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

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СКАЧАТЬ little experimental evidence to support the popular belief about multitasking, and we haven’t found any evidence that men are more prone than women to miss the gorilla. In fact, the main conclusion from studies of multitasking is that virtually nobody does it well: As a rule, it is more efficient to do tasks one at a time rather than simultaneously.⁴⁴

      It’s still possible—even reasonable—to suspect that people differ in their ability to focus attention on a primary task, but that this ability isn’t related to general intelligence or educational achievement. If individual differences in the ability to focus attention lead to differences in noticing unexpected objects, then people for whom the counting task is easier should be more likely to notice the gorilla—they are devoting fewer resources to the counting task and have more left over.

      Dan and his graduate student Melinda Jensen recently conducted an experiment to test exactly this hypothesis. They first measured how well people could do a computer-based tracking task like the one we used in the “red gorilla” experiment and then looked to see whether those who performed the task well were more likely to notice an unexpected object. They weren’t. Apparently, whether you detect unexpected objects and events doesn’t depend on your capacity for attention. Consistent with this conclusion, Dan and sports scientist Daniel Memmert, the researcher who tracked children’s eye movements while they watched the gorilla video, found that who noticed and who missed an unexpected object was unrelated to several basic measures of attention capacity. These findings have an important practical implication: Training people to improve their attention abilities may do nothing to help them detect unexpected objects. If an object is truly unexpected, people are unlikely to notice it no matter how good (or bad) they are at focusing attention.

      As far as we can tell, there are no such people as “noticers” and “missers”—at least, no people who consistently notice or consistently miss unexpected events in a variety of contexts and situations. There is one way, however, to predict how likely a person is to see the unexpected. But it is not a simple trait of the individual or a quality of the event; it is the combination of a fact about the individual and a fact about the situation in which the unexpected event occurs. Only seven people out of more than one thousand stopped to listen to Joshua Bell playing in the L’Enfant Plaza subway station. One had been to a concert Bell had given just three weeks earlier. Two of the remaining six were musicians themselves. Their expertise helped them recognize his skill—and the pieces he was playing—through the din. One, George Tindley, worked in a nearby Au Bon Pain restaurant. “You could tell in one second that this guy was good, that he was clearly a professional,” he told Weingarten. The other, John Picarello, said, “This was a superb violinist. I’ve never heard anyone of that caliber. He was technically proficient, with very good phrasing. He had a good fiddle, too, with a big, lush sound.”

      Experiments support this observation. Experienced basketball players are more likely to notice the gorilla in the original basketball-passing video than are novice basketball players. In contrast, team handball players are no more likely to notice unexpected objects even though they are experts in a team sport that places demands on attention comparable to those of basketball.⁴⁵ Expertise helps you notice unexpected events, but only when the event happens in the context of your expertise. Put experts in a situation where they have no special skill, and they are ordinary novices, taxing their attention just to keep up with the primary task. And no matter what the situation, experts are not immune to the illusory belief that people notice far more than they do. Gene Weingarten described John Picarello’s behavior as he watched Bell play: “On the video, you can see Picarello look around him now and then, almost bewildered. ‘Yeah, other people just were not getting it. It just wasn’t registering. That was baffling to me.’”

      How Many Doctors Does It Take…

      Even within their field of specialty, experts are not immune to inattentional blindness or the illusion of attention. Radiologists are medical specialists responsible for reading x-rays, CT scans, MRIs, and other images in order to detect and diagnose tumors and other abnormalities. Radiologists perform this visual detection task under controlled conditions every day of their careers. In the United States, their training involves four years of medical school, followed by up to five years in residency at a teaching hospital. Those who specialize in specific body systems spend another year or two in fellowship training. In total, they often have more than ten years of post-undergraduate training, followed by on-the-job experience in studying dozens of films each day. Despite their extensive training, radiologists can still miss subtle problems when they “read” medical images.

      Consider a recent case described by Frank Zwemer and his colleagues at the University of Rochester School of Medicine.⁴⁶ An ambulance brought a woman in her forties to the emergency room with severe vaginal bleeding. Doctors attempted to insert an intravenous line in a peripheral vein, but failed, so they instead inserted a central line via a catheter in the femoral vein, the largest vein in the groin. Getting the line in correctly requires also inserting a guidewire, which is removed once the line is in place.

      The line was introduced successfully, but due to an oversight, the physician neglected to remove the guidewire.⁴⁷ To address her blood loss, the patient was given transfusions, but she then developed difficulty breathing due to pulmonary edema (a swelling or fluid buildup in the lungs). She was intubated for respiratory support, and a chest x-ray was taken to confirm the diagnosis and make sure that the breathing tube was placed correctly. The ER doctor and the attending radiologist agreed on the diagnosis, but neither of them noticed the guidewire. The patient went next to the intensive care unit for several days of treatment, and after she improved she went to a standard unit. There she developed shortness of breath, which was caused by pulmonary embolism—a blood clot in her lung. During this time she received two more x-rays, as well as an echocardiogram and a CT scan. Only on the fifth day of her stay in the hospital did a physician happen to notice and remove the guidewire while performing a procedure to correct the pulmonary embolism. The patient then made a full recovery. (It was determined later that the guidewire probably didn’t cause the embolism because it was constructed of so-called nonthrombogenic material specifically intended not to promote blood clotting.)

      When the various medical images were examined afterward, the guidewire was clearly visible on all three x-rays and on the CT, but none of the many doctors on the case noticed it. Their failure to see the anomalous guidewire illustrates yet again the dangers of inattentional blindness. The radiologists and other physicians who reviewed the chest images looked at them carefully, but they did not see the guidewire because they did not expect to see it.

      Radiologists have a tremendously difficult task. They often review a large number of images at a time, typically looking for a specific problem—a broken bone, a tumor, and so on. They can’t take in everything in the image, so they focus their attention on the critical aspects of the image, just as the subjects in the gorilla study focused on counting the passes of one team of players. Due to the limits of attention, radiologists are unlikely to notice aspects of the image that are unexpected, like the presence of a guidewire. But people assume that radiologists should notice any problem in a medical image regardless of whether it is expected; any failure to do so must therefore be the result of the doctor’s negligence. Radiologists are regularly sued for missing small tumors or other problems.⁴⁸ These lawsuits are often based on the illusion of attention—people assume that radiologists will notice anything anomalous in an image, when in reality they, like the rest of us, tend to see best what they are looking for in the image. If you tell radiologists to find the guidewire in a chest x-ray, they will expect to see one and will notice it. But if you tell them to find a pulmonary embolism, they may not notice the guidewire. (It’s also possible that when searching for the guidewire, they will miss more pulmonary embolisms.) An unexpected СКАЧАТЬ