Passage II

SOCIAL SCIENCE: This passage is adapted from The Tipping Point: How Little Things Can Make a Big Difference by Malcolm Gladwell (©2002 by Malcolm Gladwell)

There is a concept in cognitive psychology called the channel capacity, which refers to the amount of space in our brain for certain kinds of information. Suppose, for example, that I played you a number of different musical tones, at random, and asked you to identify each one with a number. If I played you a really low tone, you would call it one, and if I played you a medium tone you would call it two, and a high tone you would call three. The purpose of the test is to find out how long you can continue to distinguish among different tones. Most people can divide tones into only about six different categories before they begin to make mistakes and start lumping different tones in the same category. This is a remarkably consistent finding. If, for example, I played you five very high pitched tones, you’d be able to tell them apart. And if i played you five very low pitched tones, you' d be able to tell them apart. You’d think, then, that if I combined those high and low tones and played them for you all at once, you’d be able to divide them into ten categories. But you won’t be able to. Chances are you’ll still be stuck at about six categories.

As human beings, we can only handle so much information at once. Once we pass a certain boundary, we become overwhelmed. What I'm describing here is an intellectual capacity—our ability to process raw information. But if you think about it, we clearly have a channel capacity for feelings as well.

Take a minute, for example to make a, list of all the people whom you would consider yourself truly close to. The average answer is 12 names. Those names make up what psychologists call our sympathy group. Why aren’t groups any larger? Partly It's a question of time. If you look at the names on your sympathy list, they are probably the people whom you devote the most attention to. If your list was twice as long, would you still be as close to everyone? Probably not. To be someone’s friend requires a minimum investment of time. More than that, though, it takes emotional energy. At a certain point, at somewhere between 10 and 15 people, we begin to overload, just as we begin to overload when we have to distinguish between too many tones.

Perhaps the most interesting natural limit, however, is what might be called our social channel capacity. The case for a social capacity has been made, most persuasively, by the British anthropologist Robin Dunbar. Dunbar begins with a simple observation. Primates—monkeys, chimps, baboons, humans—have the biggest brains of all mammals. More important, a specific part of the brain of humans and other primates— the region known as the neocortex, which deals with complex thought and reasoning—is, huge by mammal standards. For years, scientists have argued back and forth about why this is the case. One theory is that our brains evolved because our primate ancestors began to engage in more sophisticated food gathering: instead of just eating grasses and leaves they began eating fruit, which takes more thinking power. You travel much farther to find fruit than leaves, so you need to be able to create mental maps. You have to worry about ripeness. You have to peel parts away in order to eat the flesh of a fruit, and so on. The problem with that theory is that if you try to match up brain size with eating, patterns among primates, it doesn’t work. So what does correlate with brain size? The answer, Dunbar argues, is group size. If you look at any species of primate—at every variety of monkey and ape—the larger their neocortex is, the larger the average size of the groups they live with.

Dunbar’s argument is that brains evolve, they get bigger, in order to handle the complexities of larger social groups. If you belong to a group of five people, Dunbar points out, you have to keep track of ten separate relationships: your relationships with the four others in your circle and the six other two-way relationships between the others. That’s what it means to know everyone in the circle. You have to understand the personal dynamics of the group. If you belong to a group of twenty people, however, there are now 190 two-way relationships to keep track of: 19 involving yourself and 171 involving the rest of the group. Even, a relatively small increase in the size of a group creates a significant additional social and intellectual burden. Humans socialize in the: largest groups of all primates because we are the only animals with brains large enough to handle the complexities of that social arrangement.