Self-control relies on glucose as a limited energy source: willpower is more than a metaphor

Cognitive task performance causes impaired maximum force production in human hand flexor muscles

The purpose of this study was to investigate effects of demanding cognitive task performance on intermittent maximum voluntary muscle contraction (MVC) force production. Participants performed either a modified Stroop or control task for 22 min. After the first min and at 3-min intervals thereafter, participants rated fatigue, perceived mental exertion and performed a 4-s MVC handgrip squeeze. A mixed ANOVA showed a significant interaction, F(7, 259)=2.43, p=.02, with a significant linear reduction in MVC force production over time in the cognitively depleting condition (p=.01) and no change for controls. Ratings of perceived mental exertion, F(7, 252)=2.39, p<.05, mirrored the force production results with a greater linear increase over time in the cognitive depletion condition (p<.001) compared to controls. Findings support current views that performance of cognitively demanding tasks diminishes central nervous system resources that govern self-regulation of physical tasks requiring maximal voluntary effort.

Drifting from slow to "D'oh!": working memory capacity and mind wandering predict extreme reaction times and executive control errors

A combined experimental, individual-differences, and thought-sampling study tested the predictions of executive attention (e.g., Engle & Kane, 2004) and coordinative binding (e.g., Oberauer, Süβ, Wilhelm, & Sander, 2007) theories of working memory capacity (WMC). We assessed 288 subjects' WMC and their performance and mind-wandering rates during a sustained-attention task; subjects completed either a go/no-go version requiring executive control over habit or a vigilance version that did not. We further combined the data with those from McVay and Kane (2009) to (1) gauge the contributions of WMC and attentional lapses to the worst performance rule and the tail, or τ parameter, of reaction time (RT) distributions; (2) assess which parameters from a quantitative evidence-accumulation RT model were predicted by WMC and mind-wandering reports; and (3) consider intrasubject RT patterns--particularly, speeding--as potential objective markers of mind wandering. We found that WMC predicted action and thought control in only some conditions, that attentional lapses (indicated by task-unrelated-thought reports and drift-rate variability in evidence accumulation) contributed to τ, performance accuracy, and WMC's association with them and that mind-wandering experiences were not predicted by trial-to-trial RT changes, and so they cannot always be inferred from objective performance measures.

The role of glucose in self-control: another look at the evidence and an alternative conceptualization

The strength model suggests that self-control relies on a limited resource. One candidate for this resource is glucose. Counter to the proposals of the glucose hypothesis, this study argues that the resource issue is one of allocation, not of limited supply. It addresses the argument from three perspectives: the evolution of mental processes at the species level, the adaptation of these same processes at the individual level, and the physiology of glucose transport. It is argued here that the brain has both sufficient resources and resource delivery mechanisms with which to support self-control but that these resources are allocated in accordance with personal priorities. As an alternative to the limited resource model, the current study proposes a resource-allocation model of self-control and presents several testable hypotheses.

Temporal Patterns of Subjective Experiences and Self-Regulation during Ramadan Fasting among Elite Archers: A Qualitative Analysis

Purpose

Some major competitions (e.g. London Olympics, 2012) are scheduled during the Ramadan fasting month. Little attention has been given to explore the archers’ performance related subjective experiences with a qualitative method. Therefore, this study addressed individual archers’ subjective experiences within the framework of self-regulation during Ramadan.

Methods

Eleven elite Malaysian Muslim fasting archers volunteered to participate in the study. Grounded theory was the qualitative approach used to examine the subjective experiences of athletes during Ramadan. Interviews were conducted and inductive content analysis was adopted to identify the temporal patterns of self-regulation of subjective experiences across the fasting period.

Results

Inductive content analysis identified (a) physical, (b) mental,(c) emotional, (d) behavioral, and (e) spiritual experiences. Overall patterns revealed that experiences associated with physical, emotional, behavioral, and spiritual dimensions dominated in the first phase of fasting, while the mental dimension surfaced increasingly in the latter phase of fasting.

Conclusions

The trend showed changes in the patterns of experiences among the major domains across the temporal dimension. Athletes reported increased subjective experiences in mental factors toward the latter half of the fasting period. Practitioners should emphasize on mental aspects of training, as these appear to be salient in archery performance.

