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By on February 15, 2013, with 39 Comments

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.

Inattentional Blindness Illusion

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 Responses
  1. cgimusic says:

    Saw it pretty quickly but if it weren’t for the title I might not have.

  2. Dave says:

    I stared for a while without seeing it. Once you see it you wonder how you couldn’t see it right away! Thanks

  3. Shaun says:

    There is some monkey business going on here.

  4. Chris says:

    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!

  5. ? says:

    I did not see it straight away but then soon after I saw it

  6. Micah says:

    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.

  7. z2d4th says:

    I’ve seen it already on my first glance

  8. Lucci says:

    Saw it in about 3 seconds.

  9. Lucci says:

    I saw it in about 3 seconds.

  10. Eric says:

    When I read “dancing gorilla’, there it was!
    Before that, nothing!

  11. Som says:

    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.

  12. Annie says:

    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.

    • mylos says:

      @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?

  13. Vincent says:

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

  14. membersound says:

    what the f… this is awesome and disturbing at once

  15. Blessed_are_the_poor says:

    No wonder I keep coughing up hairballs

  16. Pinyot says:

    Top right

  17. Big Band Singer says:

    I’ve studied it for 15 min and still don’t see a dancing gorilla.

  18. illusionist says:

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

  19. Annie says:

    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

  20. Trish Willy says:

    I can’t see it, I’ve looked at this for a couple of days now.

  21. Big Band Singer says:

    Thanks to Pinyot, I finally see it. I was looking for something much larger, LOL.

  22. Ko says:

    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…

    • radiologist says:

      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).

  23. Josh says:

    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.

  24. Cyphis says:

    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.

  25. Ant says:

    I don’t see it. :(

  26. Patricia Willson says:

    I see it now thanks

  27. Nancy says:

    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

  28. Judy says:

    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.

  29. Sasa says:

    What Dr. House said?

  30. Olttonen says:

    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.

  31. The Doctor says:

    When I was viewing this, I was leaning with my head on my table, so the gorilla’s area was darkened.

  32. suor de sapo says:

    A catchy find Waldo one? Not my type of OI. Interesting study, though…

  33. stardragon says:

    I didn’t see a gorilla. I saw a lady with a huge leaf shaped head, leaf fingers, and a dress.

  34. Sophia says:

    The gorilla was the first thing I saw.

  35. kiana says:

    it looks like its rockin out XD top right small by the way

  36. Derpy says:

    Theres some monkey business going on in those lungs.

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