This is one for all the Behavior-Based Safety Observation admirers who somehow convinced themselves their BBS process is flawless. Most of us in the safety profession has seen the “gorilla and basketball” video. The study used a video made famous by earlier “inattention blindness” research featured in the 2010 book “The Invisible Gorilla,” by Christopher Chabris, a psychologist at Union College in Schenectady, N.Y., and Daniel Simons, a psychologist at the University of Illinois at Urbana-Champaign. The video shows six people passing a basketball. Viewers are asked to count the number of passes made. Many people are so intent on counting that they fail to see a person in a gorilla suit stroll across the scene, stop briefly to thump their chest, and then walk off.
We like to think that we would notice the occurrence of an unexpected yet salient event in our world. However, we know that people often miss such events if they are engaged in a different task, a phenomenon known as “inattentional blindness.” Still, these demonstrations typically involve naïve observers engaged in an unfamiliar task. What about expert searchers who have spent years honing their ability to detect small abnormalities in specific types of images?
We asked 24 radiologists to perform a familiar lung nodule detection task. A gorilla, 48 times larger than the average nodule, was inserted in the last case. 83% of radiologists did not see the gorilla. Eye-tracking revealed that the majority of those who missed the gorilla looked directly at the location of the gorilla. Even expert searchers, operating in their domain of expertise, are vulnerable to inattentional blindness.
When engaged in a demanding task, attention can act like a set of blinders, making it possible for salient stimuli to pass unnoticed right in front of our eyes (Neisser & Becklen, 1975). This phenomenon of “sustained inattentional blindness” is best known from Simons and Chabris’ (1999) study in which observers attend to a ball-passing game while a human in a gorilla suit wanders through the game. Despite having walked through the center of the scene, the gorilla is not reported by a substantial portion of the observers.
Does inattentional blindness (IB) still occur when the observers are experts, highly trained on the primary task?
There is some evidence that expertise mitigates the effect. For example, Memmert (Memmert, 2006) found a decreased the rate of IB for basketball players who were asked to count the number of basketball passes in an artificial game. On the other hand, when Potchen (2006) showed radiologists chest x-rays with a clavicle (collarbone) removed, roughly 60% of radiologists failed to notice when they were reviewing cases as if for an annual exam. Finally, a recent observational case report documented a case where a misplaced femoral line was not detected by variety of health care professionals who evaluated the case (Lum, Fairbanks, Pennington, & Zwemer, 2005).
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