Cognitive task demands, self-control demands and the mental well-being of office workers

The cognitive task demands of office workers and the self-control demands of their work roles were measured in a sample of 196 employees in two different office layouts using a self-report questionnaire, which was circulated electronically. Multiple linear regression analysis revealed that both factors were associated with mental well-being, but not with physical well-being, while controlling for exposure to psychosocial stressors. The interaction between cognitive task demands and self-control demands had the strongest association with mental well-being, suggesting that the deleterious effect of one was greater when the other was present. An exploratory analysis revealed that the association was stronger for employees working in a large open-plan office than for those working in smaller offices with more privacy. Frustration of work goals was the cognitive task demand having the strongest negative impact on mental well-being. Methodological limitations and scale psychometrics (particularly the use of the NASA Task Load Index) are discussed. STATEMENT OF RELEVANCE: Modern office work has high mental demands and low physical demands and there is a need to design offices to prevent adverse psychological reactions. It is shown that cognitive task demands interact with self-control demands to degrade mental well-being. The association was stronger in an open-plan office.

Restorative biological processes and health

Research on psychological influences on physiology primarily focuses on biological responses during stressful challenges, and how those responses can become dysregulated with prolonged or repeated exposure to stressful circumstances. At the same time, humans spend considerable time recovering from those challenges, and a host of biological processes involved in restoration and repair take place during normal, non-stressed activities. We review restorative biological processes and evidence for links between psychosocial factors and several restorative processes including sleep, wound healing, antioxidant production, DNA repair, and telomerase function. Across these biological processes, a growing body of evidence suggests that experiencing negative emotional states, including acute and chronic stress, depressive symptoms, and individual differences in negative affectivity and hostility, can influence these restorative processes. This review calls attention to restorative processes as fruitful mechanisms and outcomes for future biobehavioral research.

Self-Regulatory Strength Depletion and Muscle-Endurance Performance: A Test of the Limited-Strength Model in Older Adults

Self-regulation consumes a form of strength or energy. The authors investigated aftereffects of self-regulation depletion on muscle-endurance performance in older adults. Participants (N= 61, mean age = 71) were randomized to a self-regulation-depletion or control group and completed 2 muscle-endurance performance tasks involving isometric handgrip squeezing that were separated by a cognitive-depletion task. The depletion group showed greater deterioration of muscle-endurance performance than controls,F(1, 59) = 7.31,p= .009. Results are comparable to those of younger adults in a similar study and support Baumeister et al.’s limited-strength model. Self-regulation may contribute to central-nervous-system fatigue; however, biological processes may allow aging muscle to offset depletion of self-regulatory resources affecting muscle-endurance performance.

Cumulative psychological strain and future strain in Naval personnel: is executive function the elephant in the room?

Psychological strain was measured in 592 Naval personnel at four phases using the General Health Questionnaire (GHQ-12). The GHQ-12 Likert score was summed to generate a measure of cumulative strain, which was best predicted by the Cognitive Failures Questionnaire (CFQ) score, effort-reward imbalance and a measure of organisational commitment. Point strain at phase IV was best predicted by CFQ score, whereas need for recovery was best predicted by over-commitment to work role. Susceptibility to strain, both cumulatively over 2 years and 12 months in the future appears to depend on a cognitive factor measured by the CFQ. This factor was more strongly associated with strain than with fatigue. Psychosocial stress exposure at work played a lesser role in predicting cumulative and future strain, possibly because these stressors were of an acute nature. The findings are discussed with reference to recent research on attention and anxiety and some of the practical implications are considered. STATEMENT OF RELEVANCE: There is renewed interest in intrinsic variables that predict adverse reactions to occupational stress. The paper presents evidence that self-reported cognitive failure is a vulnerability factor for future episodes of psychological strain. The paper strengthens the conclusions of a previous article and adds empirical support to recent research on the links between anxiety and attention.

Understanding impulsive aggression: Angry rumination and reduced self-control capacity are mechanisms underlying the provocation-aggression relationship

Interpersonal provocation is a common and robust antecedent to aggression. Four studies identified angry rumination and reduced self-control as mechanisms underlying the provocation-aggression relationship. Following provocation, participants demonstrated decreased self-control on an unpleasant task relative to a control condition (Study 1). When provoked, rumination reduced self-control and increased aggression. This effect was mediated by reduced self-control capacity (Study 2). State rumination following provocation, but not anger per se, mediated the effect of trait rumination on aggression (Study 3). Bolstering self-regulatory resources by consuming a glucose beverage improved performance on a measure of inhibitory control following rumination (Study 4). These findings suggest that rumination following an anger-inducing provocation reduces self-control and increases aggression. Bolstering self-regulatory resources may reduce this adverse effect.

