CHAPTER 7
Sorting People and Things
Why we categorize things and stereotype people … what Lincoln, Gandhi, and Che Guevara had in common
We would be dazzled if we had to treat everything we saw, every visual input, as a separate element, and had to figure out the connections anew each time we opened our eyes.
IF YOU READ someone a list of ten or twenty items that could be bought at a supermarket, that person will remember only a few. If you recite the list repeatedly, the person’s recall will improve. But what really helps is if the items are mentioned within the categories they fall into—for example, vegetables, fruits, and cereals. Research suggests that we have neurons in our prefrontal cortex that respond to categories, and the list exercise illustrates the reason: categorization is a strategy our brains use to more efficiently process information.1 Remember Shereshevsky, the man with the flawless memory who had great trouble recognizing faces? In his memory, each person had many faces: faces as viewed from different angles, faces in varying lighting, faces for each emotion and for each nuance of emotional intensity. As a result, the encyclopedia of faces on the bookshelf of Shereshevsky’s brain was exceptionally thick and difficult to search, and the process of identifying a new face by matching it to one previously seen—which is the essence of what categorization is—was correspondingly cumbersome.
Every object and person we encounter in the world is unique, but we wouldn’t function very well if we perceived them that way. We don’t have the time or the mental bandwidth to observe and consider each detail of every item in our environment. Instead, we employ a few salient traits that we do observe to assign the object to a category, and then we base our assessment of the object on the category rather than the object itself. By maintaining a set of categories, we thus expedite our reactions. If we hadn’t evolved to operate that way, if our brains treated everything we encountered as an individual, we might be eaten by a bear while still deciding whether this particular furry creature is as dangerous as the one that ate Uncle Bob. Instead, once we see a couple bears eat our relatives, the whole species gets a bad reputation. Then, thanks to categorical thinking, when we spot a huge, shaggy animal with large, sharp incisors, we don’t hang around gathering more data; we act on our automatic hunch that it is dangerous and move away from it. Similarly, once we see a few chairs, we assume that if an object has four legs and a back, it was made to sit on; or if the driver in front of us is weaving erratically, we judge that it is best to keep our distance.
Thinking in terms of generic categories such as “bears,” “chairs,” and “erratic drivers” helps us to navigate our environment with great speed and efficiency; we understand an object’s gross significance first and worry about its individuality later. Categorization is one of the most important mental acts we perform, and we do it all the time. Even your ability to read this book depends on your ability to categorize: mastering reading requires grouping similar symbols, like b and d, in different letter categories, while recognizing that symbols as disparate as b, b, 
, and b all represent the same letter.
Classifying objects isn’t easy, 
. Mixed fonts aside, it is easy to underestimate the complexity of what is involved in categorization because we usually do it quickly and without conscious effort. When we think of food types, for example, we automatically consider an apple and a banana to be in the same category—fruit—though they appear quite different, but we consider an apple and a red billiard ball to be in different categories, even though they appear quite similar. An alley cat and a dachshund might both be brown and of roughly similar size and shape, while an Old English sheepdog is far different—large, white, and shaggy—but even a child knows that the alley cat is in the category feline and the dachshund and sheepdog are canines. To get an idea of just how sophisticated that categorization is, consider this: it was just a few years ago that computer scientists finally learned how to design a computer vision system that could accomplish the task of distinguishing cats from dogs.
As the above examples illustrate, one of the principal ways we categorize is by maximizing the importance of certain differences (the orientation of d versus b or the presence of whiskers) while minimizing the relevance of others (the curviness of versus b or the color of the animal). But the arrow of our reasoning can also point the other way. If we conclude that a certain set of objects belongs to one group and a second set of objects to another, we may then perceive those within the same group as more similar than they really are—and those in different groups as less similar than they really are. Merely placing objects in groups can affect our judgment of those objects. So while categorization is a natural and crucial shortcut, like our brain’s other survival-oriented tricks, it has its drawbacks.
One of the earliest experiments investigating the distortions caused by categorization was a simple study in which subjects were asked to estimate the lengths of a set of eight line segments. The longest of those lines was 5 percent longer than the next in the bunch, which, in turn, was 5 percent longer than the third longest, and so on. The researchers asked half their subjects to estimate the lengths of each of the lines, in centimeters. But before asking the other subjects to do the same, they artificially grouped the lines into two sets—the longer four lines were labeled “Group A,” the shorter four labeled “Group B.” The experimenters found that once the lines were thought of as belonging to a group, the subjects perceived them differently. They judged the lines within each group as being closer in length to one another than they really were, and the length difference between the two groups as being greater than it actually was.2