No Matter What Twitter Says, You've Got No More Than 150 Friends

People keep talking about how social media changes our brains. Sure it does: The human brain is a plastic, dynamic organ and is changing at every moment, so surely something like Twitter that assaults your brain for hours a week will change it in some way — creating new memories, inciting feelings, reinforcing habits, and delivering lots of sensory input. The more interesting question concerns how fundamental those changes are, or have the potential to be. Is social media changing humans’ basic social psychology?

The most common examples of this purported change relate to how social media promotes a general superficiality by spreading thin our connections, causing us to focus on the relationship of our online avatar to its hundreds or thousands of "friends" and "followers" rather than the handful of stable, invested relationships we had pre-21st century life. One of the central lines of this argument is that having, say, a thousand friends on Facebook or ten thousand followers on Twitter suggests a social life that values quantity over quality.

This line of thought has always reeked of bullshit to me. To argue that a media interface has the power to seriously alter or reverse hundreds of thousands of years of human-specific psychological evolution is a heavy claim and bears the burden of proof.

There's a golden number in biological anthropology, akin to the magic 7 plus or minus 2 of psychology, that refers to the average maximum amount of "stable" social relationships a given human can realistically maintain. The British anthropologist Robin Dunbar popularized this idea, and the number has since been called "Dunbar's Number."

Let me unpack this a bit: In human evolutionary history, the amount of other humans one meets in her life has obviously increased drastically. Surely, the few hundred humans Scrum the Cave Person met over his life circa 240,000 BC pales in comparison to the thousands of humans Willelmus the Medieval Welsh Blacksmith met circa the 1360s, and both are dwarfed by the tens of thousands of humans you've met. But just “meeting” someone is a vague experience. Think of how many lame people you meet — at shitty bars, embarrassing theme parties, emergency room bathrooms, or wherever gross places you tend to meet strangers — whose stupid job you keenly regret asking about. Now think about your stable relationships, the people you actively seek out, work with, have sex with, or are, sometimes regrettably, related to. Thinking of these people has a sort of extra mental "weight" to it, as if they're physically taking up more space in your personal little brain box.

Well, they are. Dunbar's number, which is approximately 150 people, refers to the maximum amount of stable, important relationships the human neocortex — the evolutionarily recent brain region that has been shown to have a central role in the maintenance of social relationshsip — can efficiently keep track of. Keeping up stable, complex relationships takes a lot of mental space. If you think remembering names and faces is hard enough, throw in the life histories, mood eccentricities, unique personalities, desires, values, and conversational style that are requisite to truly knowing someone. Multiply that by 150 and you can see why hermits are enviable. There's even a popular theory, championed by Dunbar himself, that the exceptional relative size of the human brain evolved in order for our particularly social species to navigate the thicket of connections and details present in every complex social relationship.

Dunbar has applied his number to the amount of people companies tend to have working in one building, the average sizes of army units since the Roman empire, hunter-gatherer tribes of past and present, and now, new lines of research are finding the magic number in online social networks.

That may seem weird, as 150 is a small number of Facebook friends – the kind of number reserved for grandmas, loners, and your cousin's horrendous metal band. But a research group led by Bruno Goncalves at the University of Indiana, has recently published a paper (which is open-source and available for free) arguing that the magic number is indeed laying unnoticed under the millions of connections present in social media. The authors studied Twitter, modeling the tweets and private messages of over 1.7 million users. They weighted the strength of connections between users by valuing the frequency of reply tweets and messages between them, defining stable relationships (to use Dunbar's phrase) as those that fit their specific function of reciprocity. When they crunched the numbers, they found that the number of stable relationships users had peaked around 80, and sharply dropped after about 150, supporting the idea that Dunbar's number is a ceiling. They wrote:

Online [social] tools might be analogous to a pocket calculator that, while speeding up the way we can do simple math, does not improve our cognitive capabilities for mathematics. In this case, the basic cognitive limits to social interactions are not surpassed in the digital world.

The case could be made that if you have 150 truly "stable" friends on Facebook or Twitter, you may have a somewhat different set of 150 friends in the real world, thus increasing the overall number to a value over 150. This makes sense, though there would certainly be tons of overlap of serious friends you see in person and talk to via social media. But remember, 150 is the max, not the average. However, it may be the case that social media is pushing us towards operating closer to our 150 maximum because it gives us the ability to maintain a huge magnitude of relationships that would have otherwise disintegrated.

Further research on the subject will be interesting. It could be possible that thousands of years from now, online social media will have played a role in increasing Dunbar's number (assuming the internet doesn’t fall completely prey to ignorant politicians and business interests), which would be a concrete case of the internet directly affecting the evolution of fundamental human psychology. It's too early to tell now if any such effect will occur.

Here’s the take home lesson: The next time you think of someone you want to seriously reconnect with, Facebook message them, and, if they respond, consider squeezing them into your sacred 150 so you can finally kick out that high school friend with halitosis. Not that you'd never think to unfriend him, of course.