Cognitive neuroscience of self-regulation failure

Self-regulatory failure is a core feature of many social and mental health problems. Self-regulation can be undermined by failures to transcend overwhelming temptations, negative moods and resource depletion, and when minor lapses in self-control snowball into self-regulatory collapse. Cognitive neuroscience research suggests that successful self-regulation is dependent on top-down control from the prefrontal cortex over subcortical regions involved in reward and emotion. We highlight recent neuroimaging research on self-regulatory failure, the findings of which support a balance model of self-regulation whereby self-regulatory failure occurs whenever the balance is tipped in favor of subcortical areas, either due to particularly strong impulses or when prefrontal function itself is impaired. Such a model is consistent with recent findings in the cognitive neuroscience of addictive behavior, emotion regulation and decision-making.

Resource depletion promotes automatic processing: implications for distribution of practice

Recent models of cognition include two processing systems: an automatic system that relies on associative learning, intuition, and heuristics, and a controlled system that relies on deliberate consideration. Automatic processing requires fewer resources and is more likely when resources are depleted. This study showed that prolonged practice on a resource-depleting mental arithmetic task promoted automatic processing on a subsequent problem-solving task, as evidenced by faster responding and more errors. Distribution of practice effects (0, 60, 120, or 180 sec. between problems) on rigidity also disappeared when groups had equal time on resource-depleting tasks. These results suggest that distribution of practice effects is reducible to resource availability. The discussion includes implications for interpreting discrepancies in the traditional distribution of practice effect.

Practicing self-control lowers the risk of smoking lapse

Recent research has suggested that practicing small acts of self-control can lead to an improvement in self-control performance. Because smoking cessation requires self-control, it was hypothesized that a treatment that builds self-control should help in quitting smoking. A total of 122 smokers either practiced small acts of self-control for 2 weeks before quitting smoking or practiced a task that increased their awareness of self-control or feelings of confidence, without exercising self-control. Their smoking status was assessed using daily telephone calls and biochemically verified. Individuals who practiced self-control remained abstinent longer than those who practiced tasks that did not require self-control. Supplemental analyses suggested that the increased survival times were a product of building self-control strength and were not produced by changes in feelings that practicing should help in cessation, effort exerted on the practice task, or thinking more about self-control while practicing.

Sweetened blood cools hot tempers: physiological self-control and aggression

Aggressive and violent behaviors are restrained by self-control. Self-control consumes a lot of glucose in the brain, suggesting that low glucose and poor glucose metabolism are linked to aggression and violence. Four studies tested this hypothesis. Study 1 found that participants who consumed a glucose beverage behaved less aggressively than did participants who consumed a placebo beverage. Study 2 found an indirect relationship between diabetes (a disorder marked by low glucose levels and poor glucose metabolism) and aggressiveness through low self-control. Study 3 found that states with high diabetes rates also had high violent crime rates. Study 4 found that countries with high rates of glucose-6-phosphate dehydrogenase deficiency (a metabolic disorder related to low glucose levels) also had higher killings rates, both war related and non-war related. All four studies suggest that a spoonful of sugar helps aggressive and violent behaviors go down.

An effect of mood on the perception of geographical slant

Previous research has shown that hills appear steeper to those who are fatigued, encumbered, of low physical fitness, elderly, or in declining health (Bhalla & Proffitt, 1999; Proffitt, Bhalla, Gossweiler, & Midgett, 1995). The prevailing interpretation of this research is that observers' perceptions of the environment are influenced by their capacity to navigate that environment. The current studies extend this programme by investigating more subtle embodied effects on perception of slant; namely those of mood. In two studies, with two different mood manipulations, and two estimates of slant in each, observers in a sad mood reported hills to be steeper. These results support the role of mood and motivational factors in influencing spatial perception, adding to the previous work showing that energetic potential can influence perception.

