The Invisible Gorilla: And Other Ways Our Intuition Deceives Us

(#litres_trial_promo) 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.”

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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.

(#litres_trial_promo) 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.

(#litres_trial_promo) 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 burden on attention more than a cell phone conversation would. There’s an easy way to account for this possibility, though: Do an experiment! To explore the effects of cell phone conversations on inattention directly, Brian Scholl and his students at Yale used a variant of the “red gorilla” computerized task described earlier and compared a group who performed the task as usual with one that performed it while simultaneously carrying on a cell phone conversation.

(#litres_trial_promo) In their particular variant of the task, about 30 percent of the participants missed the unexpected object when they were just doing the tracking task. However, participants who performed the task while talking on a phone missed the unexpected object 90 percent of the time! Simply having a conversation on a phone tripled the chances that they would fail to see something unexpected.

This sobering finding shows that cell phone conversations dramatically impair visual perception and awareness. These impairments are due to the limits of attention and not due to the nature of the phone; even though both tasks seem effortless, both demand our attention. Intriguingly, the cell phone conversation didn’t impair the subjects’ ability to do the tracking task—it just decreased their chances of noticing something unexpected. This finding may explain why people falsely think that cell phones have no effect on their driving: People are lulled into thinking that they drive just fine because they can still perform the primary task (staying on the road) properly. The problem is that they’re much less likely to notice rare, unexpected, potentially catastrophic events, and our daily experience gives us little feedback about such events.

If you’re like many people who have heard us speak about inattention, cell phones, and driving, you may wonder why talking to someone on a phone should be any more dangerous than talking to the person in the passenger seat, which doesn’t seem objectionable. (Or, if you have responded enthusiastically to our arguments—and thank you for doing so—you may be getting ready for a campaign to make “driving while talking” illegal, no matter whom you are talking to.) It may come as a surprise, then, to learn that talking to a passenger in your car is not nearly as disruptive as talking on a cell phone. In fact, most of the evidence suggests that talking to a passenger has little or no effect on driving ability.

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Talking to a passenger could be less problematic for several reasons. First, it’s simply easier to hear and understand someone right next to you than someone on a phone, so you don’t need to exert as much effort just to keep up with the conversation. Second, the person sitting next to you provides another set of eyes—a passenger might notice something unexpected on the road and alert you, a service your cell-phone conversation partner can’t provide. The most interesting reason for this difference between cell-phone conversation partners and passengers has to do with the social demands of conversations. When you converse with the other people in your car, they are aware of the environment you are in. Consequently, if you enter a challenging driving situation and stop speaking, your passengers will quickly deduce the reason for your silence. There’s no social demand for you to keep speaking because the driving context adjusts the expectations of everyone in the car about social interaction. When talking on a cell phone, though, you feel a strong social demand to continue the conversation despite difficult driving conditions because your conversation partner has no reason to expect you to suddenly stop and start speaking. These three factors, in combination, help to explain why talking on a cell phone is particularly dangerous when driving, more so than many other forms of distraction.

For Whom Does Bell Toil?

All of the examples we have discussed so far show how we can fail to see what is right in front of us: A submarine captain fails to see a fishing vessel, a driver fails to notice a motorcyclist, a pilot fails to see a runway obstruction, and a Boston cop fails to see a beating. Such failures of awareness and the illusion of attention aren’t limited to the visual sense, though. People can experience inattentional deafness as well.

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In 2008, the Pulitzer Prize for Feature Writing went to Gene Weingarten for his Washington Post cover story describing a social “experiment” he conducted with the help of virtuoso violinist Joshua Bell.

(#litres_trial_promo) As a four-year-old in Indiana, Bell impressed his parents, both psychologists, by using rubber bands to pluck out songs he had heard. They engaged a series of music teachers and by age seventeen Bell had played Carnegie Hall. He was on his way to repeatedly topping the classical music charts, receiving numerous awards for his performances, and appearing on Sesame Street. The official biography on his website begins with these words: “Joshua Bell has captured the public’s attention like no other classical violinist of his time.”

On a Friday morning at rush hour, Bell took his Stradivarius violin, for which he’d paid more than $3 million, to the L’Enfant Plaza subway stop in Washington, D.C. He set up shop between an entrance and an escalator, opened his violin case to take donations, seeded it with some cash of his own, and began to perform several complex classical pieces. Over the course of his forty-three-minute performance, more than one thousand people passed within a few feet of him, but only seven stopped to listen. And not counting a donation of $20 from a passerby who recognized him, Bell made only $32.17 for his work.

