Читать книгу The Invisible Gorilla: And Other Ways Our Intuition Deceives Us - Christopher Chabris - Страница 10

NASA research scientist Richard Haines spent much of his career at Ames Research Center, a space and aeronautics think tank in northern California. He is best known publicly for his attempts to document UFO experiences. But in the late 1970s and early 1980s, he and his colleagues Edith Fischer and Toni Price conducted a pioneering study on pilots and information display technologies using a flight simulator.³¹ Their experiment is important because it is one of the most dramatic demonstrations of looking without seeing. They tested commercial airline pilots who were rated to fly the Boeing 727, one of the most common planes of the time. Commercial airline pilots tend to be among the most experienced and expert pilots—many flew in the military for years, and only the top pilots get to fly the larger commercial planes, where they have responsibility for hundreds of passengers on every flight. The subjects in this study were either first officers or captains who had flown 727s commercially for over one thousand hours.

During the experiment, the pilots underwent extensive training on the use of a “head-up display.” This technology, which was relatively new at the time, displayed much of the critical instrumentation needed to fly and land the simulated 727—altitude, bearing, speed, fuel status, and so on—in video form directly on the windshield in front of the pilots, rather than below or around it as in an ordinary cockpit. Over the course of multiple sessions, the pilots flew a number of simulated landings under a wide range of weather conditions, either with or without the head-up display. Once they were practiced with the simulator, Haines inserted a surprise into one of the landing trials. As the pilots broke through the cloud ceiling and the runway came into view, they prepared for landing as they had on all of the previous trials, monitoring their instruments and the weather conditions to decide whether or not to abort. In this case, however, some of them never saw the large jet on the ground turning onto the runway right in front of them.

Such “runway incursions”—which happen when planes enter runways when they shouldn’t—are among the more common causes of airplane accidents. More than half of the incursions result from pilot error—a pilot taxis into the path of another aircraft. Just as the USS Greeneville was exceptionally unlikely to surface into another ship, most runway incursions present little or no risk of a collision. In fiscal year 2007, the Federal Aviation Administration recorded a total of 370 runway incursions at American airports. In only 24 of them was there a significant potential for a collision, and only 8 of those involved commercial flights. Over the four years from 2004 through 2007, there were a total of 1,353 runway incursions in the United States, 112 of which were classified as serious, and only 1 of which resulted in a collision. That said, the single worst accident in aviation history involved a runway incursion. In 1977, in the Canary Islands, KLM flight 4805 took off down the runway and collided at full speed with Pan Am flight 1736, which was taxiing in the other direction on the same runway. The collision of these two Boeing 747s resulted in 583 deaths.

Although runway incursions are relatively common compared with other aviation accidents, airplane collisions of every sort are exceptionally rare. With only eight runway incursions out of more than 25 million flights in 2007, you would need to take an average of one commercial round-trip flight every day for about three thousand years to have a more than even chance of encountering a serious runway incursion. These incidents are relatively common, with the key word being “relatively.” They are still exceedingly rare—and consequently, they are unexpected.³²

What’s surprising about Haines’s flight simulator experiment is that the head-up display should—or at least our intuition suggests that it should—have kept the pilots’ attention on the place where the parked plane was going to appear. They never had to look away from the runway to see their instruments. But two of the pilots using the head-up display would have plowed right through the plane on the runway had the experimenter not aborted the trial. The plane was clearly visible just seconds after the pilots cleared the clouds, and they had about seven more seconds to safely abort their landing. The pilots using the head-up display were also slower to respond, and when they tried to execute a “missed approach” (by pulling up to go around and make a new landing attempt), they were late in doing so. The two who didn’t manage to abort their landings in time were both rated either good or excellent in their simulator flying performance. When the trial was over, Haines asked them whether they saw anything, and both said no. After the experiment, Haines showed the pilots a videotape of the landing with the airplane stationed in their path, and both expressed surprise and concern that they had missed something so obvious. One said, “If I didn’t see [the tape], I wouldn’t believe it. I honestly didn’t see anything on that runway.”³³ The plane on the runway was their invisible gorilla—they didn’t expect it to be there, so they never saw it.

Now that we understand that looking is not seeing, we can see that the intuition that a head-up display will enhance our ability to detect unexpected events is wrong. Head-up displays can help in some respects: Pilots get faster access to relevant information from their instruments and need to spend less time searching for that information. In fact, flight performance can be somewhat better with a well-designed head-up display than without one. Using a so-called conformational display, which superimposes a graphical indication of the runway on top of the physical runway visible through the windshield, pilots can fly more precisely.³⁴ Although the head-up display helps pilots perform the task they are trying to accomplish (like landing a plane), it doesn’t help them see what they are not expecting to see, and it might even impair their ability to notice important events in the world around them.

How is it possible that spending more time with the world in view actually reduces our ability to see what is right in front of us? The answer, it seems, stems from our mistaken beliefs about how attention works. Although the plane on the runway was right in front of the pilots, fully in view, the pilots were focusing their attention on the task of landing the plane and not on the possibility of objects on the runway. Unless pilots inspect the runway to see if there are any obstructions, they are unlikely to see something unexpected, such as a plane taxiing onto their landing strip. Air traffic controllers are, after all, supposed to control the traffic to make sure that this doesn’t happen. If a failure to inspect the runway were the only factor in play, though, a head-up display would be no worse than looking away at your instruments and then back to the windshield. After all, in both cases, you could spend the same amount of time ignoring the runway. You either focus attention on the readings on the windshield or focus attention on the instruments surrounding the windshield. But as Haines’s study showed, pilots are slower to notice unexpected events when they are using a head-up display. The problem has to do not as much with the limits on attention—which are in effect regardless of whether the readings are displayed on the windshield or around it—as with our mistaken beliefs about attention.