The Invisible Gorilla: And Other Ways Our Intuition Deceives Us. Christopher Chabris
gorilla had gone unnoticed, at least in part, because it didn’t really stand out: It was dark-colored, like the players wearing black. Our belief that a distinctive object should “pop out” overrode our knowledge of the phenomenon of inattentional blindness. This “red gorilla” experiment shows that when something is unexpected, distinctiveness does not at all guarantee that we will notice it.
Reflective clothing helps increase visibility for motorcyclists, but it doesn’t override our expectations. Motorcyclists are analogous to the cross in this experiment. People fail to see them, but not just because they are smaller or less distinctive than the other vehicles on the road. They fail to see the motorcycles precisely because they stand out. Wearing highly visible clothing is better than wearing invisible clothing (and less of a technological challenge), but increasing the visual distinctiveness of the rider might be of limited use in helping drivers notice motorcyclists. Ironically, what likely would work to increase detection of motorcycles is to make them look more like cars. For example, giving motorcycles two headlights separated as much as possible, to resemble the visual pattern of a car’s headlights, could well increase their detectability.
There is one proven way to eliminate inattentional blindness, though: Make the unexpected object or event less unexpected. Accidents with bicyclists and pedestrians are much like motorcycle accidents in that car drivers often hit the bikers or walkers without ever seeing them. Peter Jacobsen, a public health consultant in California, examined the rates of accidents involving cars and either pedestrians or bicyclists across a range of cities in California and in a number of European countries.28 For each city, he collected data on the number of injuries or fatalities per million kilometers people traveled by biking and by walking in the year 2000. The pattern was clear, and surprising: Walking and biking were the least dangerous in the cities where they were done the most, and the most dangerous where they were done the least.
Why are motorists less likely to hit pedestrians or bicyclists where there are more people bicycling or walking? Because they are more used to seeing pedestrians. Think of it this way: Would you be safer crossing the pedestrian-clogged streets of London, where drivers are used to seeing people swarm around cars, or the wide, almost suburban boulevards of Los Angeles, where drivers are less accustomed to people popping up right in front of their cars without warning? Jacobsen’s data show that if you were to move to a town with twice as many pedestrians, you would reduce your chance of being hit by a car while walking by one-third.
In one of the most striking demonstrations of the power of expectations,29 Steve Most, who led the “red gorilla” study, and his colleague Robert Astur of the Olin Neuropsychiatry Research Center in Hartford, Connecticut, conducted an experiment using a driving simulator. Just before arriving at each intersection, subjects looked for a blue arrow that indicated which way they should turn, and they ignored yellow arrows. Just as subjects entered one of the intersections, a motorcycle unexpectedly drove right into their path and stopped. When the motorcycle was blue, the same color as the attended direction arrows, almost all of the drivers noticed it. When it was yellow, matching the ignored direction arrows, 36 percent of them hit the motorcycle, and two of them failed to apply their brakes at all! Your moment-to-moment expectations, more than the visual distinctiveness of the object, determine what you see—and what you miss.
Of course, not every automobile-versus-motorcycle collision is entirely the fault of the person driving the car. In the Ben Roethlisberger accident, the driver and the rider both had green lights, but Roethlisberger was going straight and had the right-of-way. A witness at the scene quoted Martha Fleishman, the driver of the car, as saying, “I was watching him approach but he was not looking at me.”30 Roethlisberger might never have seen Fleishman’s car, even though it was right in front of him. Had he seen it, he might have been able to avoid the accident.
A Hard Landing
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