Read The Invisible Gorilla: And Other Ways Our Intuitions Deceive Us Online
Authors: Christopher Chabris,Daniel Simons
Now imagine you are in another experiment conducted by the two Dans. You come to the lab and again you are asked to watch a brief silent movie. You are warned that it is really short and that you should pay close attention. The movie shows a person sitting at a desk who gets up and
walks toward the camera. The shot then cuts to the hallway and shows a person exiting the door and answering a phone on the wall. He stands still, holding the phone to his ear and facing the camera for about five seconds before the scene fades to black. As soon as the movie ends, you are asked to write a detailed description of what you saw.
Having just read about the Sabina/Andrea film, you’ve probably guessed that there’s more to this one than just the simple action of answering a phone. When the camera cut from a view of the actor walking toward the doorway to a shot of the actor entering the hall and answering the phone, the original actor was replaced by a different person! Wouldn’t you notice the only actor in a scene being replaced by a different person wearing different clothes, parting his hair the opposite way, and wearing different glasses?
If you answered yes, you’re still under the illusion of memory. Here is what two subjects wrote after seeing the film:
Subject 1: A young man with slightly long blond hair and large glasses turned around from the chair at a desk, got up, walked past the camera to a phone in the hallway, spoke into the phone and listened and looked at the camera.
Subject 2: There was a blond guy with glasses sitting at a desk … not too cluttered but not exactly neat. He looked at the camera, rose, and walked out to the front right of the screen, his blue shirt billowing out a bit on his right over his white with light pattern tee-shirt … went into hallway, picked up phone, said something that didn’t seem to be “hello,” and then stood there looking kind of foolish for a bit.
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Not a single subject who viewed this video spontaneously reported anything different before and after the change. Even when prompted more specifically with the question, “Did you notice anything unusual about the video?” no subjects reported the change in the actor’s identity or even his clothes from the first shot to the second. In a separate experiment, subjects watched the same video, but with the person-change
pointed out to them. They were then asked whether they would have noticed the change had they viewed the video without the warning; 70 percent said they would have, compared with 0 percent who actually did. In this case, when people know about the change in advance, it becomes obvious and they all see it.
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But when they don’t expect the change, they completely miss it.
In most cases, we have almost no feedback about the limits on our ability to spot changes. We are aware only of the changes we do detect, and, by definition, changes we don’t notice cannot modify our beliefs about our change-detection acumen. One group, though, has extensive experience looking for changes to scenes: script supervisors, the professionals responsible for detecting continuity errors when making movies.
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Are they immune to change blindness? If not, do they at least have above-average awareness of the limits on their ability to retain and compare visual information from one moment to the next?
Trudy Ramirez has been a Hollywood script supervisor for nearly thirty years. She got her start working on commercials and quickly moved up to feature films. She has been the script supervisor on dozens of major movies and television programs, including
Total Recall, Basic Instinct, Terminator 2
, and
Spider-Man 3
. Dan spoke with Trudy Ramirez while she was working on the set of
Iron Man 2.
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“I have a very good visual memory, but I also take copious notes,” she said. “I know that writing something down that I want to remember will often cement it into my memory.” The key, according to Ramirez, is that script supervisors realize they don’t need to remember everything. They focus on those details and aspects of a scene that matter, and ignore the rest.
“Most of the time, I will remember what is important to the scene,” she continued. “We know what to look for. We know how to look.” Everyone on a film set has their own area of focus when watching a scene, but script supervisors are trained to look for those aspects of the
scene that are central to facilitating the editing of the film. Ramirez noted, “There are points in the action of a scene where you know the editor will most likely cut: when someone sits or stands up, when someone turns around, or when someone comes into or goes out of a room…. You start to develop a sense of how things will cut together, and therefore what is important to notice.” Script supervisors also learn what is important from experience, often painfully: “Over time, we all make tragic continuity errors which train us what to look for—whatever you didn’t notice that you later wished you had trains you to notice that thing or action next time.”
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So script supervisors are not immune to change blindness. The difference between them and everyone else is that script supervisors get direct feedback that they can and do miss changes. Through their experience of searching for errors and learning about their mistakes, they become less prone to the illusion that they can notice and retain everything around them. Ramirez said, “The one thing this has taught me is that my memory is very fallible. It’s shockingly fallible. You wouldn’t necessarily have any reason to think about how your memory was working unless you were doing something such as script supervising where it’s such an important part of it.” Critically, though, she knows that other people have similar limits. “When I am watching a movie, the more into the story I am, the less I notice things that are out of continuity. If I’m being swept along by the story and I’m involved with the characters, I am much less apt to notice something out of visual continuity. If you’re really into the story, huge continuity errors will go right by you—you’re not looking for those kinds of details…. You can get away with a lot.”
What does that say about people who make a habit of searching for continuity errors? If people spot continuity errors when watching a film, then the movie may have a bigger problem: It doesn’t engage viewers’ attention enough to keep them from searching for minor changes! Of course, some people will watch a movie multiple times just to look for errors. And if they do that, they are likely to find some. The impossibility of noticing everything is what guarantees the business prospects for books and websites on film flubs.
Professor Ulric Neisser, whose research inspired our gorilla experiment, watched the change blindness demonstration in which an actor changed into another person while answering a phone, and he pointed out a possible limitation of all of these studies: They all used videos. He commented that watching video is an inherently passive activity: The action unfolds in front of us, but we do not actively engage with it the way we do when we interact socially with other people. Neisser argued that change blindness might not occur if a person were changed in the middle of a real-world encounter rather than across a cut in a passively viewed motion picture. The two Dans thought Neisser probably was right, that people would notice such a change in the real world, but they decided to run an experiment to test Neisser’s prediction anyway.
