In A Nutshell
According to professor and anthropologist Robin Dunbar, the most friendships we can actively maintain is 150. That’s because our brains have been hard-wired throughout human history to exist in social groups of no more than 150 since the time we were hunter-gatherers. Relationships take work, maintenance, and brainpower, and 150 quality friends is the most we’re able to manage.
The Whole Bushel
Go on, have a look at how many friends you have on Facebook. (We’ll wait.) How many? Maybe a few hundred?
If you have 100 or so friends, chances are you actually know the people on your friends list, communicate with them in some form, and know a little something about them. Once you get into the 250+ range, your connections with them get a little iffy and, let’s face it, you probably don’t know why half of them are there.
That’s because of Dunbar’s number. The social and evolutionary theory developed by Oxford University anthropology professor Robin Dunbar states that the largest number of interpersonal relationships we’re able to maintain at one time is 150. He also says that as each person’s friend count (or claimed friend count) goes up, the quality of those friendships goes down, suggesting that quality really is counterbalanced with quantity.
It all has to do with how our brains are wired and generations and generations of social and evolutionary history.
Humans can recognize about 1,500 faces, but recognizing who someone is and being able to remember their name doesn’t make it a friendship. The more people you add to your social circle, the more time, energy, and brainpower you spend just trying to remember names and important details like where you saw them last—and the less you have to devote to remembering the more intimate details, like the name of their beloved childhood pet or what subject they hated in school.
Dunbar’s research has shown that there’s an interesting correlation between the size of our brains, the size of our social groups, and the quality of the relationships we tend to form. Species that are generally monogamous (whether they’re humans, birds, or other animals) tend to have larger brains than non-monogamous species. Dunbar suggests that’s to allow them to process the enormous amount of information that’s necessary to keep filed away and readily available in the maintenance of a single strong relationship. Relationships—and even friendships—are hard work, and we need that processing power.
That processing power only goes so far, though. Historically, there are a wide range of examples of social groups that have naturally capped themselves at 150. Many hunter-gatherer groups have been shown to live in widespread groups of about 150. Medieval villages typically maxed out at 150 residents, and right up through modern times, it’s the number of soldiers in many military groups that are designed to be able to work closely together. Even in the animal world, those animals that live in social groups are typically found in family units of no more than 150.
Studies of modern corporations have also found that once the number of employees rises much beyond that magic number, you’re less likely to have coworkers and colleagues that are also friends outside of work, you’re less likely to be able to greet people by name, and you’re more likely to feel invisible and overwhelmed by the social network of the workplace.
Still doubting? Take another look at your friends on Facebook, and count how many of them you could not only ask for a serious favor, but those who you know would do it. Those are the types of relationships that are capped, because it takes two to maintain the friendship and keep communication open. Today, with not only the advent of technology but our tendency to wander far from the home we were born into, the formula still holds up. Dunbar suggests that the number may rise someday, but before that can happen, we need to grow bigger brains.