Your Brain Can Only Handle a Few Close Friends

If all the world's a stage, and all the men and women merely players, everyone you talk to has a certain role. It turns out, however, that the actors are interchangeable.

Previous studies have suggested that, despite what some social climbers may think, and despite Facebook friend numbers that can climb well into the thousands, it's pretty much impossible to have an IRL social network of more than about 150 people. That’s been called “Dunbar’s number,” named after the anthropologist, Robin Dunbar, who first proposed it. It can vary from person to person, but it turns out that even among smaller circles, there’s a seemingly strict limit to how much attention one person can dole out.

A new study published in Proceedings of the National Academy of Sciences suggests that humans have, almost uniformly, a “one-in-one-out” policy—every time you become close to a new person, someone else subconsciously gets the boot.

“Although social communication is now easier than ever, it seems that our capacity for maintaining emotionally close relationships is finite,” said Felix Reed-Tsochas, a researcher at Oxford University and an author of the study. “While the number varies from person to person, what holds true in all cases is that at any point individuals are able to keep up close relationships with only a small number of people, so that new friendships come at the expense of ‘relegating’ existing friends.”

To test the finding, the researchers followed 24 British students as they left school and entered the workforce or a university. Researchers used both survey results from the participants and automatically-logged cell phone data to track who their “closest” friends were.

As you might guess (you are a human, presumably one with at least a few friends, after all), the majority of calls and energy was spent on a very small number of close friends and family. When these calls were graphed, a few people made up a large fraction of them, followed by a long, declining tail of others.

Most surprisingly, however, was the fact that it didn’t matter which friends were deemed closest or which friends someone ultimately lost touch with: The shape of the graphs remained essentially the same.

What that means, in other words, is when you meet a new best friend, they’re likely to slide into your old bestie’s spot in your social circle—you’re unlikely to keep your level of communication the same with your old friend. According to the authors, the “social signature,” or graph of an individual person “remains stable and retains its characteristic shape over time and is only weakly affected by network turnover.”

“Thus, individuals appear to differ in how they allocate their available time to [friends], irrespective of who these [friends] are,” they continue. And don’t say that you keep in touch through GChat or Facebook or face-to-face communication: The student surveys show that “this finding applies not just to call frequencies, because the frequency of calls to a [friend] correlates with emotional closeness and frequency of face-to-face interactions.”

So next time your old friend asks what happened between you guys, you might have a real reason to say it’s you, not them. Or you can tell them that you can’t keep growing as a person with them still in the mix. The researchers found these constraints regardless of who they were studying.

“Because of these constraints, individuals cannot increase the number of [friends] they communicate with at maximum rate, but must downgrade (or drop) some individuals if they wish to add new ones to their preferred network at a high level of emotional intensity,” they wrote.

Tell them it’s nothing personal, you just need to make sure the “overall shape” of your “social signature” is preserved. They’ll probably feel the same.