“Inattentional Blindness” Illusion

Here’s an interesting study that was performed recently on a group of 24 qualified radiologists. Each was given a series of CT scans showing diseased lungs and was told to locate 10 abnormal nodules, or white lesions on the image below. Before I continue, let’s see if you are able to spot something abnormal in the provided CT scan?

Surprisingly, the last scan this group was shown included an image of a dancing gorilla (48 times larger than the nodules they were looking for!) A staggering 83% of these qualified practitioners missed it, despite looking at the scan four times on average. You’ve almost certainly seen the “Awareness Test” video we’ve featured before. It perfectly demonstrated the theory of change blindness — a phenomenon which means we don’t see changes we’re not expecting.

Researchers also determined by eye-tracking that radiologists spent 5.8 seconds looking at the scan with the gorilla, and out of the 20 radiologists who did not see the gorilla, 12 had looked directly at it” – said one of the scientists conducting the study.

According to the study the radiologists were suffering from “inattentional blindness”, a psychological phenomenon which occurs when ones brain is focused on a task and only registers what the mind considers important, or part of the job at hand.

Once the radiologists had been told that there was a gorilla somewhere in the sequence of scans they all found it immediately. Perhaps even more worrying than their inability to spot a silverback gorilla amongst the nodules is the fact that only 55 per cent of those studied were able to correctly identify all the lung abnormalities on the various scans… And they were actually looking for them!

39 Replies to ““Inattentional Blindness” Illusion”

  1. The first thing I saw was the gorilla. Interesting. Granted, I’m not a radiologist… and I didn’t read any of the text first!

  2. At first I thought the gorilla was in the silhouette or part of the whiteness in the middle mostly because so many illusions are like that on this site.

    Only after looking there for a minute or two I started to look elsewhere and saw it right away.

    The radiologists would be mostly looking at the outer layer and it’s scary that that didn’t stand out to them regardless of what they were looking for.

  3. This is an incorrect illusion. Even after I spotted the gorilla, I thought it is a trademark or something like that. Our eyes are accustomed to ignore such trademarks. Thus the gorilla just looks like something unusual.

  4. It looks like a ghost to me; if it’s a gorilla, it has awfully spindly arms, unless I’m looking at the wrong thing.

    1. @Annie: Yes, I think you looked at the wrong thing. The Gorilla is a tiny black figure in the upper right quadrant of the picture. D’you see it now?

  5. “Researchers also determined by eye-tracking that radiologists spent 5.8 seconds looking at the scan with the *gorilla*, ”

  6. I spotted it fairly quickly, but I feel that if I wasn’t looking for “something abnormal” I wouldn’t have seen it.

  7. Finally-once I realised that it wasn’t in the middle, I saw it at once !!! Look in the top right ‘corner’ and you’ll see it immediate;y and wonder why you were so stupid :D

  8. Makes you wonder how many people died or were misdiagnosed as a result of doctors not taking the time or caring enough to study these sort of tests in the detail that is required…

    1. They didn’t just look at one image they scrolled back and forth with a fade in/out silhouette of a gorilla. It wasn’t this easy. And the trick is you are looking for something else– nodules, etc. That’s the whole point of the test, its selective vision. A gorilla in your chest that’s clearly fake is cast out because it isn’t what they’re looking for (which is real, actual disease).

  9. I clicked the “spot something abnormal” link which I guesses would bring me to a large version of the picture. It brought me to a category which was giving away what I should look for and immediately found it of course.

  10. Unless you’re participating in the experiment, this illusion is not supposed to work on you.

    It’s only an illusion if you’re one of the Radiologists who was told to find the abnormal nodules.

    Here, out of context, if you don’t see the gorilla very quickly (almost immediately), there’s probably something terribly wrong with your eyes or perception in general.

  11. I never would have seen it if Pinyot hadn’t posted top right. I work in a hospital and I guess I have just gotten used to looking for cancer nodules! I will have to pass this on to my radiologists

  12. It didn’t surprise me that radiologist missed it, they missed my tumor on 3 separate xrays. Dr showed me the xrays and I saw it.

  13. A practical example of this happens to me in the autumn when I’m in the forest picking berries or mushrooms. You can’t look both for mushrooms AND berries at the same time, only one at the time. Both needs concentration to find the good spots, and you just need to ignore the other. It’s frustrating.

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