The Dunbar Number is the number of stable social relationships a person can maintain. Depending on the definitions and tests used, it ranges between about 100 and 250, with 150 being a rough rule of thumb. We can individually maintain only a certain number of relationships: We don’t have time to interact meaningfully with each of the many thousands of people we meet over the course of our lifetimes. Most days (or weeks), we have two-way conversations with only a few dozen at best - even if we have several hundred “friends” on various social media platforms.
Although often described as a fixed number, it is perhaps better understood as a smooth scale, with different social relationships having an ordering based on nearness: physical interaction, frequency and depth of social interaction, shared experiences, etc. The degree of interactions forms a hierarchy of social circles, with a few very close friends transitioning smoothly to a larger number of acquaintances and a huge number of people you’ve met once or barely know. Dunbar himself defined six thresholds ranging from 5 to 1500 individuals. Over time, individual acquaintances may move up or down this social gradient.
Our models of human interaction make sense from the point of view of discussing small, close-knit communities where you understand the behaviors and histories of every member, but struggles to keep up with the wide range of social interactions in a globally interconnected society.
All the above is fairly standard, but from this point I’ll get a bit more speculative: I think that the outer regions of your social graph, if not the inner ones, are directional relationships: Your understanding of someone and feelings of closeness to them are not necessarily reciprocal: Celebrities can have millions of followers who closely follow their personal lives, understand their tastes in music, food, and politics, and who would instantly recognize them by either face or voice. A substantial portion of what contributes to the closeness and quality of relationships encapsulated in Dunbar’s number is our ability to understand others’ motivations, to predict their reactions in different situations, and to empathize with their moods. Such understanding is not limited to bidirectional face-to-face relationships, although it is clearly easier to develop social knowledge & trust of another person when you’re interacting with them directly.
Furthermore, I think we leverage the same basic skills and mechanisms in trying to describe and predict people whom we can’t individually recognize or name: If gossip and reputation shape our understanding of individuals, it seems likely they do the same for groups of people. Although you can form individual relationships with a few hundred individuals, global population exceeds 7.5 billion. You interact with most of them in indirect ways: Some individual human ran the sewing machine that made your clothing, the printing press that made the cash in your wallet, and the construction crew that built your home. Your income is likely sourced from thousands or millions of consumers, funneled through salespeople, bureaucrats, and bankers you’ll never meet. The laws, police, and soldiers charged with maintaining order in your society report to government officials elected by millions of your compatriots with diverse political views. You depend on all those people, and occasionally seek to alter their behavior through voting, commerce, and your direct social interactions.
But you can’t possibly build detailed, individualized models so far in excess of your Dunbar number. Instead, you leverage stereotypes and other heuristics with varying degrees of fidelity. Almost always, no matter the group, the “in-group” is prized over the “out-group.” You have close, trusting relationships with people whom you regularly interact with, or with people who resemble them in face & manner. Other people are unknowns and therefore suspicious. The danger in this is not having the stereotypes, but in failing to recognize their limitations. If we want to accurately understand our political, economic, and social fault lines, we have to recognize our own minor cognitive abilities. Dunbar states we can’t form close relationships with everyone, but the nature of the relationships we do form is up to us, as are the fallback procedures we use for people outside our close social circles.
Remember the next time you’re interacting with a stranger who’s triggering your stereotypes that those stereotypes are giving you a simplified, cartoonish picture of them. It may be telling you something useful, but it may also be noise. If you want to function in society with them, you need to learn to deal with them. More accurate information is useful but hard to come by. Build your stereotypes with intention and monitor them for accuracy & utility. If a person you meet seems incomprehensible to you, chances are good you seem strange to them as well. Useful communication and persuasion will require you to bridge that gap.