We’ve all felt it: that sluggish, foggy feeling that sets in during a long exam or intense work session. You may have started strong, but by the end, you’re dragging — even if you still want to do well. This isn’t burnout; it’s mental fatigue. And it turns out, it has a real, measurable impact on performance.
A recent study titled “Mental Fatigue and Exam Performance: The Importance of Measuring Effort” explored how students experience cognitive fatigue during testing, and why understanding mental effort is just as critical as measuring outcomes like test scores.
What the Study Looked At
The researchers wanted to know: Does increasing mental effort during an exam relate to worse performance?
To answer this, they tracked how students’ subjective mental effort changed over time as they completed a long exam. Instead of just recording the final answers, participants were asked to rate how much mental effort they were putting in after different sections of the test. This allowed the researchers to see how cognitive fatigue accumulated in real time.
Interestingly, they found that students didn’t all experience fatigue in the same way. Some reported feeling relatively consistent throughout, while others showed steep increases in fatigue — especially as the test progressed.
Fatigue Affects Performance — Especially Later On
The results were clear: students who experienced sharper increases in mental fatigue tended to perform worse on the second half of the exam. In other words, it wasn’t just how hard the questions were — it was how mentally drained the students became.
This has big implications. Exams are typically seen as fixed, one-size-fits-all tools to measure ability. But what if some students are underperforming simply because they’re cognitively exhausted by the time they reach the second half? If mental fatigue can affect scores, then what we’re measuring may be skewed by how depleted someone is, not just what they know.
Why Measuring Mental Effort Matters
Here’s where it gets exciting — especially for those of us building tools that rely on real-time cognitive data. This research reinforces the idea that mental effort is trackable, variable, and meaningful.
By measuring effort — whether through self-report, behavior, or biometric data — we can:
- Detect fatigue early and adapt tasks accordingly
- Understand individual differences in how people handle mental load
- Design better assessments and interfaces that are cognitively sustainable
- Support performance, not just observe it
This goes beyond education. For any cognitively demanding activity — from professional certification exams to air traffic control, from remote work to online learning — understanding mental fatigue is crucial.
A Smarter Approach to Performance
Think about this: if we knew someone’s cognitive fatigue level in real time, we could adjust workflows, insert micro-breaks, or even delay critical decisions until they’re mentally ready. That’s not just personalization — that’s optimizing performance through empathy and data.
What this study shows is that mental fatigue isn’t invisible. It’s not just “feeling tired” — it’s a dynamic signal that can be measured, tracked, and responded to. And when we do that, we open the door to smarter systems and more humane expectations.
Final Thought
Mental effort is the hidden engine behind so much of what we do. Yet most systems ignore it. This research gives us a clear reminder: If we care about outcomes, we need to start caring about mental fatigue too.
At CuesHub, we’re exploring how real-time signals — from focus to fatigue — can be used to improve human performance. Because when we measure what matters, we can design systems that don’t just work, but work with us.
Reference
Szpunar, K. K., & Osman, M. (2022). Mental fatigue and exam performance: The importance of measuring effort. In M. S. Khader (Ed.), Advances in Applied Cognitive Psychology (Vol. 3, pp. 27–35). Society for Applied Research in Memory and Cognition.