FIT – Do Something Different

Two 3-month longitudinal studies examined weight loss following a 1-month behavioral intervention (FIT-DSD) focusing on increasing participants’ behavioral flexibility and breaking daily habits. The goal was to break the distal habits hypothesized as playing a role in unhealthy dietary and activity behaviors. The FIT-DSD intervention required participants to do something different each day and to engage in novel weekly activities to expand their behavioral repertoire. These activities were not food- or exercise-related. In Study 1, the FIT-DSD program was compared with a control condition where participants engaged in daily tasks not expected to influence behavioral flexibility. Study 2 used an active or quasicontrol group in which half the participants were also on food diets. Measures in both studies were taken pre-, post-, and post-postintervention. In Study 1, FIT-DSD participants showed greater weight loss that continued post-postintervention. In Study 2, all participants on the FIT-DSD program lost weight, weight loss continued post-postintervention, and participants who were also dieting lost no additional weight. A dose relationship was observed between increases in behavioral flexibility scores and weight loss, and this relationship was mediated by calorie intake. Corresponding reductions in BMI were also present. Increasing behavioral flexibility may be an effective approach for tackling obesity and also provides affective and potential life-skill benefits.

Resisting Weakness of the Will

I develop an account of weakness of the will that is driven by experimental evidence from cognitive and social psychology. I will argue that this account demonstrates that there is no such thing as weakness of the will: no psychological kind corresponds to it. Instead, weakness of the will ought to be understood as depletion of System II resources. Neither the explanatory purposes of psychology nor our practical purposes as agents are well-served by retaining the concept. I therefore suggest that we ought to jettison it, in favour of the vocabulary and concepts of cognitive psychology.

Implicit Delegation of Responsibility

In everyday life, people often exert self-control not only for their own sake but also for the sake of close others. Here, the authors examine the specific case of joint self-control—when multiple people must simultaneously exert self-control for mutual success—in the context of close relationships. The authors test the hypothesis that people use situational cues to determine if one member of the relationship bears more responsibility for exerting self-control than the other. In this article, the authors test the specific cue of past behavior and find in two studies that participants who exert self-control on behalf of the relationship on a preliminary task continue to exert self-control on behalf of the relationship on a secondary task compared to those who exerted less self-control on the preliminary task. The authors explain these results by focusing on the role that expectations about behaviors play in contributing effort to a difficult or unpleasant task.

The type B behavior pattern as a moderating variable of the relationship between stressor chronicity and health behavior

To test the hypotheses that Type B individuals would engage in more preventive and less risk-related behaviors under high stress than Type As, 155 students were administered questionnaires pertaining to the TABP, daily hassles, and health behavior. As predicted, in six out of seven regression analyses, Type Bs engaged in more preventive, and fewer risk-related behaviors under high stress, than those who self-reported as Type A. Self-regulation mechanisms are proposed to help account for these effects.

Ego Depletion Is Not Just Fatigue

Is the self-regulation failure that comes from prior exertions of self-regulation—the ego-depletion effect—the result of fatigue? A reading of the literature suggests that self-regulatory resource depletion and fatigue might be overlapping constructs, but direct empirical evidence is lacking. The authors put this question to the test by subjecting half of their participants to total sleep deprivation for 24 hours whereas others were rested; they crossed this factor with a self-regulation manipulation in which participants did or did not suppress their emotional reactions to a film. The authors' measure of self-regulation was aggressive responses in a game involving blasting noise at an opponent. Contrary to expectations, there was no effect of sleep deprivation on aggression. In confirmation of the limited-resource model, the authors found that depleted participants were more aggressive than nondepleted participants (irrespective of fatigue condition). Lax self-regulation seems to be from a lack of self-regulatory capacity, not fatigue.

Glucose promotes controlled processing: Matching, maximizing, and root beer

Participants drank either regular root beer or sugar-free diet root beer before working on a probability-learning task in which they tried to predict which of two events would occur on each of 200 trials. One event (E1) randomly occurred on 140 trials, the other (E2) on 60. In each of the last two blocks of 50 trials, the regular group matched prediction and event frequencies. In contrast, the diet group predicted E1 more often in each of these blocks. After the task, participants were asked to write down rules they used for responding. Blind ratings of rule complexity were inversely related to E1 predictions in the final 50 trials. Participants also took longer to advance after incorrect predictions and before predicting E2, reflecting time for revising and consulting rules. These results support the hypothesis that an effortful controlled process of normative rule-generation produces matching in probability-learning experiments, and that this process is a function of glucose availability.

Ego Depletion—Is It All in Your Head?

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.

