Seeing fast, acting slow: how the brain processes what you see

23 Mar 2018



Identifying an object in an unexpected location is quick, but responding to it is slowed down.

Identifying an object in an unexpected location is quick, but responding to it is slower, according to new QBI research. It comes down to our prior knowledge of an experience and what parts of our brain processes this information first.

The visual world is complex, but much of what we encounter every day is predictable. For example, at a café, we know the coffee order will be placed on top of the counter, not under a table, and the small paper packets beside it are more likely to contain sugar than salt.

This prior knowledge helps us to identify objects in predictable circumstances more quickly than things we see in an unfamiliar or inconsistent context.

Prior knowledge is acquired without effort or intent through our daily interactions with the world. However, how and when the brain uses this knowledge as it processes visual information is not well understood - until now.

Familiar experiences help the brain predict 

QBI's Professor Jason Mattingley and colleagues Associate Professor Paul Dux and Dr Michelle Hall from the School of Psychology, recorded brain activity in a group of people while they viewed mandala-like assortments of shapes on a computer screen.

The shapes were more likely to appear in certain locations. For example, a purple mandala almost always appeared at the top right of the screen, but occasionally a different mandala would appear there instead.

Over time, participants developed an expectation of where each mandala would appear, but they were never explicitly told the precise pattern. Each mandala was mapped to a key on the keyboard, and participants were asked to indicate which shape was on the screen at each point in time by pressing the relevant key as quickly as possible.

Participants were slower to respond – and had different brain activity – when the mandala appeared in an infrequent location on the screen.

Unlike previous studies, which suggested that prior knowledge is integrated with sensory input at the earliest stage of visual processing, the researchers found that this difference in brain activity arose at the middle stages of visual processing.

This means you can quickly identify the shape of an object without prior knowledge, but identifying its corerct location is affected by how it matches your previous knowledge and experience.

The researchers continue to investigate how the brain uses prior knowledge when processing visual information. They are using brain imaging techniques to record patterns of brain activity while participants view surprising and unsurprising shapes.


This article was originally published on The Brain Dialogue. Read the original article.