The size of an object determines how much attention our brain is willing to allocate to it. However, it’s not how the perceived size of an object that counts, rather how large our brains know them to be from experience.

Image via Pixabay.

Researchers from the George Washington University (GWU) say that object size is a key factor our brain takes into account when doling out attention. The findings, they say, could pave the way for special training to enable people to better notice certain objects — such as tumors on a radiology plate or hidden items in luggage.

Size does matter

“Since a person can only pay attention to a limited amount of information at a time, our brain uses object size to determine how much attention to allocate to that object,” says Sarah Shomstein, a professor of cognitive neuroscience at the GW Columbian College of Arts and Sciences and paper co-author.

“However, the way our eyes perceive an object can be different from its actual size, such as a car appearing large when it is close and small when it is far. Our study has shown for the first time that the brain adjusts attention based on our knowledge of an object’s size, not how our eyes view it.”

For the study, Dr. Shomstein and her team showed participants images of several everyday items (of various sizes in real life). These items, however — ranging from domino blocks to whole billiards tables — were shown at the same fixed size in all photographs. The team also added ‘probe targets’ in each image. What they wanted to see was how long it took participants to find these targets within each image.

Smaller real-world objects elicited a quicker response than larger ones across the board — even though they occupied the same amount of space in the participants’ eyes. Dr. Shomstein says that this happens because the participants’ previous knowledge of object size overruled their perceived size. Because of this, their brains automatically adjusted how much attention each item received (which, in turn, made it easier or more difficult to spot the targets).

“If objects are of identical size on your eye, but you know that one of them is smaller — such as a domino nearby versus a pool table far away — you allocate more attention to the smaller item,” she explains

The team then showed participants images of everyday items and asked them to rate their size on a scale of one to six (“one” being very small and “six” being very large). The results here showed there’s a direct correlation between how participants rated the size of each object and the time it took them to respond to target stimuli within the image.

“Your own personal ratings determine how efficient you are going to be at attending to that object,” says co-author Andrew J. Collegio. “If you think the pool table is really large, then your attention is going to be less focused.”

The team hopes these findings will help us better understand how people process particular objects as they pay attention to the world around them. In the long run, they add, these findings may ever point the way to new training avenues that would improve people’s ability to pay attention to certain items in different contexts.

The paper “Attention scales according to inferred real-world object size” has been published in the journal Nature Human Behaviour.