Weingarten’s article bemoaned the lack of appreciation for beauty and art in modern society. Reading it, you can sense the pain and disappointment he must have felt while watching the people go past Bell:

It was all videotaped by a hidden camera. You can play the recording once or 15 times, and it never gets any easier to watch. Try speeding it up, and it becomes one of those herky-jerky World War I-era silent newsreels. The people scurry by in comical little hops and starts, cups of coffee in their hands, cellphones at their ears, ID tags slapping at their bellies, a grim danse macabre to indifference, inertia and the dingy, gray rush of modernity.

Fellow staffers at the Washington Post magazine apparently expected a different result. According to Weingarten’s story, they had been worried that the performance might cause a riot:

In a demographic as sophisticated as Washington, the thinking went, several people would surely recognize Bell. Nervous “what-if” scenarios abounded. As people gathered, what if others stopped just to see what the attraction was? Word would spread through the crowd. Cameras would flash. More people flock to the scene; rush-hour pedestrian traffic backs up; tempers flare; the National Guard is called; tear gas, rubber bullets, etc.

After the stunt was over, Weingarten asked famous conductor Leonard Slatkin, who directs the National Symphony Orchestra, to predict how a professional performer would do as a subway artist. Slatkin was convinced a crowd would gather: “Maybe 75 to 100 will stop and spend some time listening.” During the actual performance, less than one-tenth that number stopped, and the National Guard did not mobilize.

Weingarten, his editors, Slatkin, and perhaps the Pulitzer committee members fell prey to the illusion of attention. Even Bell, when he saw the video of his performance, was “surprised at the number of people who don’t pay attention at all, as if I’m invisible. Because, you know what? I’m makin’ a lot of noise!”

(#litres_trial_promo) Now that you’ve read about invisible gorillas, neglected fishing vessels, and unseen motorcycles, you can likely guess one reason why Bell went unrecognized for the great musician he is. People weren’t looking (or listening) for a virtuoso violinist. They were trying to get to work. The one person interviewed for the story who correctly understood the minimal response to Bell was Edna Souza, who shines shoes in the area and finds buskers distracting. She wasn’t surprised that people would rush by without listening: “People walk up the escalator, they look straight ahead. Mind your own business, eyes forward.”

Under the conditions Weingarten established, commuters were already engaged in the distracting task of rushing to get to work, making them unlikely to notice Bell at all, let alone focus enough attention on his playing to distinguish him from a run-of-the-mill street musician. And that is the key. Weingarten’s choice of time and location for the stunt nearly guaranteed that nobody would devote much attention to the quality of Bell’s music. Weingarten is concerned that “if we can’t take the time out of our lives to stay a moment and listen to one of the best musicians on Earth play some of the best music ever written; if the surge of modern life so overpowers us that we are deaf and blind to something like that—then what else are we missing?” Probably a lot, but this stunt provides no evidence for a lack of aesthetic appreciation. A more plausible explanation is that when people are focusing attention (visual and auditory) on one task—getting to work—they are unlikely to notice something unexpected—a brilliant violinist along the way.

If we were designing an experiment to test whether or not Washingtonians are willing to stop and appreciate beauty, we would first pick a time and location where an average street performer would attract an average number of listeners. We would then randomly place either a typical street performer or Joshua Bell there on several different days to see who earned more money. In other words, to show that people don’t appreciate beautiful music, you first have to show that at least some people are listening to it and then show that they reward it no more than they do average music. Weingarten wouldn’t have won a Pulitzer had he stationed Bell next to a jackhammer. Under those conditions, nobody would be surprised by the lack of attention to the musician—the deafening sound would have drowned out the violin. Placing Bell next to a subway station escalator during rush hour had the same effect, but for a different reason. People physically could have heard Bell playing, but because their attention was diverted by their morning commute, they suffered from inattentional deafness.

