Do you see what I see?

Let’s play a very simple game of Where’s Waldo. It’s so simple I won’t even tell you what you’re looking for – although what you’re looking at is a CT image of someone’s lungs. Ready?

That's not a tumor, it's a.... © Psychological Science, 2013.

That’s not a tumor, it’s a…. © Psychological Science, 2013.

If you’re an experienced radiologist, you might have noticed a problematic nodule in there somewhere. For everyone else, the only obvious thing to pop out is the gorilla. Yes, a gorilla, because invisible gorillas are just too compelling to replace.

As obvious as that gorilla seems just sitting there in a single frame, it is incredibly difficult to spot when viewing these images the way that radiologists normally do: in “stacks” of several hundred slices, to encompass the entire chest cavity. When these scans are life-sized, that gorilla is the size of a matchbook. And yet, 83% of experienced radiologists hunting for lung nodules failed to spot the gorilla. Half of them looked at it, mind, eyes clearly fixated on that spot for about half a second, but they went on to say there was nothing unusual about that slice.

The good news is that you shouldn’t fire your radiologist just yet. An 83% failure rate may sound dismal, but it’s still better than the 100% failure rate of college students with only 10 minutes of training in lung nodule detection. And, of course, the radiologists also spotted far more nodules, too.

The lesson for doctors, and all of us: when you’re looking for one specific thing, you aren’t likely to notice something else, even if it’s as obvious as a gorilla in a lung, and even if your eyes look directly at it. This is the best illustration I can imagine for the importance of keeping an open mind.
Drew, T., Võ, M.L., & Wolfe, J.M. (2013). The invisible gorilla strikes again: Sustained inattentional blindness in expert observers. Psychological Science PMID: 23863753


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