You Have No Idea How Much Your Brain Is Ignoring

Exploring the potential of the human mind and body

The eye-opening science behind ‘inattentional blindness’

Photo: olasunkanmi ariyo/Getty Images

In an iconic study from 1999, Daniel Simons and Christopher Chabris, researchers at Harvard University, used a gorilla costume as a prop to explore visual perception.

Subjects were asked to watch a video and count the number of times players passed a basketball between a small, continually moving group of students. Partway through the video, a person dressed in a gorilla suit slowly walked into the frame, beat their chest, and walked off.

When Simons first tried the test with Harvard University students, he held his breath, but despite the gorilla being visible for nine seconds, only half of them noticed the unlikely walk-on. “Missing the gorilla is jarring. It’s natural to assume that you would see it, so it’s surprising and compelling when you realize what you’ve missed,” he says.

The study was repeated in 2010, but this time it included subjects who were aware of the original video and its findings regarding unexpected objects. Though they identified the gorilla in the new film, they failed to notice other significant changes, including the backdrop’s color (shifting from red to gold) and a player walking off the court.

So, what is failing in us? Perhaps nothing.

For excellent evolutionary reasons, people have a remarkable ability to focus on what appears, in the moment, to be essential. A person tracking an antelope or avoiding a lion needs to be fully committed — distraction is not an option. Despite the apparent survival benefits of this hyper focus, people may be unaware of significant chunks of their surroundings.

“We remember vividly all the times we have noticed something unexpected or unusual, but have no idea how many times we have missed gorillas or unicycling clowns, unless a researcher explicitly brings it to our attention.”

This phenomenon, labeled “inattentional blindness” by cognitive scientists, occurs in response to a perceptual framework evolved by humans over thousands of years.

The brain attends to “sounds and other stimuli that it deems most important,” says George Slavich, a psychologist at the University of California, Los Angeles. Without this filtering mechanism, we would be overwhelmed by stimuli, our brains unable to process the excess of information.

Research also shows that the human brain can be primed. Mentioning the word “doctor” before being shown a string of letters, and the subject is more likely to identify the word “nurse.” Priming works by stimulating an association in memory and provides further evidence of how easily attention can be influenced.

While such findings are interesting, they also raise serious concerns. A study in 2013 appearing in Psychological Science found that 83% of expert radiographers failed to notice a picture of — yes, you’ve guessed it — a gorilla in lung images. “Even expert searchers, operating in their domain of expertise, are vulnerable to inattentional blindness,” says Trafton Drew, an attention researcher at Harvard Medical School.

A study published in November 2019 asked subjects to count how many times colored shapes bounced off the edge of a computer screen. While they kept track, a cross-shaped object passed in front of their field of vision for either 1.5 or 5 seconds. Surprisingly, the display time had only a small impact on whether subjects identified the rogue shapes.

“We remember vividly all the times we have noticed something unexpected or unusual, but have no idea how many times we have missed gorillas or unicycling clowns, unless a researcher explicitly brings it to our attention,” says Vanessa Beanland, member of the Australasian College of Road Safety, and reported in New Scientist.

The unexpected may always be in plain sight, but it is often only when it becomes relevant, or potentially life-threatening, that we notice it.

This article, and others like it, originally appeared on Medium