Why Students Sometimes Perform Worse in Exams Than Expected

Person Centre
Dec 3
4 min read

Understanding “Blank Mind”, Avoidable Mistakes, Hidden Stress & Preparation Issues

Many students, including high-achieving secondary and university students, notice that their exam performance is lower than expected, even when they fully understand the content during study or revision. Parents often report similar concerns about their children. Common experiences include:

“My mind went blank during the exam.”
“I made mistakes I never make at home.”
“I don’t feel anxious, but something felt off.”
“I rechecked my answers but still missed tiny details.”

Psychology and cognitive science research explain why this happens. Below are five evidence-supported reasons, followed by insights on how a psychology-informed approach can help.

1. Working Memory Overload (Cognitive Load from the Task Itself)

What is working memory?

Working memory is like the brain’s temporary “mental workspace” where information is held and manipulated while solving problems. For example, remembering a formula while calculating or keeping multiple steps in mind simultaneously.

Why does overload occur?

Exams require juggling multiple tasks: reading questions, deciding on methods, performing calculations, keeping track of steps, and self-monitoring. When too many demands compete for the same workspace, mistakes occur even if the student knows the material. As a result, errors may result from structural cognitive limits rather than lack of knowledge or effort.

2. Hidden Anxiety

While working memory overload comes from task demands, hidden anxiety affects attention, the brain’s ability to focus on what matters now. Anxiety can subtly hijack attention, pulling resources away from the task, reducing working memory efficiency, and making small mistakes more likely.

Attentional Control Theory shows that even mild anxiety disrupts the goal-directed attentional system, leading to impaired reading, calculation, and reasoning, even when students feel calm.

Students may overthink, second-guess, or internally monitor too much, draining cognitive resources.This explains “blank mind” or “missed details” even when knowledge is sufficient.

3. Overthinking & Perfectionism

Students often think excessively about:

“What exactly is this question asking?”
“Which question should I do first?”
“What if I get this wrong?”

Over-monitoring steals attention and working memory capacity. Overthinking can impair performance under pressure through distraction or excessive conscious control.

Overthinking is often a product of hidden anxiety combined with perfectionism, and it can impede our ability to pay attention.

This explains why students sometimes miss obvious errors, even when double-checking. Test strategies and structured self-monitoring can mitigate these risks.

4. Language Processing Under Time Pressure (Especially Relevant for Hong Kong / Taiwan Students)

Reading in a second language (such as English) under tight time limits increases working memory demand, especially for non-native speakers. Misreading, skipping key words, or misinterpreting instructions are common. Reading in a second language under cognitive load consumes more mental resources, increasing errors.

5. Preparation Issues: Procrastination, Deadline-Fighting & Sleep

Students who cram the night before an exam may fail to consolidate knowledge from short-term to long-term memory. Lack of sleep further reduces memory retrieval and cognitive function during the exam. Procrastination increases stress, leaving less time for effective study and review.

Individual Differences Matter

Individual factors, such as prior knowledge, familiarity with content, long-term memory schemas, processing speed, motivation, and stress resilience, greatly influence how much “load” causes overload. Anxiety and time pressure affect students differently. In practice, what overwhelms one student may be manageable for another. This highlights the importance of a flexible, personalised approach to supporting exam performance.

So How Psychology, CBT & Positive Psychology Help

Awareness of internal processes: Understanding how working memory, attention, fatigue, language, and preparation affect performance helps students become observers rather than victims of mistakes.
Reducing hidden anxiety: Improving attentional control and cognitive efficiency by managing subtle worry improves performance without adding pressure.
Building confidence and resilience: Focusing on strengths, mastery, self-efficacy, and a growth mindset supports calm, resourceful exam performance.
Better preparation: Helping students plan, distribute study time, and implement retrieval practice strategies strengthens memory and reduces last-minute cramming.

At Person Centre, we offer a holistic approach for secondary school students, university students, and parents seeking study skills and psychological support, particularly around exam performance and test anxiety. If you or your child would benefit from personalised study skills or psychological support, please feel free to contact us for an initial consultation. We are here to listen, understand your needs, and support you every step of the way, with options available at an affordable price that fits your budget.

Some suggested readings on these topics:

Almarzouki, A. F., Mandili, R. L., Salloom, J., Kamal, L. K., Alharthi, O., Alharthi, S., Khayyat, N., & Baglagel, A. M. (2022). The Impact of Sleep and Mental Health on Working Memory and Academic Performance: A Longitudinal Study. Brain Sciences, 12(11), 1525. https://doi.org/10.3390/brainsci12111525

Baddeley, A. (2012). Working Memory: Theories, Models, and Controversies. Annual Review of Psychology, 63(1), 1–29. https://doi.org/10.1146/annurev-psych-120710-100422

Beilock, S. L., & Carr, T. H. (2005). When High-Powered People Fail: Working Memory and “Choking Under Pressure” in Math. Psychological Science, 16(2), 101–105. https://doi.org/10.1111/j.0956-7976.2005.00789.x

Conte, F., Malloggi, S., Rosa, O. D., Ficca, G., & Giganti, F. (2025). Sleep Benefits Prose Memory Consolidation in University Students. Brain Sciences, 15(3). https://doi.org/10.3390/brainsci15030265

Eysenck, M. W., Derakshan, N., Santos, R., & Calvo, M. G. (2007). Anxiety and cognitive performance: Attentional control theory. Emotion, 7(2), 336–353.

Gimmig, D., Huguet, P., Caverni, J.-P., & Cury, F. (2006). Choking under pressure and working memory capacity: When performance pressure reduces fluid intelligence. Psychonomic Bulletin & Review, 13(6), 1005–1010. https://doi.org/10.3758/bf03213916

Landsman, M., Escamilla, G., & Matyas, J. (2023). Test Anxiety and Perfectionism. Journal of Student Research, 12(3). https://doi.org/10.47611/jsrhs.v12i3.4839

Leong, R. L. F., & Chee, M. W. L. (2023). Understanding the Need for Sleep to Improve Cognition. Annual Review of Psychology, 74(1), 27–57. https://doi.org/10.1146/annurev-psych-032620-034127

Shin, J., Lee, H. J., Park, H., Hong, Y., Song, Y. K., Yoon, D. U., & Oh, S. (2023). Perfectionism, test anxiety, and neuroticism determines high academic performance: a cross-sectional study. BMC Psychology, 11(1), 410. https://doi.org/10.1186/s40359-023-01369-y

von der Embse, N., Jester, D., Roy, D., & Post, J. (2018). Test anxiety effects, predictors, and correlates: A 30-year meta-analytic review. Journal of Affective Disorders, 227(1), 483–493. https://doi.org/10.1016/j.jad.2017.11.048

Wang, H., Zhang, X., Jin, Y., & Ding, X. (2024). Examining the relationships between cognitive load, anxiety, and story continuation writing performance: a structural equation modeling approach. Humanities and Social Sciences Communications, 11(1). https://doi.org/10.1057/s41599-024-03840-6