The Invisible Gorilla: And Other Ways Our Intuition Deceives Us. Christopher Chabris
the scene. As they talked about the party, the camera cut back and forth between them, sometimes showing a close-up of one of them, and other times showing both of them. After about a minute, the conversation ended and the screen faded to black.
Imagine being a subject in their experiment. You come to a laboratory room and are told that before you do another task, the experimenters would like you to watch a brief movie and then to answer some detailed questions about it. They advise you to pay close attention and they start the movie. As soon as the movie ends, they hand you a piece of paper that asks, “Did you notice any unusual differences from one shot to the next where objects, body positions, or clothing suddenly changed?” If you are like almost all of the subjects in this experiment, you would answer no—you would not have noticed any of the nine editing mistakes the two Dans intentionally made!15
These “errors,” which were of the same type that end up in books and websites on film flubs, included plates on the table changing color and a scarf disappearing and reappearing. They were much more obvious than the ones Josh Mankiewicz disparaged in his Dateline report. Yet even when subjects watched the film a second time, now looking for changes, they still noticed, on average, just two of the deliberate errors. This phenomenon, the surprising failure to notice seemingly obvious changes from one moment to the next, is now known as change blindness—people are “blind” to the changes between what was in view moments before and what is in view now.16 This phenomenon is related to the inattentional blindness we discussed in the last chapter, but it is not the same. Inattentional blindness usually happens when we fail to notice the appearance of something we weren’t expecting to see. The thing we miss, such as a gorilla, is fully visible, right in front of us the entire time. For change blindness, unless we remember that Julia Roberts was eating a croissant, the fact that she is now eating a pancake is unremarkable. Change blindness occurs when we fail to compare what’s there now with what was there before. Of course, in the real world, objects don’t abruptly change into other objects, so checking all the visual details from moment to moment to make sure they haven’t changed would be a spectacular waste of brainpower.
What is in some ways even more important than a failure to notice changes is the mistaken belief that we should notice them. Daniel Levin cheekily named this misbelief change blindness blindness, because people are blind to the extent of their own change blindness. In one experiment, Levin showed photographs from the Sabina/Andrea conversation to a group of undergraduates, described the film, and pointed out that the plates were red in one shot and white in another. That is, rather than run the change blindness experiment, he explained everything about it, including the intentional “flub.” He then asked these subjects to decide whether or not they would have noticed the change if they had just watched the film without being alerted to its presence. More than 70 percent confidently said that they would have spotted the change, even though in the original study no one actually did! For the disappearing scarf, more than 90 percent said they would have noticed, when again, in the original experiment, no one actually did.17 This is the illusion of memory at work: Most people firmly believe that they will notice unexpected changes, when in fact almost nobody does.
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.18
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.19 But when they don’t expect the change, they completely miss it.
Professional Change Detectors
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.20 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 2.21 “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