Ego depletion

Ego depletion is the idea that self-control or willpower draws upon conscious mental resources that can be taxed to exhaustion when in constant use with no reprieve (with the word "ego" used in the psychoanalytic sense rather than the colloquial sense).^[1] When the energy for mental activity is low, self-control is typically impaired, which would be considered a state of ego depletion. In particular, experiencing a state of ego depletion impairs the ability to control oneself later on. A depleting task requiring self-control can have a hindering effect on a subsequent self-control task, even if the tasks are seemingly unrelated. Self-control plays a valuable role in the functioning of the self on both individualistic and interpersonal levels. Ego depletion is therefore a critical topic in experimental psychology, specifically social psychology, because it is a mechanism that contributes to the understanding of the processes of human self-control. There have both been studies to support^[2] and to question^[3] the validity of ego-depletion as a theory.^[4]

Some meta-analyses and studies have questioned the size and existence of the ego depletion effect.^[3] The ultimate validity and conclusions of those later studies are not universally agreed upon.^[5] Martin Hagger and Nikos Chatzisrantis, whose 2010 meta-analysis seemed to support the existence of the ego depletion effect,^[5] subsequently performed a pre-registered 23-lab replication study that did not find an ego-depletion effect.^[6]

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 researches 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.^[2]

A key 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.^[1] 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. This experiment was critical in that the researchers synthesized ideas proposed by prior studies that had suggested evidence for a strength model of willpower. 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.^[7] Some of the findings were later questioned.^[8] However, several recent experiments have found that resource depletion effects can be reversed by simply tasting (but not swallowing or consuming) sweet beverages,^[9][10][11] which can have rewarding properties. Others have suggested that the taste of sugar (but not artificial sweetener) has psycho-physiological signaling effects.^[12]

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.^[13]

Neural activity associated with self-control failure has recently 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.^[14] 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.^[15] 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.^[14] These findings demonstrate preliminary evidence that depletion experienced after exerting self-control can weaken neural mechanisms responsible for 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. The effects of age are unknown, but maybe younger people are more susceptible to the effects of ego depletion, given that the areas of the brain involved in self-control continue to develop until the mid 20s. For example, a recent study found that people over the age of 40 did not become ego depleted following a typical depletion manipulation, whereas younger university students did.^[16]

In a state of ego depletion, an individual's impaired ability to self-regulate can be implicated in a wide range of undesirable and maladaptive behaviors, such as acts of aggression. Knowledge and strategies to counteract ego depletion would therefore be highly beneficial in various real-life situations. ^{[citation needed]}

A recent experiment showed that inducing a positive mood can buffer the impairing effects of ego depletion on subsequent performance.^[28] 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. Thus, positive affect is just a way to counteract ego depletion after a person is depleted.

Although up until the mid-2010s there was widespread confidence in the robustness of the ego depletion effect, a substantial body of research has since cast doubt on the replicability of the effect.

A 2010 meta analysis of 198 independent tests found the effect significant with a moderate effect size (d = .6). Even after accounting for possible unpublished failed studies, the analysis concluded that it is extremely unlikely that the effect doesn't exist.^[36] In 2015, a meta analysis of over 100 studies by Carter and McCullough argued that the 2010 meta-analysis failed to take publication bias into account. They showed statistical evidence for publication bias. When they statistically controlled for publication bias, the effect size estimate was small (d = .2) and not significantly different from zero.^[37][38] Michael Inzlicht and colleagues praised Carter's meta analysis, but argued that bias-correction techniques are not precise enough to give a precise control size estimate.^[5][39] In response, Cunningham and Baumeister argued that Carter and McCullough analysis contained errors in its data collection and in the various analyses used.^[5]

Ulrich Schimmack (2016) conducted a meta-analysis of published studies and found that most studies could produce significant results only with the help of random sampling error. Based on the low power of studies, one would expect a large number of non-significant results, but these results are missing from published articles. This finding supports Carter and McCullough's meta-analysis that showed publication bias with a different statistical method. Schimmack's replicability report also identified a small set of studies with adequate power that provided evidence for ego-depletion. These studies are the most promising studies for a replication project to examine whether ego-depletion effects can be replicated consistently across several independent laboratories.^[40]

In 2016, a major multi-lab replication study (2141 participants) carried out at two dozen labs across the world using a single protocol failed to find any evidence for ego depletion.^[3][41] In response, Baumeister and Vohs argued that Baumeister's original protocol was rejected by the project coordinators, and after discussion was stalled, he only reluctantly agreed to a task that differed to some degree from the original 1998 studies.^[42] However, a subsequent, separate multi-lab replication project, led by Kathleen Vohs and involving 36 labs testing 3531 participants,^[43] also failed to find an ego-depletion effect (d = 0.06; an order of magnitude smaller than the effect size estimate in the original Hagger meta-analysis). Replication difficulties have also emerged for 5 additional protocols (operationalizations) of the basic ego depletion effect.^[44]