The Invisible Gorilla: And Other Ways Our Intuition Deceives Us. Christopher Chabris
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.
Hold All Calls, Please
Imagine that you are driving home from work, thinking about what you will do when you get there and everything you left unfinished at the office. Just as you begin to make a left turn across a lane of oncoming traffic, a boy chases a ball into the road in front of you. Would you notice him? Maybe not, you should now be thinking. What if, rather than being lost in thought while you were driving, you were talking on a cell phone? Would you notice then? Most people believe that as long as their eyes are on the road and their hands are on the wheel, they will see and react appropriately to any contingency. Yet extensive research has documented the dangers of driving while talking on a phone. Both experimental and epidemiological studies show that the driving impairments caused by talking on a cell phone are comparable to the effects of driving while legally intoxicated.35 When talking on a cell phone, drivers react more slowly to stoplights, take longer to initiate evasive maneuvers, and suffer from generally reduced awareness of their surroundings. In most cases, neither drunk driving nor driving while talking on a cell phone lead to accidents. In part, that is because most driving is predictable and lawful, and even if you aren’t driving perfectly, the other drivers are trying not to hit you. The situations in which such impairments are catastrophic, though, are those that require an emergency reaction to an unexpected event. A slight delay in braking might make the difference between stopping short of the boy in the street and running him over.
For the most part, people are at least familiar with the dangers of talking on a cell phone while driving. We’ve all seen distracted drivers run a stop sign, obliviously veer into another lane, or drive at 30 mph in a 45 mph zone. As columnist Ellen Goodman wrote, “The very same people who use cell phones…are convinced that they should be taken out of the hands of (other) idiots who use them.”36
The realization that (other) people are unable to drive safely while talking on the phone led to a movement to regulate the use of handheld cell phones while driving. New York was one of the first states to pass such legislation. The law banned the use of handheld phones while driving, based on the intuition that taking our hands off the wheel to use the phone is the main danger posed by talking while driving. In fact, the New York legislation provided for tickets to be waived if drivers could prove that they subsequently purchased a hands-free headset. Not surprisingly, the telecommunications industry supported the New York bill and regularly promotes the safety and advantages of hands-free headsets. A flier from AT&T Wireless proclaims, “If you use your wireless phone while driving, you can keep both hands on the wheel,” and a similar brochure from Nokia ranks using a hands-free device whenever possible as second on their list of ten safety recommendations. In our survey, 77 percent of Americans agreed with the statement, “While driving, it’s safer to talk on a hands-free phone than a handheld phone.” The assumption underlying these beliefs and claims as well as most laws on distracted driving—that as long as you are looking at the road, you will notice unexpected events—is precisely the illusion of attention. Given what you now know about the gorilla experiment, you can probably guess what we will say next.
The problem isn’t with our eyes or our hands. We can drive just fine with one hand on the wheel, and we can look at the road while holding a phone. Indeed, the acts of holding a phone and turning a steering wheel place little demand on our cognitive capacities. These motor-control processes are almost entirely automatic and unconscious; as an experienced driver, you don’t have to think about how to move your arms to make the car turn left or to keep the phone up to your ear. The problem is not with limitations on motor control, but with limitations on attentional resources and awareness. In fact, there are few if any differences between the distracting effects of handheld phones and hands-free phones. Both distract in the same way, and to the same extent.37 Driving a car and having a conversation on a cell phone, despite being well-practiced and seemingly effortless tasks, both draw upon the mind’s limited stock of attention resources. They require multitasking, and despite what you may have heard or may think, the more attention-demanding tasks your brain does, the worse it does each one.
In a second part of our original gorilla experiment, we tested the limits of attention by making the task of the subjects (counting basketball passes) more difficult. Rather than just a single count of the total number of passes made by the white team, we asked people to keep two separate mental counts, one of aerial passes and one of bounce passes (but still focusing on the white team). As we predicted, this increased by 20 percent the number of people missing an unexpected event.38 Making the counting task harder requires people to devote more attention to it, leaving fewer mental resources available to see the gorilla. As we use more of our limited attention, we are that much less likely to notice the unexpected. The problem is with consuming a limited cognitive resource, not with holding the phone. And most important, as the incredulous reactions of our study participants demonstrate, most of us are utterly unaware of this limit on our awareness. Experiment after experiment has shown no benefit whatsoever for hands-free phones over handheld ones. In fact, legislation banning the use of handheld phones might even have the ironic effect of making people more confident that they can safely use a hands-free phone while driving.
One could argue that our gorilla experiment isn’t really comparable to the scenario of driving while talking on a cell phone. That is, increasing the difficulty of the counting task as we did might increase the