Thursday, September 4, 2014

(Literally) blind experts

An American friend drew my attention recently to a paper published last year and entitled The Invisible Gorilla Strikes Again: Sustained Inattentional Blindness in Expert Observers. It is the report of a study in which experts failed to detect an unexpected occurrence (gorilla) in their area of expertise even when viewing it directly.

This phenomenon, known for a long time and, to my knowledge, first described in a paper published in 1999 by Simons andChabris, is known as inattentional blindness. In the past, it has been demonstrated with naïve subjects in unfamiliar tasks. The authors of the above study asked: does inattentional blindness also occur frequently among experts?

A very interesting and highly relevant question!

To study this, they asked 24 radiologists (hence experts) to screen CT (Computed Tomography) scans of lungs for nodules. The radiologists ranged in age from 28 – 70 years; hence some must have had very considerable experience. Their eye movements were tracked as they viewed the scans. But embedded in the scans was a gorilla which was some 48 times the size of the average lung nodule that the radiologists were searching for; moreover, it was positioned close to a nodule.

20 of the 24 experts did not report seeing the gorilla and eye tracking revealed that, of the 20 radiologists who did not report seeing the gorilla, 12 had looked directly at where the gorilla was located.

The authors conclude that, “This is a clear illustration that radiologists, though they are expert searchers, are not immune to the effects of IB [inattentional blindness] even when searching medical images within their domain of expertise”. They add, “Presumably, they would have done much better at detecting the gorilla had they been told to be prepared for such a target…perhaps a smaller gorilla would have been more frequently detected because it would have been more closely matched the size of the lung modules” [sic].

A sobering thought!

I imagine that, on the whole, radiologists do end up detecting the nodules, even if they are apparently often not able to detect something that is blindingly obvious (if I may use the phrase in this context).

But just think of experts in other domains, say economics, and above all of expert politicians of all stripes and in all countries. Thinking about them, one cannot help but suppose that they, too, must suffer from inattentional blindness, but this time of a more cognitive variety.

In fact, I am increasingly inclined to believe that many of today’s problems are due to the inattentional blindness of politicians to the continual and rapid and huge changes occurring (and here the size of the gorilla compared to the lung nodules comes to mind). I am increasingly led to believe that politicians just do not have their ears to the ground and, in many instances, are – because of this inattentional blindness - way behind public opinion on a great many issues. Hence they are not up to date experts.

Perhaps this puts the inattentional blindness of radiologists to huge gorillas embedded in the scans they are examining in perspective.