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What do our brains learn from surprises?

Each time you have an experience that defies your expectations, your brain becomes slightly more fine-tuned.

Olgerta Asko places electrodes on a participant’s EEG cap during an experiment at the University of Oslo.
Silje Pileberg Freelance JOURNALIST
Presented by: Presented by: Presented by: University of Oslo
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How does our brain absorb information? And why do we learn from experiences?

Throughout much of the 20th century, many researchers thought the brain mainly acted as a passive receiver, taking in and processing sensory information, before sending them on to higher-level processing areas in the brain.

"These kinds of insights can also inspire better computer and AI models that have to learn from experience and deal with uncertainty, just like our brains do,” says researcher Olgerta Asko.

From the 1990s onward, growing research undermined that view.

“Today we are quite certain that our brain is a ‘prediction machine.’ It does not passively receive sensory impressions. It creates internal models with expectations about incoming external information,” says Olgerta Asko.

She is a researcher at RITMO Centre for Interdisciplinary Studies in Rhythm, Time and Motion, part of the University of Oslo.

Surprises spark brain activity

Even newborns show signs of innate expectations for sounds and visual patterns. As life progresses, our brain becomes more and more refined.

In her research, Asko measured electrical brain activity during surprises. This activity is called a ‘mismatch signal.’

Study participants heard sounds that repeated in a pattern until the pattern suddenly changed.

“If everything matches the brain's expectations, we see almost no extra response in the electrical signal. Surprises, however, produce a clear spike in activity and serve as learning signals,” she says.

Asko explains that each time the world behaves as expected, the brain's model gets stronger. Each unexpected event adjusts the model.

Explains why optical illusions fool us

This brain mechanism efficiently organises experiences, Asko explains.

“It does not need to wait for new sensory input, as it actively generates expectations about how the world works and fills in missing information,” she says.

This also explains why illusions fool us:

“The brain draws on existing knowledge, but it lacks precision and fails,” she says.

The mysterious prefrontal cortex

Thousands of studies have looked at how the brain responds to surprises. Asko focused on one area: the prefrontal cortex, located just behind the forehead.

The researcher explains that fully understanding the prefrontal cortex is one of the biggest challenges in neuroscience.

“We know it plays roles in decision-making, artistic activity, and social behavior, and it's especially large and complex in humans compared to other animals. But its exact mechanisms remain unclear,” she says.

Asko describes the prefrontal cortex as a ‘hub’ connected to many other brain regions. Does it help create the expectations that lead to surprises – and learning?

Yes, according to Asko.

Weaker signals in damaged brains

Researchers played sounds with surprise elements to participants while recording electrical brain activity. 

Some participants had damage to the prefrontal cortex, where nerve cells and their connections were destroyed in a specific area. Others did not.

The researchers then compared mismatch signals.

“Those with damage showed weaker, delayed signals, which means they have a reduced ability to prepare for potential surprises,” explains Asko.

She notes that accessing patients with this kind of brain damages is challenging, which explains why there has been little research on this topic before.

Practical benefits for patients

What does this research mean? Why does it matter which part of the brain does what?

According to Asko, this knowledge is valuable in several different ways. 

It tells us something fundamental about how the brain builds and updates expectations. It may also be important for healthcare and people with prefrontal cortex damage caused by strokes, tumors, or accidents.

“Other brain areas often compensate when one is damaged, but not for all functions, and the compensation is rarely 100 per cent,” Asko says. “Now we know that these patients may struggle to form expectations about future events and also struggle to adapt to surprises.”

She explains that this could help guide new support strategies.

“For me, the main drive is basic curiosity about how the brain works. But in the long term, these kinds of insights can also inspire better computer and AI models that have to learn from experience and deal with uncertainty, just like our brains do,” she says.

Predictions simplify life

Next time you're waiting for a bus you expected to be on time, but it's delayed, think of it as a gift.

You become slightly better prepared for next time – and more delighted when it arrives precisely on schedule.

“Or perhaps you travel to a country where buses never arrive on time? Your brain models will likely update. This helps us adapt to new environments and situations, making life much easier,” says Asko.

Reference:

Asko, O. 'Predictive processing in human prefrontal cortex: Causal contributions of orbitofrontal and lateral prefrontal subregions', Doctoral dissertation at the University of Oslo's Department of Psychology, 2026. (About the dissertation on the university's website)

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