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Mon February 11, 2013

Why Even Radiologists Can Miss A Gorilla Hiding In Plain Sight

Originally published on Thu February 14, 2013 8:37 am

This story begins with a group of people who are expert at looking: the professional searchers known as radiologists.

"If you watch radiologists do what they do, [you're] absolutely convinced that they are like superhuman," says Trafton Drew, an attention researcher at Harvard Medical School.

About three years ago, Drew started visiting the dark, cavelike "reading rooms" where radiologists do their work. For hours he would stand watching them, in awe that they could so easily see in the images before them things that to Drew were simply invisible.

"These tiny little nodules that I can't even see when people point to them — they're just in a different world when it comes to finding this very, very hard-to-find thing," Drew says.

But radiologists still sometimes fail to see important things, and Drew wanted to understand more. Because of his line of work, he was naturally familiar with one of the most famous studies in the field of attention research, the Invisible Gorilla study.

In that groundbreaking study, research subjects are shown a video of two teams of kids — one team wears white; the other wears black — passing two basketballs back and forth between players as they dodge and weave around each other. Before it begins, viewers are told their responsibility is to do one thing and one thing only: count how many times the players wearing white pass the ball to each other.

This task isn't easy. Because the players are constantly moving around, viewers really have to concentrate to count the throws.

Then, about a half-minute into the video, a large man in a gorilla suit walks on screen, directly to the middle of the circle of kids. He stops momentarily in the center of the circle, looks straight ahead, beats his chest, and then casually strolls off the screen.

The kids keep playing, and then the video ends and a series of questions appear, including: "Did you see the gorilla?"

"Sounds ridiculous, right?" says Drew. "There's a gorilla on the screen — of course you're going to see it! But 50 percent of people miss the gorilla."

This is because when you ask someone to perform a challenging task, without realizing it, their attention narrows and blocks out other things. So, often, they literally can't see even a huge, hairy gorilla that appears directly in front of them.

That effect is called "inattentional blindness" — which brings us back to the expert lookers, the radiologists.

Drew wondered if somehow being so well-trained in searching would make them immune to missing large, hairy gorillas. "You might expect that because they're experts, they would notice if something unusual was there," he says.

He took a picture of a man in a gorilla suit shaking his fist, and he superimposed that image on a series of slides that radiologists typically look at when they're searching for cancer. He then asked a bunch of radiologists to review the slides of lungs for cancerous nodules. He wanted to see if they would notice a gorilla the size of a matchbook glaring angrily at them from inside the slide.

But they didn't: 83 percent of the radiologists missed it, Drew says.

This wasn't because the eyes of the radiologists didn't happen to fall on the large, angry gorilla. Instead, the problem was in the way their brains had framed what they were doing. They were looking for cancer nodules, not gorillas. "They look right at it, but because they're not looking for a gorilla, they don't see that it's a gorilla," Drew says.

In other words, what we're thinking about — what we're focused on — filters the world around us so aggressively that it literally shapes what we see. So, Drew says, we need to think carefully about the instructions we give to professional searchers like radiologists or people looking for terrorist activity, because what we tell them to look for will in part determine what they see and don't see.

Drew and his co-author Jeremy Wolfe are doing more studies, looking at how to help radiologists see both visually and cognitively the things that hide, sometimes in plain sight.

Copyright 2013 NPR. To see more, visit http://www.npr.org/.

Transcript

RENEE MONTAGNE, HOST:

This is MORNING EDITION, from NPR News. I'm Renee Montagne.

STEVE INSKEEP, HOST:

And I'm Steve Inskeep. Throughout this morning, we're hearing more about Pope Benedict's resignation. Vatican Radio has released tape of the Pope discussing his decision in Latin.

(SOUNDBITE OF VATICAN RADIO BROADCAST)

POPE BENEDICT XVI: (Latin spoken)

INSKEEP: Now, a translation of the Pope's written statement quotes him saying that "in today's world, his job requires strength of body and mind - strength, which in the last few months, has deteriorated in me." The phrase in today's world is noteworthy. For centuries, before this day, many pontiffs grew old and infirm, but none resigned, for more than 600 years.

