Radiologists Looking for Nodules in CT Scan Miss Dancing Gorilla Showing Perceptual Blindness

(Image: Trafton Drew, Melissa Vo, Jeremy Wolfe/Psychological Science via CBS News)

What do you see in this CT scan above? Seems to be a cross-section of a set of lungs, but is there anything else?

[Don't cheat by reading on too soon.]

Still stumped?

Well, here’s the explanation: The infamous “invisible gorilla” test conducted by psychologists Dan Simons and Christopher Chabris in 1999 has now been similarly tested on radiologists to see if they would notice anything strange in scans to which they’re frequently exposed.

More than 24 experts were asked to evaluate five different scans and in the final scan was a dancing gorilla 48 times larger than the average potentially cancerous nodule they might be looking for, according to CBS News. And many still missed it.

CBS reported that 20 out of the 24 credentialed radiologists were unable to spot the gorilla. The research by Harvard University post-doctoral fellow Trafton Drew, which will be published in the journal Psychological Science, even monitored eye movements of the radiologists and found they spent about 5.8 seconds looking the CT scan with the gorilla. Twelve of the radiologists who missed it actually looked right at it.

On the flip side, those with no medical expertise were asked to look at the scans. None of these people spotted the gorilla. Other non-experts were told to announce if they saw a gorilla specifically — so they had prior knowledge that it might be in there. This group was able to spot the gorilla 88 percent of the time, CBS reported.

According to the Association for Psychological Science’s Wray Herbert, the study raises a “disturbing possibility” that experts might have “perceptual blindness.”

“They wanted to see if the radiologists, focused on the telltale nodules, would be blind to the easily detectable and highly anomalous gorilla,” Psychological Science noted.

Although the radiologists proved better off in spotting the gorilla — and nodules — than non-experts, Herbert said this is a “small comfort that the experts outperformed the average man on the street.”

“But there is no way around the main finding, which is that 83 percent of these highly trained physicians missed what might have been a life-threatening anomaly,” Herbert wrote.

If you are unfamiliar with the invisible gorilla test, try it out in this video (although since you know ahead of time it might not work as well):

(H/T: Daily Mail)