Willpower and self-control are not subject to exhaustion like muscles, and it all comes down to the brain's special modes of operation.
You may have heard that self-control, or willpower, is similar to a muscle that tires from frequent use. This concept has deeply permeated psychology literature and everyday discussions. After a busy day full of decision-making, we feel "exhausted," as if we've depleted our internal resources.
In psychology, this phenomenon is called ego depletion. It is believed that acts of self-control drain our mental resources. For example, if you declined dessert at lunch, it will be harder to resist the temptation to watch your favorite series in the evening. This concept is intuitively appealing and offers us an excuse for self-pity in moments of fatigue. It explains how willpower feels during moments of mental strain when we resist temptations or make important decisions, and how distractions become more enticing when we are tired.
But what if this is a misconception? What if willpower is not depleted?
The ego depletion theory, which emerged in the mid-1990s, had a significant impact. Based on numerous laboratory studies, it claimed that every act of self-control, such as resisting temptations or managing emotions, uses the same limited resource (or "willpower muscle"). When this resource is depleted, we become more impulsive and less attentive.
This theory found reflection in bestsellers, corporate training, and even political life. Barack Obama, the former President of the United States, explained his choice to wear the same suits daily as a way to save his mental energy for truly significant decisions. The idea proved not only popular but also useful, allowing people to recognize mental exhaustion and develop strategies to prevent it.
However, over time, nuances emerged. In most experiments testing the ego depletion theory, participants performed one task requiring self-control and then moved on to a more challenging one. According to the theory, their performance should have declined. In everyday life, this can be compared to a situation where, after a difficult morning full of concentration at work, you find it hard to resist checking social media.
Nevertheless, meta-analyses combining results from several studies found no convincing evidence of ego depletion. Attempts to replicate the results in laboratories around the world yielded ambiguous or negative results. Even the fundamental question of "what exactly is being depleted?" remained unanswered. It was previously thought that depletion was related to blood glucose levels, but this explanation has been debunked. The more psychologists studied ego depletion, the more it eluded their definition.
Despite this, proponents of the theory continued to argue that the studies were not complex enough. Therefore, my colleagues and I decided to create a model that could provide more opportunities for ego depletion to manifest. We believed that if willpower truly resembled a muscle, then prolonged engagement in a challenging task should lead to fatigue. Their performance in subsequent self-control tasks should decline.
We conducted a 35-minute online study in which participants performed two alternating tasks. The first task was a challenging numerical version of the Stroop test, requiring participants to quickly name the number of digits while ignoring the numbers themselves, designed to test cognitive control. The second task involved observing global and local levels of information and required quick shifts in focus. This task was used to measure participants' concentration ability and effective responses over time.
Contrary to the ego depletion theory, participants adapted over time, becoming faster and more accurate, showing no systematic decline in performance even after prolonged cognitive effort.
Importantly, the difficulty of the Stroop test varied: some participants completed a "high depletion" version, while others worked with an easier version. If willpower truly worked like a muscle, the more challenging version of the test should have fatigued participants more quickly. However, the outcome was different: participants working with the "difficult version" maintained their pace, and in some cases even accelerated.
If the ego depletion model does not hold true, then a new approach is needed. One interesting alternative is the metacontrol theory proposed by cognitive psychologist Bernhard Hommel. It suggests that the brain operates on a continuum between two cognitive states: persistence and flexibility. This can be imagined as a car with two gears: persistence is a low gear for smooth climbing, while flexibility is a high gear for easy driving and navigating new routes.
When the brain operates in persistence mode, it narrows the focus of attention. You become more goal-oriented and resistant to distractions, which increases the chances of successfully tackling a difficult task. In flexibility mode, the brain is more open to new ideas and capable of integrating new information, which helps in abandoning rigid goals.
Both modes have their advantages, depending on the context. In everyday life, you may have noticed how you switch from persistence while studying to flexibility when socializing with friends. Persistence is important when completing scientific work, while flexibility helps during brainstorming or solving unexpected problems. The brain naturally switches between these states, especially when tasks drag on or rewards are uncertain.
From this perspective, what we perceive as "exhaustion" may merely be a transitional state. After prolonged mental work, the brain may shift to flexibility mode not due to a lack of resources, but as an adaptive response. Evolutionarily, this could have given our ancestors a survival advantage by allowing them to switch between modes rather than getting stuck on one task.
The metacontrol theory explains changes in performance over time and aligns with modern neurobiological data. It links changes in cognitive mode to dopaminergic activity in various brain areas, particularly in the prefrontal cortex and basal ganglia. These systems regulate the balance between persistence and flexible adaptation. The level of dopamine in certain brain areas can make us more persistent, while its movement to deeper areas helps us become more open to new ideas.
These ideas have practical implications for understanding effort, self-discipline, and failures in everyday life. The phenomenon of "breaking down" — when thoughts wander, the desire to take a break arises, or goals are re-evaluated — may reflect adaptive mode switching rather than a weakness of character or depletion of willpower.
If willpower is not a resource we lose, but a mode we exit, then moments of fatigue or distraction may be natural transitions in the cognitive system. These transitions can be shaped by context, motivation, and the environment.
Sometimes a short break is not a failure, but an opportunity to reset.
In other words, mental fatigue or feelings of weakened will are not always signs of a lack of effort. What we perceive as depletion may be the result of the system's adaptation. In such cases, it is wiser to take a pause, refresh, or change the approach. This might manifest, for example, as stepping away from your desk after a challenging task or switching from writing text to organizing your workspace. By changing the type of mental load, you give your brain a chance to reset its control mode, avoiding overexertion.
If we abandon the metaphor of "willpower as a muscle," what could be an alternative? Imagine willpower as a car with two gears that does not wear out but adapts based on the environment, goals, and internal feedback, constantly assessing the effectiveness of the current strategy based on signals such as perceived effort, progress, and expected rewards.
This does not mean abandoning discipline, but improving willpower may require less persistence and more understanding of how the brain evaluates and adapts. More precise psychological models are needed to reflect the actual workings of the brain.
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