Stereotype Threat Affects Financial Decision Making

The research presented in this article provides the first evidence that one’s decision making can be influenced by concerns about stereotypes and the devaluation of one’s identity. Many studies document gender differences in decision making, and often attribute these differences to innate and stable factors, such as biological and hormonal differences. In three studies, we found that stereotype threat affected decision making and led to gender differences in loss-aversion and risk-aversion behaviors. In Study 1, women subjected to stereotype threat in academic and business settings were more loss averse than both men and women who were not facing the threat of being viewed in light of negative stereotypes. We found no gender differences in loss-aversion behavior in the absence of stereotype threat. In Studies 2a and 2b, we found the same pattern of effects for risk-aversion behavior that we had observed for loss-aversion behavior. In addition, in Study 2b, ego depletion mediated the effects of stereotype threat on women’s decision making. These results suggest that individuals’ decision making can be influenced by stereotype concerns.

Implicit attitudes and explicit motivation prospectively predict physical activity

BACKGROUND

Contemporary approaches to physical activity motivation and promotion focus on explicit motivational processes which regulate intentional physical activity. Less is known about the role of implicit processes, which may be instrumental in regulating habitual aspects of unintentional (i.e., incidental) physical activity (PA).

PURPOSE

To test the proposition that the routine nature of unintentional PA makes it amenable to control by implicit processes.

METHODS

Participants (N = 201) completed measures of explicit motivation (i.e., efficacy beliefs, outcome expectations, behavioral intentions, perceived behavioral control) and implicit attitudes toward physical activity, and then wore a pedometer for 1 week.

RESULTS

Implicit attitudes positively predicted PA after controlling for well-established predictors of intentional physical activity.

CONCLUSIONS

PA motivation involves both explicit and implicit processes, and PA promotion efforts may be enhanced by attending to relevant implicit motivation processes.

Work demands and need for recovery from work in ageing seafarers

This study was conducted on a population of seafarers serving in the Royal Fleet Auxiliary (RFA), the organisation providing support at sea to the Royal Navy. An investigation into work-related fatigue in RFA personnel onboard ships was carried out following changes to the regulations concerning maximum retirement age, to determine whether age was associated with recovery from work demands. A total of 322 personnel aged from 19 to 61 years were interviewed onboard seven RFA ships. The Need for Recovery scale was used to measure fatigue and work demands exposure was measured using the Baecke questionnaire and the NASA Task Load Index. It was found that older personnel did not have higher work-related fatigue than younger personnel. A measure of frustration at work was found to be most strongly related to work-related fatigue, even in seafarers who carried out physically demanding jobs. Work-related fatigue was found to accumulate over time in personnel who continued to be exposed to work demands onboard a ship. Finally, a relatively high level of work-related fatigue was found in the RFA sample as a whole, which may hold implications for management interventions. It was concluded that older personnel in the RFA can cope with the day-to-day demands of working life as well as younger personnel, possibly due to a 'survivor effect', whereby those personnel who do not cope as well with work demands leave and find a different job, leaving only those who successfully deal with the demands of working life at sea. STATEMENT OF RELEVANCE: In order to manage work demands in seafarers, it is important to identify the most fatiguing demands. Age is of interest because of the demographic ageing of the workforce. Age was not associated with a higher need for recovery. Psychological work demands had a greater effect on need for recovery than physical work demands.

Selbstkontrollanforderungen bei der Arbeit

Zusammenfassung. Gegenstand der vorliegenden Studie ist die Überprüfung der psychometrischen Eigenschaften von drei Skalen zur Erfassung verschiedener Formen von Selbstkontrollanforderungen bei der Arbeit (wie Impulskontrolle, Überwinden innerer Widerstände, Ablenkungen widerstehen). Neuere Theorievorstellungen und Befunde aus der Grundlagenforschung legen die Annahme nahe, dass das Bewältigen dieser Selbstkontrollanforderungen eine bedeutsame Belastungsquelle bei der Arbeit darstellt. Die in zwei beruflichen Tätigkeitsfeldern erhobenen Daten belegen, dass die Skalen drei distinkte, moderat korrelierte Anforderungsformen abbilden. Die Skalen verfügen zudem über zufriedenstellende interne Konsistenzen und Test-Retest-Reliabilitäten. Darüber hinaus konnten sowohl im Querschnitt als auch im Längsschnitt signifikante positive Zusammenhänge mit Indikatoren der Arbeitsbeanspruchung als Validitätskriterien nachgewiesen werden (wie z.B. Burnout und Fehlzeitenmaße).

