The Invisible Gorilla

Have you ever wondered how tools and other paraphernalia can get left behind when a technician closes up a workspace? From the flashlight left in a nose wheel steering cable run to rags left in engines, the maintenance world is often left scratching its head trying to answer this question: How did a maintenance professional miss something so obvious?

Two researchers have an answer that explains not only how a technician can leave tools behind but also how a driver can fail to see a car right in front of him before an accident, how a policeman can run past a crime without noticing it and other confounding lapses in vision.

In the late 1990s, psychology researchers Christopher Chabris and Daniel Simons conducted an experiment at Harvard University. Dubbed “the invisible gorilla,” it asked participants to watch a short video in which six people—three wearing white shirts and three wearing black—pass basketballs back and forth. Participants were given one instruction: to count the number of passes made by those wearing white shirts.

Midway through the video, a student dressed in a gorilla suit walks into the middle of the circle of players, thumps his chest a few times and walks off stage. You’d think no one could miss anything so obvious, but an eye-popping 50% of those who took the test missed the gorilla. Since the original experiment, the test has been repeated in different conditions, with different audiences and in different countries, but the result is always the same. Focused on counting passes, per the instructions, about half the people miss the gorilla.

The experiment suggests that we miss a lot of what goes on around us. “We all believe that we are capable of seeing what’s in front of us,” say Chabris and Simons in their just-published book, The Invisible Gorilla (Crown, 2010). “But these intuitive beliefs are often mistaken ones that mask critically important limitations on our cognitive abilities.”

Everyone Is Affected

How is it that fully half of us can miss something so obvious? It’s not a vision problem—it’s an attention problem. It’s an error in perception resulting from a lack of attention to an unexpected object. The scientific name for this is “inattentional blindness.”

“When people devote their attention to a particular area or aspect of their visual world, they tend not to notice unexpected objects, even when those unexpected objects are salient, potentially important and appear right where they are looking,” say Chabris and Simons.

In other words, when a technician is focused on the individual items on a checklist, it is entirely possible that he could miss something not specifically on that checklist—even when that “something” is a bright red rag lying in his field of vision. He may think that he is paying full attention to his work—and that may be true to some extent—but as the researchers have discovered, attention is an “illusion.” Moreover, our “distorted beliefs” about it, they add, are “not just wrong, but wrong in dangerous ways.”

Managers can help eliminate inattentional blindness by heightening awareness. During your next human factors training session, show your technicians the “invisible gorilla” video (available for free at www.theinvisiblegorilla.com) and find out what percentage miss the gorilla. Use the results as a springboard for discussion.

“Looking is necessary for seeing,” conclude Chabris and Simons. “But looking is not sufficient for seeing.” That’s the shift technicians need to make—not just looking, but seeing. In particular, seeing the unexpected.