A new study reveals that radiological expertise does not protect against inattentional blindness, the missing of retrospectively obvious findings when attention is engaged elsewhere.

Researchers at the University of Utah (Salt Lake City, USA), Macquarie University (Sydney, Australia), and other institutions conducted a study involving 50 radiologists who were asked to evaluate seven different chest computerized tomography (CT) scans for suspected lung cancer; however, the seventh CT contained both a large (9.1 cm diameter) breast mass, as well as a lymphadenopathy. The researchers wanted to test whether expertise in radiology predicts inattentional blindness rates for unexpected abnormalities that were clinically relevant.

The results showed that when their attention was focused on searching for lung nodules, 66% of the radiologists did not detect the breast cancer mass, and 30% did not detect lymphadenopathy. But only 3% and 10% of radiologists, respectively, missed the same abnormalities in a follow-up study, in which they were asked to search for a broader range of abnormalities. Experience, primary task performance, nor search behavior predicted which radiologists missed the unexpected abnormalities. The study was published on November 20, 2020, in Psychonomic Bulletin & Review.

“We've known for a long time that many errors in radiology are retrospectively visible. This means if something goes wrong with a patient, you can often go back to the imaging for that patient and see that there were visible signs, say a lung nodule, on something like a chest CT,” said senior author Trafton Drew, PhD, of the University of Utah. “If you've searched through your whole apartment for your phone, you might assume you would have noticed your keys during that search. Our research suggests a reason why you will probably have to search again specifically for the keys.”

“Focusing narrowly on one task may cause radiologists to miss unexpected abnormalities; however, focused attention is probably beneficial when the abnormalities match the radiologist's expectations,” said lead author Lauren Williams, PhD, of the University of Utah. “Any changes to clinical process would need to find the balance between the two. Some possibilities might be a general assessment of a scan before looking for specific abnormalities, or using checklists to scan for commonly missed findings.”

The best known example of inattentional blindness is an experiment conducted at Harvard University in 1999 that asked participants to watch a video in which six people--three in white shirts and three in black shirts--pass basketballs around. Study participants were asked to count the number of passes. At some point, a gorilla strolls among them, faces the camera and thumps its chest, and then leaves, spending nine seconds on screen. The study revealed that half of the people who watched the video and counted the passes missed the gorilla.

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