Fatigue and Slower Thinking Predict When We Override Exhaustion

Everyone knows the feeling: the workday is over, exhaustion has settled in, and yet something — a deadline, a workout, a social commitment — pulls us into one more effortful task. Psychologists call this act of pushing through despite tiredness a fatigue override, and it has long been treated as an idiosyncratic quirk of willpower. A new coordinated analysis, drawing on data from six separate experience sampling studies, suggests it is anything but random. The research, published in Communications Psychology, shows that two everyday signals — how fatigued a person feels and how quickly their mind is processing information at a given moment — reliably predict whether that person will go on to override their fatigue in the hours that follow. The finding reframes fatigue override not as a mysterious act of grit, but as a predictable outcome of measurable momentary states that fluctuate across ordinary daily life.

The study belongs to a growing class of research that relies on ecological momentary assessment, or EMA, a method in which participants are prompted repeatedly on their smartphones or other devices to report on their current state as they move through real environments. Rather than asking people in a laboratory to recall how tired they were last week, EMA captures fatigue, cognitive performance and behavior in near real time, dozens of times per participant across several days. This matters because fatigue is notoriously unstable: it rises and falls with sleep, workload, time of day and countless small events. By sampling these fluctuations intensively, researchers can model how a person’s state at one moment relates to their choices at the next, a question that one-shot questionnaires simply cannot answer.

Coordinated analysis adds a further layer of rigor. Instead of pooling raw data from different studies into a single giant dataset — an approach that can be confounded by differences in measures, sampling schedules and populations — the researchers analyzed each of the six studies separately using an identical analytic plan, then combined the results. If an effect appears consistently across independently collected datasets with different participants, designs and instruments, the odds that it is a statistical fluke of any one study shrink dramatically. In an era when psychology has been forced to confront replication failures, this strategy has become one of the field’s most trusted tools for separating robust phenomena from artifacts.

The central result concerns the temporal ordering of states and behavior. At each prompting occasion, participants rated their current fatigue and completed brief tasks or self-reports indexing their processing speed — essentially, how rapidly they could take in and respond to information. The analysis then examined whether these momentary measurements predicted fatigue override at a subsequent occasion: instances in which participants engaged in demanding activity despite reporting being tired. Across the six studies, higher momentary fatigue and slower processing speed each forecast a greater likelihood of subsequent override. In other words, the very signals that would seem to argue for rest — feeling drained and thinking sluggishly — were the states that most often preceded a decision to push on anyway.

That counterintuitive pattern is precisely what makes the finding scientifically interesting. A simple homeostatic account of fatigue would predict the opposite: the more exhausted people feel, the more they should disengage and recover. Instead, the data suggest that fatigue often functions as a signal to be weighed rather than an automatic command to stop. When tiredness is high, the question of whether to continue becomes salient, and many people resolve it in favor of continued effort. The authors’ coordinated design showed that this relationship was not an artifact of any single study’s sample, measure or analytic choice, lending the pattern the kind of cross-contextual consistency that single studies rarely achieve.

The role of processing speed adds a cognitive dimension to the story. Processing speed is one of the most basic markers of cognitive efficiency, and it is known to degrade under sleep deprivation, illness and sustained mental effort. The finding that slower processing at one moment predicts later fatigue override hints at a possible internal logic: people may notice their thinking has become labored and interpret that slowing as evidence that they need to compensate — working harder, pushing longer, or forcing themselves through tasks they would normally finish easily. Alternatively, slowing may simply co-occur with the kinds of demanding days, heavy workloads and poor nights of sleep that also generate obligations that cannot be dropped. The coordinated analysis cannot fully adjudicate between these interpretations, but by demonstrating that the association holds across six datasets, it establishes that the link is real enough to deserve that closer scrutiny.

Methodologically, the study illustrates why momentary designs are transforming the science of self-regulation. Traditional between-person studies compare tired people with rested people and conclude that fatigue changes behavior. But such comparisons confound stable traits — some people are chronically more tired, more conscientious or more burdened — with the within-person dynamics that actually drive decisions in the moment. EMA designs flip the question: within the same person, when fatigue rises above their own typical level, what happens next? The answer from this coordinated analysis is that both the subjective feeling of tiredness and the objective-ish marker of slowed cognition carry predictive information about the person’s own subsequent behavior, above and beyond their average tendencies. This within-person framing is crucial for anyone hoping to intervene: you cannot change someone’s average fatigue easily, but you can detect and respond to momentary spikes.

The practical implications reach into occupational health, medicine and everyday self-management. Fatigue override is a double-edged phenomenon. On one side, it underwrites resilience — the parent who still cooks dinner after a brutal shift, the clinician who finishes rounds despite exhaustion, the student who keeps studying when every instinct says stop. On the other, chronic overriding of fatigue is implicated in burnout, sleep debt accumulation, medical errors and the stubborn persistence of overwork cultures. If momentary fatigue and processing speed reliably flag when override is likely, they could be built into early-warning tools: wearable or smartphone-based systems that notice when a user’s tiredness and cognitive slowing are peaking and prompt a deliberate decision about whether continuing is truly necessary. Such tools would not forbid effort; they would simply make the trade-off visible at the moment it is being made.

The findings also speak to theoretical debates about the function of fatigue itself. One influential view treats fatigue as a motivational signal — an internal computation about the costs and benefits of continued effort — rather than as a simple depletion of a finite resource. The new results fit that framework: fatigue does not mechanically shut behavior down; instead, it changes the landscape of decisions people face, and both the intensity of the feeling and the accompanying cognitive slowing inform how people respond. That fatigue and processing speed each contributed predictive power suggests the brain may be integrating multiple channels of information — how drained the body feels and how well the mind is running — when calibrating whether to persist. Future work, the authors and observers note, will need to test which downstream consequences follow from override in these moments: does pushing through restore a sense of control, or does it deepen the fatigue that prompted it?

For now, the study’s quiet contribution is to make an everyday drama measurable. Six datasets, each capturing the texture of ordinary days, converge on the same conclusion: the moments before we override our fatigue are not silent. They are marked by feelings we can report and cognitive changes we can measure, and together those signals foreshadow the choice to keep going. As experience sampling methods spread through psychology, medicine and workplace research, the boundary between feeling exhausted and acting exhausted is becoming an object of precise science — one that may eventually help people decide, more deliberately, when pushing through is worth it and when rest is the smarter move.

Subject of Research: Predicting subsequent fatigue override from momentary fatigue and processing speed using coordinated analysis of six ecological momentary assessment studies

Article Title: Fatigue and processing speed predict subsequent fatigue override, evidence from a coordinated analysis of six EMA studies

Article References: Hernandez, R., Schneider, S., Hoogendoorn, C. J., Kratz, A. L., Yang, C.-H., Ehde, D. M., Stone, A. A., Jin, H., Fanning, J., Hakun, J. G., Fritz, N. E., Gonzalez, J. S., & Moore, R. C. (2026). Fatigue and processing speed predict subsequent fatigue override, evidence from a coordinated analysis of six EMA studies. Communications Psychology. https://doi.org/10.1038/s44271-026-00537-1

Image Credits: AI Generated

DOI: 10.1038/s44271-026-00537-1

Keywords: fatigue, fatigue override, processing speed, ecological momentary assessment, coordinated analysis, self-regulation, effort, cognitive performance, burnout, experience sampling, Communications Psychology, replication