Self-regulatory deficits in fibromyalgia and temporomandibular disorders

Chronic pain conditions such as fibromyalgia (FM) and temporomandibular disorders (TMDs) are accompanied by complex interactions of cognitive, emotional, and physiological disturbances. Such conditions are complicated and draining to live with, and successful adaptation may depend on ability to self-regulate. Self-regulation involves capacity to exercise control and guide or alter reactions and behavior, abilities essential for human adjustment. Research indicates that self-regulatory strength is a limited source that can be depleted or fatigued, however, and the current study aimed to show that patients with FM and TMD are vulnerable to self-regulatory fatigue as a consequence of their condition. Patients (N=50) and pain-free matched controls (N=50) were exposed to an experimental self-regulation task followed by a persistence task. Patients displayed significantly less capacity to persist on the subsequent task compared with controls. In fact, patients exposed to low self-regulatory effort displayed similar low persistence to patients and controls exposed to high self-regulatory effort, indicating that patients with chronic pain conditions may be suffering from chronic self-regulatory fatigue. Baseline heart rate variability, blood glucose, and cortisol predicted persistence, more so for controls than for patients, and more so in the low vs. high self-regulation condition. Impact of chronic pain conditions on self-regulatory effort was mediated by pain, but not by any other factors. The current study suggests that patients with chronic pain conditions likely suffer from chronic self-regulatory fatigue, and underlines the importance of taking self-regulatory capacity into account when aiming to understand and treat these complex conditions.

Does the brain consume additional glucose during self-control tasks?

A currently popular model of self-control posits that the exertion of self-control relies on a resource, which is expended by acts of self-control, resulting in less of this resource being available for subsequent acts of self-control. Recently, glucose has been proposed as the resource in question. For this model to be correct, it must be the case that A) performing a self-control task reduces glucose levels relative to a control task and B) performing a self-control task reduces glucose relative to pre-task levels. Evidence from neurophysiology suggests that (A) is unlikely to be true, and the evidence surrounding (B) is mixed, and is unlikely to be true for subjects who have not recently fasted. From the standpoint of evolved function, glucose might better be thought of as an input to decision making systems rather than as a constraint on performance.

Self-Control Depletion Leads to Increased Risk Taking

Previous research has found that individuals low in trait self-control are more likely to take excessive risks than individuals high in trait self-control. The authors expand on this by examining the causal effects of state fluctuations in self-control on subsequent risk taking. Using the self-control strength model, the authors predicted that depleted individuals would take more risks than individuals who did not exert self-control initially. This was tested in two experiments, using both self-reports and performance on the Balloon Analogue Risk Task. In both experiments, greater risk taking by depleted participants was related only to the amount of self-control previously exerted. This suggests that situational decrements in self-control strength lead to greater risk taking. Additional data suggest that the effects of depletion on taking chances are above and beyond the effects of trait self-control. This may help to explain situational effects, such as why conscientious people sometimes take unnecessary risks.

Self-control without a "self"?: common self-control processes in humans and dogs

Self-control constitutes a fundamental aspect of human nature. Yet there is reason to believe that human and nonhuman self-control processes rely on the same biological mechanism--the availability of glucose in the bloodstream. Two experiments tested this hypothesis by examining the effect of available blood glucose on the ability of dogs to exert self-control. Experiment 1 showed that dogs that were required to exert self-control on an initial task persisted for a shorter time on a subsequent unsolvable task than did dogs that were not previously required to exert self-control. Experiment 2 demonstrated that providing dogs with a boost of glucose eliminated the negative effects of prior exertion of self-control on persistence; this finding parallels a similar effect in humans. These findings provide the first evidence that self-control relies on the same limited energy resource among humans and nonhumans. Our results have broad implications for the study of self-control processes in human and nonhuman species.

Building Self-Control Strength: Practicing Self-Control Leads to Improved Self-Control Performance

Self-control performance may be improved by the regular practice of small acts of self-control. Ninety-two adults' self-control capacity was assessed using the stop signal paradigm before they started practicing self-control and again at the end of two weeks. Participants who practiced self-control by cutting back on sweets or squeezing a handgrip exhibited significant improvement in stop signal performance relative to those who practiced tasks that did not require self-control. Participants who did not practice self-control believed that the tasks should improved self-control, engaged in tasks that were effortful and made self-control salient, but did not actually require self-control. Supplemental analyses suggested that only practicing self-control built self-control capacity; the improved outcomes cannot be explained by self-fulfilling prophecies, increased self-efficacy or awareness of self-control. The results may have implications for understanding the development of self-control in both children and adults, as well as clinical implications for treating disorders that involve low self-control.