Ego depletion

American social psychologist Roy Baumeister and his colleagues proposed a model that described self-control like a muscle, which can become both strengthened and fatigued. The researchers proposed that initial use of the "muscle" of self-control could cause a decrease in strength, or ego depletion, for subsequent tasks. Later experimental findings showed support for this muscle model of self-control and ego depletion.

An experiment by Baumeister, Ellen Bratslavsky, Mark Muraven, and Dianne Tice in 1998, demonstrated some of the first evidence that ego depletion had effects in diverse contexts or situations. They showed that people who initially resisted the temptation of chocolates were subsequently less able to persist on a difficult and frustrating puzzle task. They attributed this effect to ego depletion, which resulted from the prior resisting of a tempting treat. Additionally, it was demonstrated that when people voluntarily gave a speech that included beliefs contrary to their own, they were also less able to persist on the difficult puzzle, indicating a state of ego depletion. This effect was not nearly as strong when individuals were not given a choice and were "forced" to write a counter-attitudinal speech. Thus, they proposed that both the act of choice and counter-attitudinal behaviors draw upon the same pool of limited resources. While giving a counter-attitudinal speech is expected to produce ego depletion, introducing the element of choice further increases the level of experienced depletion. These findings demonstrated the effects of ego depletion in differential situations and emphasized that ego depletion may not be context-specific. The experiment drew together earlier proposals of a strength model of willpower into a single experimental paradigm. With this study, Baumeister and his colleagues therefore provided the first direct experimental evidence of ego depletion, and initiated research interest on the subject.

The role of glucose as a specific form of energy needed for self-control has been explored by researchers. Glucose, a sugar found in many foods, is the primary fuel for the body and the brain. Multiple experiments have connected self-control depletion to reduced blood glucose, and suggested that self-control performance could be replenished by consuming glucose. Some of the findings were later questioned. However, several experiments have found that resource depletion effects can be reversed by simply tasting (but not swallowing or consuming) sweet beverages, which can have rewarding properties. Others have suggested that the taste of sugar (but not artificial sweetener) has psycho-physiological signaling effects.

A 2007 experiment by Segertrom and Nes found HRV (heart rate variability) to be a marker for ego depletion as well as an index for self-control power before the task.

Neural activity associated with self-control failure has been examined using neurophysiological techniques. According to cognitive and neuroscientific models of mental control, a "conflict-monitoring/error-detection system" identifies discrepancies between intended goals and actual behaviors. Error-related negativity (ERN) signals are a waveform of event-related potentials, which appear to be generated in the anterior cingulate cortex when individuals commit errors in various psychological tasks. Using electroencephalography (EEG) recordings, Inzlicht and Gutsell found that individuals who had undergone an emotion-suppression task displayed weaker ERN signals compared to individuals who had not undergone emotion-suppression tasks. Inzlicht and Gutsell interpreted this pattern as evidence that self-control exertion can weaken neural mechanisms linked to conflict monitoring.

The majority of ego depletion studies have been carried out on university students, which raises concerns about how generalizable the results really are. Dahm and colleagues (2011) reported that adults over 40 did not show depletion effects in a standard manipulation, while younger university students did, and suggested that ongoing maturation of self-control brain regions could contribute to this difference.

Ego depletion has also been implicated in guilt and prosocial behavior. The feeling of guilt, while unpleasant, is necessary to facilitate adaptive human interactions. The experience of guilt is dependent on one's ability to reflect on past actions and behaviors. Ego depletion has been shown to hinder the ability to engage in such reflection, thereby making it difficult to experience guilt. Since guilt typically leads to prosocial behavior, ego depletion will therefore reduce the good deeds that often result from a guilty conscience. In the study by Xu and colleagues, some participants were required to suppress their emotions while watching a movie about butchering animals, which resulted in a depleted state. Participants were then induced to feel guilty by playing a game in which an opponent player was blasted with loud, unpleasant noises when they made errors. At the end of the experiment, participants were given a chance to leave money for a subsequent participant and were also given the choice of making a charitable donation. These were the measures of pro-social behavior. The results of this study indicated that people who experienced ego depletion felt less guilty and donated less money than non-depleted people. This demonstrates that ego depletion has an indirect effect on prosocial behavior by decreasing one's ability to experience guilt.

An individual's perceived level of fatigue has been shown to influence their subsequent performance on a task requiring self-regulation, independent of their actual state of depletion. Clarkson and colleagues (2010) termed this effect "illusory fatigue." This was shown in an experiment in which participants engaged in a task that was either depleting or non-depleting, which determined each individual's true state of depletion. Ultimately, when participants were led to believe their level of depletion was lower than their true state of depletion, they performed much worse on a difficult working memory task. This indicates that an increased perceived level of fatigue can hinder self-regulatory performance independent of the actual state of depletion.

Studies have associated ego depletion with short-term impairments in self-regulation. These effects can, however, be temporarily buffered by external motivations and beliefs in unlimited willpower. …

An experiment performed by Kathleen Vohs and Todd Heatherton demonstrated how ego depletion is particularly relevant when considering chronic dieters compared to non-dieters. Chronic dieters constantly work at resisting their cravings and limiting their food intake. Vohs and Heatherton showed that the task of regulating food intake could be undermined in the face of tempting snacks, especially when the individual was experiencing a state of ego depletion. Both dieters and non-dieters attempted to suppress their emotional responses while watching a movie. Afterwards, participants were required to consume ice cream in order to engage in a taste test. The major finding was that dieters who suppressed their emotional responses to the movie experienced more ego depletion than those who were not required to suppress their emotions. Additionally, those individuals subsequently ate much more ice cream in the taste-testing task. Non-dieters did not show the same self-regulatory failures as dieters in these tasks. Therefore, it seems that the act of dieting itself is a form of resource expenditure.

Research has found that competitive athletes' mental determination can be hindered after completing a difficult cognitive task more than after completing an easy cognitive task. This indicates that the hindering effects of ego depletion can be applied not only to subsequent performance on cognitive tasks, but on physical tasks, as well.

In the world of consumerism, individuals are faced with decisions and choices that require the use of valuable energy resources in order to make informed purchases while resisting the temptation of impulsive or unnecessary purchases. Consumers are constantly bombarded with a broad range of options. In order to make the best choice, one must compare the many different aspects of various products. The complexity of consumer decisions in itself can result in ego depletion. This, in turn, could impact any subsequent decisions consumers must make. When consumers are depleted, they are more likely to become passive and make impulsive decisions that may not align with their true values.

Consumers are faced with choices of different price ranges and product qualities in the market. Having many options can make consumers feel overwhelmed, causing ego depletion. …

A 2007 experiment reported that inducing a positive mood can buffer the impairing effects of ego depletion on subsequent performance. Positive mood was induced by getting individuals to watch comedy videos or by giving them a surprise gift. Positive mood seemed to allow people to recover faster from ego depletion and, furthermore, improved their ability to self-regulate. There is no claim that positive mood can provide a general benefit to people who had not previously engaged in self-regulatory tasks; rather, positive mood can restore depleted individuals' capacity to self-regulate. Furthermore, this experimental work does not consider in depth the mechanisms by which performance is restored. It is not known whether positive mood counteracts ego depletion or whether positive mood merely motivates an individual to persist in a task, despite one's depleted state.

The ego-depletion effect itself (without mood intervention) has, however, been shown to be unrelated to mood changes, as shown in multiple ego-depletion experiments that either controlled for mood or saw no mood changes.