The Invisible Gorilla: And Other Ways Our Intuition Deceives Us. Christopher Chabris

Чтение книги онлайн.

СКАЧАТЬ in hindsight.

      Unfortunately, people often confuse what is easily noticed when it is expected with what should be noticed when it is unexpected. Moreover, the procedures frequently used in hospitals when reviewing radiographs are affected by the illusion of attention; doctors themselves also assume that they will notice unexpected problems in an image, even when they are looking for something else. To reduce the effects of inattentional blindness, one can deliberately reexamine the same images with an eye toward the unexpected. When participants in our studies know that something unexpected might happen, they consistently see the gorilla—the unexpected has become the target of focused attention. Devoting attention to the unexpected is not a cure-all, however. We have limited attention resources, and devoting some attention to unexpected events means that we have less attention available for our primary task. It would be imprudent to ask radiologists to take time and resources away from detecting the expected problem in an x-ray (“Doctor, can you confirm that this patient has a pulmonary embolism so that we can begin treatment?”) to focus instead on things that are unlikely to be there (“Doctor, can you tell us whether we left anything behind in this patient’s body?”). A more effective strategy would be for a second radiologist, unfamiliar with the case and the tentative diagnosis, to examine the images and to look for secondary problems that might not have been noticed the first time through.

      So it turns out that even experts with a decade of training in their medical specialty can miss unexpected objects in their domain of expertise. Although radiologists are better able than laypeople to detect unusual aspects of radiographs, they suffer from the same limits on attention as everyone else. Their expertise lies not in greater attention, but in more precise expectations formed by their experience and training in perceiving the important features of the images. Experience guides them to look for common problems rather than rare anomalies, and in most cases, that strategy is wise.

      What Can We Do About the Illusion of Attention?

      If this illusion of attention is so pervasive, how has our species survived to write about it? Why weren’t our would-be ancestors all eaten by unnoticed predators? In part, inattentional blindness and the accompanying illusion of attention are a consequence of modern society. Although our ancestors must have had similar limitations on awareness, in a less complex world there was less to be aware of. And few objects or events needed immediate attention. In contrast, the advance of technology has given us devices that require greater amounts of attention, more and more often, with shorter and shorter lead times. Our neurological circuits for vision and attention are built for pedestrian speeds, not for driving speeds. When you are walking, a delay of a few seconds in noticing an unexpected event is likely inconsequential. When you are driving, though, a delay of even one-tenth of a second in noticing an unexpected event can kill you (or someone else). The effects of inattention are amplified at high speeds, since any delay in noticing happens at the highest speed.

      The effects of inattention are further amplified by any device or activity that takes attention away from what we are trying to do. Such devices and activities were rare in the BlackBerryless, iPhone-free, pre-GPS past, but they’re common today. Fortunately, accidents are still rare, because most of the time, nothing unexpected happens. But it is those rare unexpected events that matter. People are confident that they can drive and talk on the phone simultaneously precisely because they almost never encounter evidence that they cannot. And by “evidence” we don’t mean a news story about accident rates or a safety institute’s latest report, or even a story of a friend who zoned out while driving and almost hit something. We mean a personal experience, like a collision or a near miss, that was unambiguously caused by a depletion of attention and that cannot be explained away as the other person’s fault (a rationalization we are as good at making as we are at overestimating our own levels of attention). We will almost never be aware of the more subtle evidence of our distraction. Drivers who make mistakes usually don’t notice them; after all, they’re distracted.

      The problem is that we lack positive evidence for our lack of attention. That is the basis of the illusion of attention. We are aware only of the unexpected objects we do notice, not the ones we have missed. Consequently, all the evidence we have is for good perception of our world. It takes an experience like missing the chest-thumping gorilla, which is hard to explain away (and which we have little incentive to explain away), to show us how much of the world around us we must be missing.

      If the mechanisms of attention are opaque to us, how can we eliminate inattentional blindness so that we can be sure to spot the gorilla? The answer isn’t simple. In order to eliminate inattentional blindness, we would effectively have to eliminate focused attention. We would have to watch the gorilla video without bothering to focus on counting passes or even to focus on what we found interesting in the display. We would have to watch the display without expectations and without goals. But for the human mind, expectations and goals are inextricably intertwined with the most basic processes of perception and are not readily extinguished. Expectations are based on our prior experiences of the world, and perception builds on that experience. Our experience and expectations help us to make sense of what we see, and without them, the visual world would just be an unstructured array of light, a “blooming, buzzing confusion” in the classic words of William James.⁴⁹

      For the human brain, attention is essentially a zero-sum game: If we pay more attention to one place, object, or event, we necessarily pay less attention to others. Inattentional blindness is thus a necessary, if unfortunate, by-product of the normal operation of attention and perception. If we are right that inattentional blindness results from inherent limits on the capacity of visual attention, it might be impossible to reduce or eliminate it in general. In essence, trying to eliminate inattentional blindness would be equivalent to asking people to try flying by flapping their arms really rapidly. The structure of the human body doesn’t permit us to fly, just as the structure of the mind doesn’t permit us to consciously perceive everything around us.

      The issue of how best to allocate our limited attention relates to a larger principle of attention. For the most part, inattentional blindness isn’t a problem. In fact, it is a consequence of the way attention works; it is the cost of our exceptional—and exceptionally useful—ability to focus our minds. Focused attention allows us to avoid distraction and use our limited resources more effectively; we don’t want to be distracted by everything else around us. Most drivers follow the rules of the road, most doctors don’t leave guidewires in patients, most fishing vessels aren’t floating right above submarines, most planes aren’t guided in to land right on top of other planes, most cops don’t viciously beat suspects, and most world-class violinists don’t play in the subway. And gorillas rarely saunter through basketball games. Unexpected events are unexpected for a good reason: They are rare. More important, in most cases, failing to spot the unexpected has little consequence.

      Attention Writ Large

      The illusion of attention affects us all in both mundane and potentially life-threatening ways—it truly is an everyday illusion. It contributes to everything from traffic accidents and airplane cockpit displays to cell phones, medicine, and even subway busking. As the gorilla experiment has become more widely known, it has been used to explain countless failures of awareness, from the concrete to the abstract, in diverse domains. It’s not just limited to visual attention, but applies equally well to all of our senses and even to broader patterns in the world around us. The gorilla experiment is powerful because it forces people to confront the illusion of attention. It provides an effective metaphor precisely because the illusion of attention has such broad reach. Here are some examples:⁵⁰

       A trainer uses it to show people how they can miss safety infractions that are right in front of them.

       A Harvard professor uses it to explain how discriminatory practices in the workplace СКАЧАТЬ