Why do some people see things faster than others?

Kasandra Brabaw | Aug 05, 2021

How quickly do you spot a car slamming on its brakes, a coffee cup tipping over, or a friend waving hello?

The widely held view that humans immediately notice what’s in front of them is undoubtedly wrong, according to Chicago Booth’s Alexander Todorov and a team of researchers, who find that recognizing visual stimuli is neither instantaneous nor universal. “The brain prioritizes information for consciousness,” the researchers write, but every brain prioritizes differently, which leads some of us to process visual stimuli more quickly than others. Citing the results of a series of 10 experiments they conducted involving dozens of Hebrew University students, they report that there are meaningful differences in how quickly people see something. 

The “something” in the experiments involved words and other stimuli such as numbers, human faces, and emotional expressions. The team conducted the tests to determine nonconscious visual prioritization speed, or NVPS. Participants looked through 3D glasses at flashing stimuli and were asked to press a button to indicate whether the stimulus image was to the left or the right. 

But the researchers also used masks, generally colorful or busy images, to obscure the stimuli. In some experiments, the masks were shown constantly in one eye while the stimuli slowly showed up in the other. In other experiments, the masks were flashed at both eyes between stimuli images. For example, in one test, some participants saw a colorful square in the right eye while a human face slowly showed up in the left eye. The participants indicated where and when the face appeared. 

The researchers find no correlation between the speed at which people notice an object and similar cognitive traits such as conscious cognitive speed, perceptual threshold (the point at which some stimulus breaks through consciousness), visual short-term memory, and attentiveness. They do, however, find a moderate correlation between self-reported sensitivity and NVPS, via a shortened version of the highly sensitive person test (a checklist test posing statements that include “I am deeply moved by the arts or music” and “I notice and enjoy delicate or fine scents, tastes, sounds, and works of art”). The researchers theorize that how quickly people process visual stimuli may affect how they experience the world. 

Other implications could be that those who quickly notice visual stimuli may be more aware of their surroundings—and be better able to quickly reach out and keep that cup of coffee from tipping over. Those who take longer to process visual stimuli might crash into the braking car in front of them or only respond to a wave after the friend has turned away. However, those who react more quickly might also take less time to think and thus may make less deliberate decisions, the researchers suggest.