A study says faster reactions can come with fuzzier memories: What happens when your brain knows what to expect

Picture a game of catch after school. Your friend keeps throwing the ball towards the same side. After a few throws, you begin getting into position early. You have spotted a pattern. Now imagine being asked to draw the exact path of the last ball. Getting ready for a catch does not automatically give you a detailed record of what happened.

A University of Sydney study found a similar trade-off in a laboratory. People reacted faster to expected events, but remembered their exact locations less precisely.

What the University of Sydney study discovered

The 2026 research was published in the Journal of Neuroscience. Ziyue Hu was the first author. The study was done by Dominic M. D. Tran and the senior author was Reuben Rideaux.


Forty people observed visual flashes around a circle. They recorded their brain activity with EEG. They also measured pupil responses. The team changed the patterns so some flashes were more predictable than others.


Participants reacted faster and more accurately to expected flashes. Yet they were less precise when asked to reproduce where those flashes had appeared. Unexpected flashes left a more precise record. The catch game illustrates the finding. The researchers tested flashes, rather than balls.

How the brain gets ready before something happens

The study points to two separate stages. Before an event appears, preparation helps support a fast response. After it appears, the brain represents predictable information with less precision.

Researchers call preparation for an action motor preparation. Think of getting your hands ready to catch. The movement has a head start, even though the event has not finished unfolding.

The study linked the early advantage to attention. Its later reduction in sensory precision was independent of attention. In other words, being more ready to respond did not remove the loss of fine detail.

Why a fast response is different from a detailed memory

The result can sound confusing. How could someone perform better while remembering less accurately? The tasks asked different questions. One measured how quickly and accurately participants responded. Another measured how precisely they could reproduce a location.

Knowing enough to choose the right response is different from keeping an exact record.

Imagine answering “left” when asked which side a ball passed. You might get that answer right. Marking its precise position on a diagram demands more detail.

The distinction matters when describing the research. Expected events did not make participants worse at everything. Their responses improved while their location precision declined.

Predictive coding explains the brain’s educated guesses

Neuroscientist Karl Friston’s work describes a framework called predictive coding. The brain uses internal models to anticipate incoming information. Differences between its prediction and the evidence can help it update those models.

An internal model is like a working explanation of what usually happens. In the catch game, repeated throws provide a pattern. You have a reason to expect another throw towards the same side.


The framework treats perception as more than collecting information. Existing expectations help shape how incoming information is interpreted.

A prediction error is a mismatch between the expectation and what happens. The word “error” describes the mismatch. It does not mean someone has behaved badly.

Attention helps you choose where to get ready

Psychologist Michael I. Posner’s research offers useful background. His work with colleagues found that people detected visual signals faster when a cue indicated where the signal would appear.

Imagine knowing which window a friend will wave from. You can direct attention there before the wave.

Selective attention means giving some information priority over other information. Preparing for a likely location can help with a response.

Expecting something and paying attention to it are related ideas, but they are different. The Sydney researchers separated them experimentally. The approach let them examine which effects depended on attention.

Why an unexpected event can stand out

Return to the game. Your friend suddenly throws towards the other side. The familiar pattern no longer fits. Within predictive coding, unexpected evidence provides a reason to revise an internal model.

The Sydney study found more precise brain representations of unexpected flashes. Differences appeared within roughly 100 to 200 milliseconds after a flash. Such timing concerns rapid processing, rather than a deliberate decision to remember less.

The findings concern controlled visual tasks. They do not prove that familiar routines make everyone generally unobservant.

FAQs

Can the brain see the future?

No. It can prepare for likely events using patterns.

Does familiarity always weaken memory?

It doesn't seem so. The study tested specific visual information, rather than every kind of memory.