulating (experiments 2 and 3) theories about willpower, showed that, following a demanding task, only people who view willpower as limited and easily depleted (a limited resource theory) exhibited improved self-control after sugar consumption. In contrast, people who view willpower as plentiful (a nonlimited resource theory) showed no benefits from glucose-they exhibited high levels of self-control performance with or without sugar boosts. Additionally, creating beliefs about glucose ingestion (experiment 3) did not have the same effect as ingesting glucose for those with a limited resource theory. We suggest that the belief that willpower is limited sensitizes people to cues about their available resources including physiological cues, making them dependent on glucose boosts for high self-control performance.self theories | implicit theories | ego depletion | cognitive performance "Ideas set free beliefs, and the beliefs set free our wills." -William James, The Energies of Man (1907, p. 14) (1) A n intriguing finding in recent years is that the short-term ingestion of glucose can improve a variety of basic cognitive and self-regulatory functions including episodic memory, information processing, attention, and self-control (2-5). For instance, studies show that the ingestion of glucose can prevent the drop in self-control performance that can otherwise follow the exertion of self-control (6-8), improving such things as persistence and the inhibition of impulses.In suggesting a close relationship between glucose and cognitive and self-regulatory outcomes, these findings raise fundamental questions about how physiological and psychological processes intersect. Popular theories suggest that glucose directly fuels brain functions, which would otherwise suffer from a lack of glucose (9-11). These theories can be taken to suggest that optimal performance on everyday cognitive and self-regulatory tasks requires frequent glucose boosts.Given the centrality of cognitive performance and self-regulation for human functioning and welfare in general, it would be striking if these functions were so fragile as to depend to a significant extent on the short-term ingestion of glucose (12, 13). Research shows that various processes in the body (such as glucose release from the liver) assure that under normal conditions the brain has ample energy supplies for neuronal functioning (14). Moreover, numerous studies show that self-control performance can be restored by various psychological manipulations (e.g., positive mood, mindfulness meditation) without glucose ingestion (15)(16)(17)(18). Taken together, these findings imply that brain functions are unlikely to depend on the short-term intake of glucose (14,19). Why then do...