Imagine you are strolling across a college campus and up ahead of you, you see a man holding a map and looking lost. The man approaches you and asks directions to the library. You start giving him directions, and as you’re pointing to the map, a couple of people behind you abruptly say “Excuse me, coming through,” and they rudely carry a big wooden door right between you and the lost pedestrian. Once they pass, you finish giving directions. Would you notice if the original lost pedestrian were replaced by a different person as the workers carried the door through? What if the two people wore different clothes, differed in height by about three inches, had different builds, and had noticeably different voices? You would have to be pretty oblivious to miss the change. After all, you were in the middle of a conversation with the man, and you had plenty of time to look at him. That’s certainly what the two Dans and Ulric Neisser thought.
That’s also what more than 95 percent of undergraduates thought when asked whether they would notice.
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And they were all wrong. All of us, undergraduates as well as scientists familiar with all of the research leading up to these experiments, fell prey to the illusion of memory. All were convinced that only the rare, unusually oblivious person could possibly miss the change. Yet nearly 50 percent of the people in
the original experiment did not notice that they were talking to different people before and after the interruption!
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Serendipitously, one day several years later when we were conducting a followup experiment at Harvard, many of the undergraduate psychology students were attending a lecture in the basement of the building. During the lecture, Professor Stephen Kosslyn (Chris’s graduate school mentor and longtime collaborator) happened to describe the “door” study in detail as an example of research being conducted by other faculty members in the department. When they left the lecture, several students were overheard making comments like, “There’s no way I would have missed that change.” Our recruiter asked them if they would like to be in an experiment and sent them to the eighth floor. As they stood at a counter after filling out a form, the experimenter who had been talking to them ducked down behind the counter—ostensibly to file away some papers—and a different person stood up. All of the students missed the change!
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Change blindness is a surprisingly pervasive phenomenon considering that it has only been studied intensely since the 1990s. It occurs for simple shapes on a computer display, for photographs of scenes, and for people in the middle of a real-world interaction.
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And the illusion of memory leads people to believe that they’re great at change detection even though they’re lousy. This illusion is so powerful that even change blindness researchers regularly experience it. We only came to recognize the limits of our intuitions about memories when our own data repeatedly showed us how wrong we could be. Similarly, filmmakers learn about the illusion of memory the hard way, by seeing evidence of their own mistakes on the big screen. Trudy Ramirez, the Hollywood script supervisor, has experienced this many times: “The way you remember something, how your memory shapes what you think you saw, as sure as you think you are … often it’s different if you can actually look back at it. There were times when I would have staked my life on something and later on realized I was wrong.”
There are limits to change blindness, of course. When we spoke publicly about the early person-change studies, we were often asked whether people would notice if a man changed into a woman. “Of course they
would,” we thought, but of course our certainty was another reflection of the illusion of memory. The only way to find out was to try it. Later experiments in Dan’s lab showed that people do in fact notice when you change a man into a woman or when you change the race of an actor in a movie. And people are more likely to notice a change to the identity of a person who is a member of their own social group.
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But most other changes often go undetected.
Even when subjects notice the person swap in these real-world experiments, they’re far from perfect in picking the original experimenter from a photographic lineup. And people who miss the change do no better with the lineup than they would have done by just guessing randomly.
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In a brief encounter, we appear to store so little information about another person that we not only fail to see changes, but we also can’t even identify the person we saw just minutes earlier. When you interact briefly with a stranger, there are only a few pieces of general information you can be certain of retaining: sex, race, and social group (student, blue-collar worker, businessperson, and so on). Most of the rest of what you perceive about the person probably won’t make it into memory at all.
Recall Leslie Meltzer and Tyce Palmaffy, who witnessed a knife attack from their car but recalled it differently just moments later. In light of the evidence that people sometimes fail to notice that a person has almost instantaneously been replaced by someone completely different, Leslie and Tyce’s discrepant eyewitness memories are unsurprising. After all, they were just observing the person from a distance, not standing face-to-face with him and giving him directions.
About ten years ago at a party Dan hosted, a colleague of ours named Ken Norman told us a funny story about sitting next to the actor Patrick Stewart (best known for his roles as Captain Jean-Luc Picard of
Star Trek
and Charles Xavier in the
X-Men
films) at a Legal Sea Food restaurant in Cambridge, Massachusetts. The story was prompted when Chris noticed that Dan had a small figurine of Captain Picard
perched next to his television screen. “Can I buy your Captain Picard?” asked Chris. Dan said that it was not for sale. Chris offered five, then ten dollars. Dan refused. Chris eventually raised his bid to fifty dollars—for reasons that escape him now—but Dan still refused. (Neither of us remembers why Dan refused, but to this day, Picard has not left his place amid Dan’s electronics.)
At this point Ken told us that at Legal Sea Food, Patrick Stewart had been dining with an attractive younger woman who, based on snippets of overheard conversation, appeared to be a publicist or agent. For dessert Stewart ordered Baked Alaska—a choice that stood out in memory because it appears rarely on restaurant menus. Toward the end of his meal, another distinctive event happened: Two members of the kitchen staff came out to Stewart’s table and asked for his autograph, which he readily granted. Moments later, a manager appeared and apologized, explaining that the “Trekkie” cooks’ action was against restaurant policy. Stewart shrugged off the supposed offense, and he and his companion were soon on their way.