Your Brain Can Only Handle a Limited Number of Close Friends

"Let’s say I’m the kind of guy who has four really close friends at the beginning of the study," social scientist Felix Reed-Tsochas says. "I will still have four close friends at the end of the study, but not necessarily the same four close friends."

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To Felix Reed-Tsochas, your social circle is less a circle than an onion.

"You can imagine the different layers," he says by Skype from Oxford, where he's a lecturer in complex systems (with a background in theoretical condensed matter physics) at the University of Oxford's Saïd Business School. "From my perspective, there's a bunch of really close friends – these are the people who will drop everything, and rush to me if I'm in an emergency. That's the inner layer of the onion. The next layer is the really close friends, but they're not quite in that category. Then maybe there are looser friends."

Those people are, you know, a couple layers farther out, followed by the friends-you-haven't-seen-since-college, the people-you-sort-of-know-at-the-coffee-shop, the friends-of-friends-who-are-more-like-acquaintances. Most of us have probably vaguely conceived of our social network in some set of concentric rings like this (you have definitely done this if you've ever planned a wedding).

Reed-Tsochas and his colleagues, though, have recently made some fascinating discoveries about exactly how this onion works (and, well, because cities are fundamentally composed of networks of social ties, we got sucked in by his story). In a study just published in the Proceedings of the National Academy of Sciences, Reed-Tsochas and a group of researchers from the University of Chester in the U.K., and the University of Aalto, in Finland, studied the social lives of 24 young adults on the cusp of finishing high school and either entering the work force or college.

These people were, in other words, in social transition, with new relationships forming and others receding to the background. The researchers gave them a series of more traditional surveys about who was in their social network and how they ranked their closest ties. They were then each given a pre-paid cell phone for the next 18 months, allowing the academics to observe exactly who they talked to – or, rather, how they allocated their limited social communication.

The study confirmed a pattern that previous research has detected: Amid the total universe of all the people we know, we generally each have a very small inner circle. If you were to rank-order the people we talk to the most, the majority of our attention would be devoted to just a handful of friends or family – those at the center of the onion. The patterns looks something like this, with our social network (and the number of calls to each person) at left and the ranking of its members at right:

"Persistence of Social Signatures in Human Communication," by J. Saramaki et al in PNAS.

Extend that picture out, and our social network looks on a graph like it has a steep curve at first (maybe with "steps" down between onion layers) and then a very long tail. Here are two subjects from the study, shown in three six-month intervals:

J. Saramaki et al

What's remarkable is not just that this pattern is broadly consistent across all of the people in this study. But, with some individual variation, it was consistent over the length of the study, too, even as subjects made new friends or parted ways with old ones.

"One of the really interesting things we found – and we can do this because we’re now watching what happens over time – is the signature of how many people are in each layer remains the same over time," Reed-Tsochas says. The authors use the term "social signature" to describe these patterns because mine is slightly different from yours, even if they all subscribe to a similar structure. I might have three people in my inner onion while you have five. But that number doesn't change over time for me.

"So what does that mean?" Reed-Tsochas says. "Typically, let’s say I’m the kind of guy who has four really close friends at the beginning of the study. I will still have four close friends at the end of the study, but these are not necessarily the same four close friends."

And if the shape of your social network is relatively fixed, you probably cannot transform yourself from being the kind of person who relies on only two confidants to the guy who has eight best men at his wedding. This idea in particular could have implications for sociologists and policymakers who would like to figure out how to increase social capital for isolated people who have little of it.

All of this also means that our social networks are likely constrained in some fundamental ways: by the time we have to spend with people, by the emotional capital we have to give them, maybe even by our cognitive capacity to bring more relationships on board.

"Perhaps there’s something hardwired into our brain as a consequence of evolution that to a certain extent determines how we are able to structure our social world," Reed-Tsochas says.

And if that's the case, then advances in communication technology that were supposed to be revolutionizing our social networks probably aren't doing that after all. The ease of communication enabled by cell phones doesn't necessarily allow you to grow closer to more people. And that guy you know who has 1,000 friends on Facebook?

"It isn't exactly that the computer has just done some amazing transformation of what humans are capable of doing socially, and that person now genuinely has 1,000 bosom-buddy friends," says Reed-Tsochas. Most of those people are from the outer layers of the onion. Facebook (or Twitter or email) has certainly made it easier to stay in touch with these far-flung acquaintances, but it hasn't fundamentally changed the number or depth of your relationships with the people closest to you.

Modern communication tools were also supposedly going to eliminate the importance of "distance" in our lives, and we've repeatedly seen evidence that this isn't true. This same technology is changing our world and how we interact with each other in many ways, but perhaps not quite so fundamentally as to alter our inherent "social signatures."

Top image: Christian Mueller/

This article is from the archive of our partner The Wire.