In the new study, Drew asked 24 radiologists to do a typical lung cancer screening using the CT scans of five patients. This requires the radiologist to sit at a computer and look for small white blobs on hundreds of X-rays, each showing a slightly different slice of the patient’s lung. “It’s incredible to watch them do this,” Drew says. “They go through these things in under three minutes.”

The researchers didn’t do anything tricky to the images from the first four patients, which included on the order of 1,000 scans. But hidden in the stack of 239 images from the fifth patient, the researchers inserted 5 consecutive scans showing the cartoon gorilla. They were sneaky about it, too. On first appearance, the gorilla was 50 percent transparent. On the second it was 75 percent, and on the third fully visible. Then it faded back out on the last two scans.

Just 4 of the 24 radiologists reported seeing the gorilla. What’s more, the researchers had used eye-tracking technology to chart exactly where on the scans the participants had been looking. “The majority of them looked directly at the gorilla for extended periods of time. They just don’t see it,” he says.

Drew repeated the experiment with 25 adults who had no medical training. All of them missed the gorilla.

Like the 1999 gorilla study, this one worked because participants were intensely focused on a very difficult task. As you’d expect (and hope!), the radiologists in the study were far better at spotting the cancer nodules than were the non-experts, with success rates of 55 percent and 12 percent, respectively. And that’s why I doubt the findings have dire implications for medical science.