The Tipping Point: Chapter Five Summary & Analysis

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?

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.

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.

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.

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.

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.

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 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.