What do you think of this fact?
Picture a short video. A few people pass basketballs to each other, and your job is simple: count the passes made by the players in white. Easy. Afterwards, the researchers ask whether you noticed the gorilla.
The gorilla nobody saw
That is the famous experiment by psychologists Daniel Simons and Christopher Chabris at Harvard University. Two teams, one in white and one in black, pass balls around. Viewers count the white team’s passes. About half a minute in, a person in a gorilla suit walks into the middle, turns to the camera, thumps its chest and walks off.
According to NPR and Smithsonian Magazine, roughly half of the viewers did not see the gorilla at all. Not a blurry glimpse, not sort of. Nothing. In one version, Chabris says, it was on screen for nine seconds.
Psychologists call this inattentional blindness. When your attention is glued to one task, anything you are not looking for can slip right past your awareness, even if it happens directly in front of your eyes.
Even the experts fall for it
Maybe you think trained professionals are immune. Trafton Drew and Jeremy Wolfe of Harvard Medical School tested that with radiologists, people whose job is to spot tiny details in medical images. They hid a gorilla the size of a matchbook in lung scans and asked the radiologists to look for cancerous nodules.
According to NPR, 83 percent of the radiologists missed the gorilla. Their eyes had passed over the spot, but because they were searching for nodules and not for gorillas, it never registered.
Bonus fact: In a 2010 sequel, viewers who already knew about the gorilla spotted it, but many missed other surprises, such as a curtain in the background changing color.
Your eyes take in far more than you ever notice. What actually lands in your head is up to your attention.