Beliefs about willpower determine the impact of glucose on self-control

Abstract

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...

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