The Invisible Gorilla: And Other Ways Our Intuition Deceives Us. Christopher Chabris
this chapter, when we talk about looking, as in “looking without seeing,” we don’t mean anything abstract or vague or metaphorical. We literally mean looking right at something. We truly are arguing that directing our eyes at something does not guarantee that we will consciously see it. A skeptic might question whether a subject in the gorilla experiment or an officer chasing a suspect or a submarine commander bringing his ship to the surface actually looked right at the unexpected object or event. To perform these tasks, though (to count the passes, pursue a suspect, or sweep the area for ships), they needed to look right where the unexpected object appeared. It turns out that there is a way, in a laboratory situation at least, to measure exactly where on a screen a person fixates their eyes (a technical way of saying “where they are looking”) at any moment. This technique, which uses a device called an “eye tracker,” can provide a continuous trace showing where and for how long a subject is looking during any period of time—such as the time of watching the gorilla video. Sports scientist Daniel Memmert of Heidelberg University ran our gorilla experiment using his eye tracker and found that the subjects who failed to notice the gorilla had spent, on average, a full second looking right at it—the same amount of time as those who did see it!23
Ben Roethlisberger’s Worst Interception
In February 2006, at the age of twenty-three and in just his second season as a professional football player, Ben Roethlisberger became the youngest quarterback in NFL history to win a Super Bowl. During the off-season, on June 12 of that same year, he was riding his black 2005 Suzuki motorcycle heading outbound from downtown Pittsburgh on Second Avenue.24 As he neared the intersection at Tenth Street, a Chrysler New Yorker driven by Martha Fleishman approached in the opposite direction on Second Avenue. Both vehicles had green lights when Fleishman then turned left onto Tenth Street, cutting off Roethlisberger’s motorcycle. According to witnesses, Roethlisberger was thrown from his motorcycle, hit the Chrysler’s windshield, tumbled over the roof and off the trunk, and finally landed on the street. His jaw and nose were broken, many of his teeth were knocked out, and he received a large laceration on the back of his head, as well as a number of other minor injuries. He required seven hours of emergency surgery, but considering that he wasn’t wearing a helmet, he was lucky to survive the crash at all. Fleishman had a nearly perfect driving record—the only mark against her was a speeding ticket nine years earlier. Roethlisberger was cited for not wearing a helmet and for driving without the right type of license; Fleishman was cited and fined for failing to yield. Roethlisberger eventually made a full recovery from the accident and was ready to resume his role as the starting quarterback by the season opener in September.
Accidents like this one are unfortunately common. More than half of all motorcycle accidents are collisions with another vehicle. Nearly 65 percent of those happen much like Roethlisberger’s—a car violates the motorcycle’s right-of-way, turning left in front of the motorcyclist (or turning right in countries where cars drive on the left side of the road).25 In some cases, the car turns across oncoming traffic onto a side street. In others, the car turns across a lane of traffic onto the main street. In the typical accident of this sort, the driver of the car often says something like, “I signaled to turn left, and started out when it was clear. Then something hit my car and I later saw the motorcycle and the guy lying in the street. I never saw him!” The motorcyclist in such accidents says, “All of a sudden this car pulled out in front of me. The driver was looking right at me.” This experience leads some motorcyclists to assume that car drivers violate their right-of-way intentionally—that they see the motorcyclist and turn anyway.
Why do drivers turn in front of motorcyclists? We favor, at least for some cases, an explanation that appeals to the illusion of attention. People don’t see the motorcyclists because they aren’t looking for motorcyclists. If you are trying to make a difficult left turn across traffic, most of the vehicles blocking your path are cars, not motorcycles (or bicycles, or horses, or rickshaws…). To some extent, then, motorcycles are unexpected. Much like the subjects in our gorilla experiment, drivers often fail to notice unexpected events, even ones that are important. Critically, though, they assume they will notice—that as long as they are looking in the right direction, unexpected objects and events will grab their attention.
How can we remedy this situation? Motorcycle safety advocates propose a number of solutions, most of which we think are doomed to fail. Posting signs that implore people to “look for motorcycles” might lead drivers to adjust their expectations and become more likely to notice a motorcycle appearing shortly after the sign. Yet, after a few minutes of not seeing any motorcycles, their visual expectations will reset, leading them to again expect what they see most commonly—cars. Such advertising campaigns assume that the mechanisms of attention are permeable, subject to influence from our intentions and thoughts. Yet, the wiring of our visual expectations is almost entirely insulated from our conscious control. As we will discuss extensively in Chapter 4, our brains are built to detect patterns automatically, and the pattern we experience when driving features a preponderance of cars and a dearth of motorcycles. In other words, the ad campaign itself falls prey to the illusion of attention.
Suppose that one morning, we told you to watch for gorillas. Then, at some point a week later, you participated in our gorilla experiment. Do you think our warning would have any effect? Most likely not; in the time between the warning and the experiment, your expectations would have been reset by your daily experience of seeing no gorillas. The warning would only be useful if we gave it shortly before showing you the video.
Only when people regularly look for and expect motorcycles will they be more likely to notice. In fact, a detailed analysis of sixty-two accident reports involving cars and motorcycles found that none of the car drivers had any experience riding motorcycles themselves.26 Perhaps the experience of riding a motorcycle can mitigate the effects of inattentional blindness for motorcycles. Or, put another way, the experience of being unexpected yourself might make you better able to notice similar unexpected events.
Another common recommendation to improve the safety of motorcycles is for riders to wear bright clothing rather than the typical attire of leather jacket, dark pants, and boots. The intuition seems right: A yellow jumpsuit should make the rider more visually distinctive and easier to notice. But as we’ve noted, looking is not the same as seeing. You can look right at the gorilla—or at a motorcycle—without seeing it. If the gorilla or motorcycle were physically imperceptible, that would be trivially true—nobody would be surprised if you failed to see a gorilla that was perfectly camouflaged in a scene. What makes the evidence for inattentional blindness important and counterintuitive is that the gorilla is so obvious once you know it is there. So looking is necessary for seeing—if you don’t look at it, you can’t possibly see it. But looking is not sufficient for seeing—looking at something doesn’t guarantee that you will notice it. Wearing conspicuous clothing and riding a brightly colored motorcycle will increase your visibility, making it easier for people who are looking for you to see you. Such bright clothing doesn’t guarantee that you will be noticed, though.
We did not always realize this ourselves. When we first designed the gorilla experiment, we assumed that making the “gorilla” more distinctive would lead to greater detection—of course people would notice a bright red gorilla. Given the rarity of red gorilla suits, we and our colleagues Steve Most (then a graduate student in Dan’s lab and now a professor at the University of Delaware) and Brian Scholl (then a postdoctoral fellow in the psychology department and now a professor at Yale) created a computerized version of the “gorilla” video in which the players were replaced by letters and the gorilla was replaced by a red cross (+) that unexpectedly traversed the display.27 Subjects counted how many times the white letters touched the sides of the display window while ignoring the black letters.
Even jaded researchers like us were surprised by the result: 30 percent of viewers missed the bright red cross, even though it was the only cross, the only colored object, and the only