In 1996, a writer and actress named Rebecca Wells published a book, Divine Secrets of the Ya-Ya Sisterhood. The book sold modestly at first. But slowly, the book developed a cult following, until eventually, it became one of the best-selling books of the 1990s. Why did this book eventually become so popular?
Wells’s literary career fits the same format as the earlier anecdotes about Hush Puppies or syphilis: a sudden, unexpected upshot in popularity and pervasiveness of the “infectious agent,” in this case Wells’s book.
The size of a group plays a huge role in social epidemics. For example, a comedy playing in a large movie theater will often get more laughs (both overall, and per person) than the same film playing in someone’s home—the “peer pressure” of other people laughing inspires extra laughter, as if laughter is contagious. Rebecca Wells’s book became a hit in part because she toured through San Francisco, where book club groups were especially popular. In book clubs, certain readers bonded over Wells’s book, and wanted to share their experience with other people—so they bought more copies of the book. Love for the book was contagious in the same way that laughter can be contagious in a large movie theater. So groups can be hugely important in starting social epidemics: when a group likes a product or idea, the members of the group will often spread the product or idea to other people.
Wells’s success as an author isn’t only the result of her literary talent; her book’s success was also a product of numerous book clubs’ enthusiasm. The people in book clubs were likely to enjoy Wells’s book, it’s suggested, because they were surrounded by other people who enjoyed it. In the previous chapter, Gladwell showed how small details of an environment, such as the amount of graffiti on the walls, can influence a person’s behavior. In this chapter, Gladwell will show that other people, particularly groups of people, can similarly influence behavior in subtle, unexpected ways.
Numerous studies of human cognition have come to parallel conclusions: the human brain can divide random stimuli into about six or seven different categories. For example, the average person can distinguish between about six different musical notes before getting confused. Similarly, most phone numbers are seven digits, since the average person can remember about seven digits before starting to forget them all.
The human brain’s propensity for remembering combinations of six or seven is a good example of how the mind can be “hard-wired” to think in terms of specific numbers.
Much as the numbers six and seven represent a limit on how many stimuli the human brain can keep separate on average, the number 150 represents a limit on how many social relationships the brain can usually keep straight. Evolutionary psychologists have noticed that the size of different primates’ brains correlates closely with the average group size for that species. Species of primate that cluster in larger groups almost always have the largest cortexes and the greatest cerebral power. Psychologists have even extrapolated from the data to suggest that 150 is, on average, “the maximum number of individuals with whom we can have a genuinely social relationship.” The number 150 pops up frequently in anthropology and history. In many different societies across the world, the average village size is about 150, and historically, generals have organized their fighting forces into units of about 150-200. Various religious congregations have also organized into groups of 150.
While the evidence is incomplete, evolutionary psychologists (i.e., people who study the ways the mind has changed over millennia in response to natural selection) theorize that the mind changes with respect to increasing group size. Thus, the average community size of a proto-human species correlates closely with brainpower. The same is true of human beings: specifically, the number 150 seems to be an upper limit on the size of a close-knit, communicative group.
Gladwell proposes a “Rule of 150”—a group with 150 members or less is often able to organize itself, make decisions, and avoid serious arguments, while a group with more than 150 members is often unable to do the same. Moving from 140 members to 170 members might seem like a small change, but in fact the change can have huge consequences.
Gladwell isn’t saying that the number 150 is an absolute—there may be groups of 160 that function better than other groups of 140. Nevertheless, 150 is a useful benchmark, rather than a hard limit, for analyzing successful and unsuccessful groups.
Consider Gore Associates, a billion-dollar tech firm. Gore is an unusual company because it has no job titles. Employees have no specific bosses, and salaries are determined collectively. All employee offices are the same size. In short, Gore is organized like a small company, despite the fact that it’s worth a billion dollars and has hundreds of employees. Wilbert Gore, the founder of the company, explains that he was able to keep the company “small-feeling” by using the rule of 150: he ensured that no branch of the company would have more than 150 employees.
Gore uses sociological techniques to maximize its productivity: by capping the number of employees per branch at 150, Gore ensures that its employees are more likely to trust one another, cooperate well, and generally perform successfully as a business community.
Other associates of Gore explain that “peer pressure” plays a vital role in the company’s success. Gore employees claim that when an employee is surrounded by a small number of peers and coworkers who all know him well, the employee will be more incentivized to succeed than he would be if working under a boss.
One reason that the rule of 150 is so useful is that groups of 150 or fewer people will be more likely to know one another closely—they’ll personally be acquainted with everyone at the company, arguably increasing productivity.
One advantage to working at a company like Gore is that the “transactive memory” of the employees is much larger than it would be at a regular company. Transactive memory is a form of memory in which two or more people are responsible for remembering a set of information. When the two or more people involved in this endeavor know one another well, they’ll organize themselves intuitively, so that certain people remember certain pieces of information. Transactive memory is highly efficient. Most close families have a very high transactive memory—different family members remember specific aspects of the family’s experience; furthermore, certain family members might specialize in remembering certain kinds of information. The 150 employees at any given Gore branch have an enormous transactive memory, because they’ve organized themselves to remember different parts of the business.
Another major advantage of the rule of 150 is that groups of 150 people or fewer naturally divide up into different tasks or business sectors: for example, some people will naturally specialize in customer service, production, etc. In most ordinary companies, employees specialize based on their job descriptions: an employee focuses on his sector of the business because that’s his job. Gladwell suggests that Gore’s self-organization is more efficient because there will be fewer redundancies: at an ordinary company, people’s responsibilities might overlap, whereas at Gore, 150 people cover every aspect of the business comprehensively and efficiently.