The Invisible Gorilla


My son came home from school one day and said he wanted to show us something that the teacher had played in class.  

He pulled up a video on his computer, which showed two teams of young people passing basketballs back and forth, one team in white shirts, one in black. He instructed us to count how many times the basketball players in the white shirts passed the ball. When the video was over, we all gave him our counts, wanting to see who’d gotten it right.  

But he wanted to know if we’d seen the gorilla.


(Spoiler Alert!) He played the video again, and sure enough, during the middle of the game, a full sized person in a gorilla suit could clearly be seen casually strolling straight through the players on the court. It even paused dead center, looked at the camera and beat his chest before strolling out of the frame.

And we hadn’t noticed it at all.

The cause: In attentional blindness, or perceptual blindness; as defined by Wikipedia, “the failure to notice a fully visible but unexpected object because attention was engaged on another task, event or object”. Intense focus on a part of reality can actually “blind” us to significant data under our very noses.  

Seeing is believing?

My local radiologist shared with me that he was given an exercise in training where he was tasked with looking for a specific abnormality on scan. When he was done, it was pointed out that he had completely missed the “Mickey Mouse” sticker that had been placed on the film.

My own “invisible gorilla”? I was recently reviewing a Quality Study for a CoC accredited program with their Quality Improvement Coordinator. I had, I thought, gone over it with a fine-toothed comb, 4.7 criteria in hand; we clearly involved the Cancer Committee in defining a problem, had found a national benchmark for comparison, had studied the problem, identified causes, instituted quality improvements, check, check, check. We reviewed again the next day and asked ourselves, “where is our before and after data?”. The data was obviously available, but we needed to include it in our presentation. We felt bad for almost missing a key piece of our study and then I remembered the invisible gorilla.

(To share with friends, search for “The Monkey Business Illusion” by Daniel Simons, on YouTube).