Now today In Your Health, we have a story that teaches us more about how we see the world. Here's NPR's Alix Spiegel.

ALIX SPIEGEL, BYLINE: This story about how you see the world begins with a group of people who are expert at looking: the professional searchers known as radiologists.

TRAFTON DREW: If you watch radiologists do what they do, I was absolutely convinced that they are like superhuman.

SPIEGEL: This is a Harvard researcher named Trafton Drew. And about three years ago, he started watching radiologists do their work. For hours, he would stand in their dark viewing rooms, in awe that they could so easily see in the images before them things that to him were simply invisible.

DREW: These tiny little nodules that I can't even see when people point to them. You know, they're just in a different world in terms of finding this very, very hard to fine thing.

SPIEGEL: But radiologists still sometimes fail to see important things. And Drew, who studies visual attention at Harvard, wanted to understand more. Now, because of his work in this field, Drew was naturally familiar with one of the most famous studies in the field of attention research: The Invisible Gorilla experiment.

(SOUNDBITE OF A VIDEO)

DANIEL SIMONS: This video is from research by Daniel Simons and Christopher Chabris...

SPIEGEL: That's psychologist Daniel Simons introducing the video that's used in the study. Before the video begin, viewers are told that they will see two groups of kids passing a basketball back and forth. And they're told to do one thing and one thing only.

(SOUNDBITE OF A VIDEO)

SIMONS: Count how many times the players wearing white pass the ball.

SPIEGEL: Drew says this is actually quite hard because the players are constantly moving around.

DREW: You'd have to really think, you know, you're counting in your head - one, two, three, four, five. And as you're counting that, a gorilla wanders onto the screen, looks straight ahead, beats his chest and walks off the screen - 19, 20.

SPIEGEL: Then the viewer is asked...

(SOUNDBITE OF A VIDEO)

SIMONS: Did you see the gorilla?

DREW: Sounds ridiculous, right? There's a gorilla on the screen, of course you're going to see it. But 50 percent of people miss the gorilla.

SPIEGEL: This is because when you ask someone to perform a challenging task, without realizing it, their attention narrows and can block out other things - even huge, hairy gorillas that appeared directly in front of them.

Which brings us back to the expert lookers: the radiologists. Trafton Drew wondered if somehow being so well trained in searching would make them immune to missing large, hairy gorillas.

DREW: You might expect that because they're experts, they would notice if something unusual was there.

SPIEGEL: And so, he took a picture of a man in gorilla.

DREW: It's not an actual gorilla. It's a man in a gorilla suit. But he's shaking his fist angrily.

SPIEGEL: And he superimposed that image on a series of the slides that radiologists typically look at when they're searching for cancer. Then he asked a bunch of radiologists to review the slides for cancerous nodules. He wanted to see if they would notice a gorilla the size of a matchbook glaring angrily at them from inside the slide - but they didn't.

DREW: Eighty-three percent of the radiologists did not see the gorilla.

SPIEGEL: Now, it wasn't because that the eyes of the radiologists didn't happen to fall on the large angry gorilla. The problem was in a way their brains had framed what they were doing. They were looking for cancer, not gorillas. And so...

DREW: They look right at it, but because they're not looking for a gorilla, they don't see that it's a gorilla.

SPIEGEL: In other words, what we're focused on filters the world around us so aggressively that it literally shapes what we see. And so, Drew says, we need to think really carefully about the instructions that we give to professional searchers, like radiologists or people looking for terrorist activity. Because what we tell them to look for will in part determine what they see and don't see.

Drew and his co-author Jeremy Wolfe are doing more studies, looking at how to help radiologists and other people see both visually and cognitively the things that hide in plain sight.

Alix Spiegel, NPR News, Washington. Transcript provided by NPR, Copyright NPR.