The present work suggests that self-control relies on glucose as a limited energy source. Laboratory tests of self-control (i.e., the Stroop task, thought suppression, emotion regulation, attention control) and of social behaviors (i.e., helping behavior, coping with thoughts of death, stifling prejudice during an interracial interaction) showed that (a) acts of self-control reduced blood glucose levels, (b) low levels of blood glucose after an initial self-control task predicted poor performance on a subsequent self-control task, and (c) initial acts of self-control impaired performance on subsequent self-control tasks, but consuming a glucose drink eliminated these impairments. Self-control requires a certain amount of glucose to operate unimpaired. A single act of self-control causes glucose to drop below optimal levels, thereby impairing subsequent attempts at self-control.Keywords: self-regulation, glucose, attention, emotion regulation, prejudice Self-control (or self-regulation) is the ability to control or override one's thoughts, emotions, urges, and behavior. Self-control allows for the flexibility necessary for successful goal attainment, and it greatly facilitates adherence to morals, laws, social norms, and other rules and regulations. As such, it is one of the most important and beneficial processes in the human personality structure. A burgeoning body of evidence has linked good self-control to a broad range of desirable outcomes, including healthier interpersonal relationships, greater popularity, better mental health, more effective coping skills, reduced aggression, and superior academic performance, as well as less susceptibility to drug and alcohol abuse, criminality, and eating disorders (DeWall,

Self-regulation is a highly adaptive, distinctively human trait that enables people to override and alter their responses, including changing themselves so as to live up to social and other standards. Recent evidence indicates that self-regulation often consumes a limited resource, akin to energy or strength, thereby creating a temporary state of ego depletion. This article summarizes recent evidence indicating that regular exercises in self-regulation can produce broad improvements in self-regulation (like strengthening a muscle), making people less vulnerable to ego depletion. Furthermore, it shows that ego depletion moderates the effects of many traits on behavior, particularly such that wide differences in socially disapproved motivations produce greater differences in behavior when ego depletion weakens the customary inner restraints.Self-regulation is an important personality process by which people seek to exert control over their thoughts, their feelings, their impulses and appetites, and their task performances. The human capacity for self-regulation appears to be much more extensive than what is found in other animals, which may suggest that the evolutionary pressures that guided the selection of traits that make up human nature, such as participation in cultural groups, found self-regulation to be especially adaptive and powerful (Baumeister, 2005). If so, then self-regulation may be one of the most distinctively human traits. Even if human beings are capable of more self-regulation than other animals, however, their capacity is far less than what many Correspondence concerning this article may be sent to R. Baumeister,

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Past research indicates that self-control relies on some sort of limited energy source. This review suggests that blood glucose is one important part of the energy source of self-control. Acts of self-control deplete relatively large amounts of glucose. Self-control failures are more likely when glucose is low or cannot be mobilized effectively to the brain (i.e., when insulin is low or insensitive). Restoring glucose to a sufficient level typically improves self-control. Numerous self-control behaviors fit this pattern, including controlling attention, regulating emotions, quitting smoking, coping with stress, resisting impulsivity, and refraining from criminal and aggressive behavior. Alcohol reduces glucose throughout the brain and body and likewise impairs many forms of self-control. Furthermore, self-control failure is most likely during times of the day when glucose is used least effectively. Self-control thus appears highly susceptible to glucose. Self-control benefits numerous social and interpersonal processes. Glucose might therefore be related to a broad range of social behavior.

Often people are faced with conflict between prosocial motivations for helping and selfish impulses that favor not helping. Three studies tested the hypothesis that self-regulation is useful for managing such motivational conflicts. In each study, depleted self-regulatory energy reduced willingness to help others. Participants who broke a habit, relative to participants who followed a habit, later reported reduced willingness to help in hypothetical scenarios (e.g., donating food or money; Studies 1 and 3). Controlling attention while watching a video, relative to watching it normally, reduced volunteering efforts to help a victim of a recent tragedy- but drinking a glucose drink undid this effect (Study 2). Depleted energy reduced helping toward strangers but it did not reduce helping toward family members (Study 3). Helping requires self-regulatory energy to manage conflict between selfish and prosocial motivations-a metabolically expensive process-and thus depleted energy reduces helping and increased energy (glucose) increases helping.