Lots and lots of invisible gorillas

Would you notice a gorilla entering the room you’re in right now? Are you sure about that?

I share a famous study in Simply Put by psychologists Daniel Simons and Christopher Chabris, which shows that many of us might not notice that strange occurrence. Especially when we’re busy, we’re subject to a phenomenon known as “inattentional blindness,” the ability to miss something right in front of our faces. Here’s my summary from that chapter:

“In an aggressively beige, nondescript hallway, six students move about in a circular pattern. Half of them are dressed in white shirts, and the others wear black shirts. Each color-coordinated team passes a basketball back and forth among themselves, smiling as they perform the demonstration in front of a closed bank of elevator doors.

A few seconds after they begin, an actor in a gorilla suit walks through the group, stares at the camera and pounds its chest, then heads off in the other direction. The students keep passing the ball.

Weird, right? That must have caught your attention.

Not necessarily. When the researchers who designed this test showed the scene to participants, tasking them before it played to count how many passes the team in white makes, only 42 percent of viewers noticed the gorilla. Incredibly, most viewers counted the fifteen passes the team made and saw nothing out of the ordinary.”

That result is already surprising, but maybe we can chalk up the results to the participants being amateurs. What if we had professionals doing the observation?

That’s exactly what researchers Trafton Drew, Melissa L. H. Vo, and Jeremy M. Wolfe asked when they revisited the mystery of the “invisible” gorilla several years later.

In their experiment, they tasked a group of radiologists with a routine lung nodule detection test, something they’ve done countless times. Only this time, the researchers inserted a picture of a gorilla on the CT scans.

By the way, we’re not talking about a few pixels here. This is what the image looked like, the gorilla being 48 times larger than the average lung nodule that they were supposed to be looking for:

Pretty obvious, right? Again, not so fast. Here are the results:

“83% of radiologists did not see the gorilla. Eye-tracking revealed that the majority of those who missed the gorilla looked directly at the location of the gorilla. Even expert searchers, operating in their domain of expertise, are vulnerable to inattentional blindness.”

The researchers go on to say that this is not an indictment of radiologists in particular. But it illustrates again that even when we think we know our stuff, we often don’t.