Why your mind goes blank during exams?

You’ve studied. You’ve practiced. Yet, the moment the math exam begins, your mind turns into a foggy void. You stare at the question: 38 + 63 =, but it might as well be hieroglyphs. What just happened?

Psychologist WEI Wei, an associate professor at Zhejiang University Department of Psychology and Behavioral Sciences , has been studying this all-too-familiar phenomenon. Her latest research, published in Contemporary Educational Psychology, sheds light on the way anxiety, especially math anxiety, interferes with our ability to think clearly. And the key player? Something called short-term memory.

WEI Wei recently conducted a study involving 178 third- and fourth-grade students in Zhejiang Province. The children were given dozens of two-digit addition and subtraction problems. The findings confirmed what many have long suspected: the higher a child’s math anxiety, the more mistakes they made.

But it’s not just about nerves. WEI Wei argues that the root problem lies deeper in how anxiety compresses our short-term memory, making it harder to hold and manipulate information when we need it most.

Short-term memory, often compared to a mental notepad, temporarily stores and processes the data needed to solve problems. When we’re anxious, WEI wei says, this mental notepad shrinks. “It’s not that students don’t understand the material,” she explains. “It’s that anxiety hijacks the cognitive resources they need to perform.”

The idea isn’t new. For decades, psychologists have described how anxiety drains our working memory, which includes both short-term storage and what’s called executive control—our ability to focus and manipulate information.

But WEI Wei’s study digs even deeper. She wanted to know which part of working memory takes the bigger hit when anxiety strikes: the “storage” or the “execution”?

To find out the story behind it, her team designed an experiment mimicking real-world math tasks. When students saw a problem like “38 + 63” on a computer screen, their brains first had to mentally sketch out the vertical alignment of the numbers, a task handled by short-term memory. Then, they had to perform the calculations, relying on executive control. The final answer, 101, had to be assembled step-by-step, with carried numbers temporarily stored along the way.

By cleverly separating these mental stages, WEI Wei discovered something new: anxiety primarily disrupts the storage part of working memory rather than the execution. In other words, it’s like trying to cook a meal without ingredients, rather than forgetting how to cook.

“The metaphor I use is cooking,” WEI Wei says. “No matter how good a chef you are, you can’t make dinner if you don’t have the ingredients. Anxiety robs you of those ingredients.”

This isn’t just a local issue. The OECD’s triennial global education survey, known as PISA, has been tracking student anxiety since 2012. In 2022, the data showed a consistent pattern: students with higher math anxiety score significantly lower on math assessments, regardless of nationality. Alarmingly, the proportion of students reporting math-related stress has nearly doubled over the past decade from 30% in 2012 to 59% in 2015.

According to the PISA 2022 report, each 1% increase in math anxiety corresponds to an 18-point drop in math scores, a steep price for nervousness.

The short-term memory component of working memory—rather than executive function—mediates the relationship between math anxiety and performance on calculation tasks.

So, what can we do?

WEI Wei offers a surprisingly simple and feasible solution: use paper.

“When students are allowed to use scrap paper and write out problems, it eases the load on short-term memory,” she explains. “Mental math puts more pressure on that limited space, increasing the risk of performance collapse under stress.”

Her study confirms this. In tasks that required precise calculation, where short-term memory demands were higher, anxiety had a significantly stronger negative effect than in simpler approximation tasks. The implication? When anxiety levels are high, precision suffers, but only when memory space is overloaded.

Telling students “don’t be anxious” is rarely helpful. WEI Wei argues that a more constructive approach is to build classroom strategies around memory scaffolding.

This could mean encouraging written step-by-step problem-solving instead of expecting answers to be computed silently. It also means recognizing individual differences: “Two students might get the same problem wrong, but the reasons could be totally different,” WEI Wei says.

She urges educators to focus not just on results but on the thinking process behind those results. Veteran teachers, she notes, often require students to write out full solutions—not just for grading, but to better understand how each child thinks and where support is needed.

So the next time your mind goes blank in an exam or you see your child freeze mid-problem, consider this: it may not be a lack of ability, but a lack of cognitive space.

Grab a piece of paper. Write things down. Give your short-term memory some breathing room. And perhaps, with a little more room to think, the answers will start to appear.

Adapted and translated from the article by DAN Hanyu, WANG Yun, and ZHA Meng  
Translator: FANG Fumin
Photo: The research team 
Editor: TIAN Minjie