Free The Invisible Gorilla: And Other Ways Our Intuitions Deceive Us by Christopher Chabris, Daniel Simons

take special note of the fact that “sleep” was not on the list. Then, when you recalled the words, your mind
reconstructed
the list as best it could, based on both your specific memory for the words you saw and on your knowledge of how the words were generally related.
    When we perceive something, we extract the meaning from what we see (or hear, or smell …) rather than encode everything in perfect detail. It would be an uncharacteristic waste of energy and other resources for evolution to have designed a brain that took in every possible stimulus with equal fidelity when there is little for an organism to gain from such a strategy. Likewise, memory doesn’t store everything we perceive, but instead takes what we have seen or heard and associates it with what we already know. These associations help us to discern what is important and to recall details about what we’ve seen. They provide “retrieval cues” that make our memories more fluent. In most cases, such cues are helpful. But these associations can also lead us astray, precisely because they lead to an inflated sense of the precision of memory. We cannot easily distinguish between what we recall verbatim and what we construct based on associations and knowledge. The word-list example, originally devised in the 1950s by psychologist James Deese and then studied extensively by Henry Roediger and Kathleen McDermott in the 1990s, 5 is a simple way to demonstrate this principle, but memory distortions and the illusion of memory extend well beyond arbitrary lists of words.
    Just as the gorilla experiment showed that people see what they expect to see, people often remember what they expect to remember. They make sense of a scene, and that interpretation colors—or even determines—what they remember about it. In a dramatic demonstration of this principle, psychologists William Brewer and James Treyens conducted a clever experiment using a simple ruse. 6 Subjects in their study were led to a graduate student office and asked to wait there for a minute while the experimenter made sure the previous subject was finished. About thirty seconds later, the experimenter returned and led the subjects to another room, where they unexpectedlywere asked to write down a list of everything that they had seen in the waiting room. In most respects, the waiting room was a typical graduate student office, with a desk, chairs, shelves, and so on. Almost all of the subjects recalled such common objects. Thirty percent of them also recalled seeing books, and 10 percent recalled seeing a file cabinet. But this office was unusual—it contained no books or file cabinets.
    In the same way that people tended to recall having seen the word “sleep” when remembering a list of words associated with sleep, their memory reconstructed the contents of the room based both on what actually was there and on what
should have
been there. (If you look at a picture of the office, it will probably seem perfectly normal until someone points out what’s missing, and then it will suddenly start to look strange.) What is stored in memory is not an exact replica of reality, but a re-creation of it. We cannot play back our memories like a DVD—each time we recall a memory, we integrate whatever details we do remember with our expectations for what we should remember.

Memories in Conflict

    Neil Reed recalled Coach Knight choking him during a practice. He remembered Assistant Coach Dan Dakich having to pull Knight off him, but Dakich claimed it never happened. One of them had a distorted memory for the event, but which one? In most cases of disputed memory like this, there’s no definitive way to determine who was right and who was wrong. What makes this example particularly interesting is that well after Reed, Dakich, and others went public with their accusations and memories, a videotape of the practice surfaced. It showed Knight approach Reed, grab him by the front of the neck with one hand for