Other factors worked against Bell as well—he was performing relatively unfamiliar classical pieces rather than music that most commuters would know. If Bell had played The Four Seasons or other better-known classical pieces, he might have done better. By doing so, a far less talented musician could have taken in more money than Bell did. When Dan lived in Boston, he occasionally walked from downtown to the North End to get Italian food. At least half a dozen times, he walked past an accordion player who stationed himself at one end of an enclosed walkway that ran past a highway—a perfect place to attract listeners with time on their hands, walking to restaurants that they’d probably have to wait to get into anyhow. For street artists, like for real estate, location is everything. The accordionist played with gusto, showing an emotional attachment to his instrument and his art. Yet, Dan only ever heard him play one song: the theme from The Godfather. He played it when Dan walked to dinner and when Dan walked back from dinner, every time Dan made that trip. Either he spotted Dan before he was within earshot and instantly started playing the Godfather theme as some odd sort of joke or warning (Dan has yet to wake up with a bloody horse’s head at his feet), or he simply recognized the appeal to his audience of playing what may be the most familiar accordion piece. Our bet is that he did quite well. Had Bell performed on a Saturday afternoon, he likely would have attracted more listeners. Had he played shorter pieces on a subway platform rather than extended pieces next to the exit escalator, he might have attracted more listeners who had to wait for trains. And had he played the theme from The Godfather on his three-hundred-year-old violin, who knows.

Who Notices the Unexpected?

Chris once demonstrated the gorilla experiment to students in a seminar he was teaching. One of them told him the next week that she’d shown the video to her family, and that her parents had both missed the gorilla but her older sister had seen it. The sister then proceeded to crow about her triumph in this gorilla-noticing competition, claiming that it showed how smart she was. Dan regularly receives e-mails from people he’s never met asking why they missed the gorilla but their children saw it, or whether girls always notice but boys never do. A hedge fund manager found out about our study and had the people in her office do it. She tracked Chris down through a chain of acquaintances and interrogated him about the differences between people who notice the gorilla and people who don’t.

Many people who have experienced the gorilla experiment see it as a sort of intelligence or ability test. The effect is so striking—and the balance so even between the number who notice and the number who don’t—that people often assume that some important aspect of your personality determines whether or not you notice the gorilla. When Dan was working with Dateline NBC to create demonstrations, the show’s producers speculated that employees in detail-oriented occupations would be more likely to notice the gorilla, and they asked most of their “subjects” what their jobs were. They assumed that how you perform on the task depends on what kind of person you are: a “noticer” or a “misser.” This is the question of individual differences. If we could figure out whether some people consistently notice the gorilla and other unexpected events in laboratory tasks, then we could figure out whether they are immune to inattentional blindness more generally, and potentially train the missers to become noticers.

Despite the intuitive appeal of the gorilla video as a Rosetta stone for personality types, there is almost no evidence that individual differences in attention or other abilities affect inattentional blindness. In theory, people could differ in the total attentional resources they have available, and those with more resources (perhaps those with higher IQs) might have enough “left over” after allocating some to the primary task to be better at detecting unexpected objects. One argument against this possibility, though, is the consistency in the pattern of results we obtain with the gorilla demonstration. We conducted the original experiment on Harvard undergraduates—a fairly elite group—but the experiment works just as well at less prestigious institutions and with subjects who aren’t students. In all cases, about half of the subjects see the gorilla and half don’t. According to an online survey by Nokia, 60 percent of women and men think that women are better at multitasking. If you agree, you might also think that women would be more likely to notice the gorilla. Unfortunately, there is 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.

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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.

(#litres_trial_promo) 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.

(#litres_trial_promo) 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.

(#litres_trial_promo) 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.

(#litres_trial_promo) 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 tumor that was missed during the original reading might seem obvious in hindsight.

Unfortunately, people often confuse what is easily noticed when it is expected with what should be noticed when it is unexpected. Moreover, the procedures frequently used in hospitals when reviewing radiographs are affected by the illusion of attention; doctors themselves also assume that they will notice unexpected problems in an image, even when they are looking for something else. To reduce the effects of inattentional blindness, one can deliberately reexamine the same images with an eye toward the unexpected. When participants in our studies know that something unexpected might happen, they consistently see the gorilla—the unexpected has become the target of focused attention. Devoting attention to the unexpected is not a cure-all, however. We have limited attention resources, and devoting some attention to unexpected events means that we have less attention available for our primary task. It would be imprudent to ask radiologists to take time and resources away from detecting the expected problem in an x-ray (“Doctor, can you confirm that this patient has a pulmonary embolism so that we can begin treatment?”) to focus instead on things that are unlikely to be there (“Doctor, can you tell us whether we left anything behind in this patient’s body?”). A more effective strategy would be for a second radiologist, unfamiliar with the case and the tentative diagnosis, to examine the images and to look for secondary problems that might not have been noticed the first time through.