R.I.M. Dunbar :

You've probably heard of Dunbar's number before—he's the evolutionary psychologist who hypothesized that ~150 people is the "cognitive limit to the number of individuals with whom any one person can maintain stable relationships"

Dunbar's number is a perennial pop psychology headline (You Can Only Have 150 Friends!?! ), but in my experience, most people view it to be a pretty plausible theory for social relations

This phenomenon is an emergent property—or an intentional organizational principle—of many kinds of social coordination systems

(e.g. villages, academia, military, corporations)

What most people don't know is that Dunbar's number describes only one of the concentric circles of relations surrounding an individual

They scale by roughly a factor of 3, and "frequency of contact, emotional closeness, and altruism all decline across successive circles"

There a lot of ways to define and circumscribe each layer of relationships, but Dunbar roughly describes them as:

- primary partner (1.5)
- intimate friends (5)
- best friends (15)
- good friends (50)
- 'just' friends (150)
- acquaintances (500)
- names/faces (1500)

According to Dunbar, most people spend the majority of their social time and energy inside their first three layers

This has a lot to do with time scarcity and frequency requirements

Most of us contact our primary partners daily, but Dunbar proposes that you need to interact with a friend at least weekly to qualify for the 5-layer, monthly for the 15-layer, and annually for the 150-layer

"If someone is contacted less often than the defining rate for more than a few months, emotional closeness will inexorably decline to a level appropriate for the new contact rate"

This is why moving, graduate college, etc. suck so much—your entire graph recedes outward

Romantic relationships also tend to crowd out other Dunbar slots, if only temporarily. Ever had a friend fall in love, then drop off the face of the earth?

It's an interesting exercise to try mapping your own social graph onto Dunbar's bullseye configuration—do the circles seem accurate to you?

What about interaction frequency v. closeness? How often do you contact your 5-layer friends? 15-layer? 150-layer?

And what about exceptional cases?

Do you know someone who might be an outlier here?

Someone whose circles are noticeably tighter/broader than the numbers laid out on Dunbar's bullseye? How do these people's habits deviate from the norm?

Several examples come to mind...

Dunbar has done similar research with other apes, including chimpanzees, gorillas, and orangutans, among others

Interestingly, Dunbar's number for chimpanzees is around 50—a group size at which most observed chimpanzee tribes begin to fracture

Apes maintain group cohesion through 'social grooming', where they pick bugs and debris out of their companions' fur

Across species, more grooming enables stronger relationships and larger group sizes

The most social non-human apes spend about 20% of their time grooming

Humans don't do nearly as much grooming as other apes, and even if we did, we couldn't possibly afford to do it enough to build groups of 150+ individuals

Enter language:

"Not only can speech be combined with almost every other activity, but it can also be used to address several different individuals simultaneously."

Compared to physical grooming, language is *insanely* scalable and efficient as a vector for social bonding

In addition to gossip/storytelling, humans also facilitate group cohesion through several other unique verbal and sub-verbal activities, including writing, singing, dancing, and laughter

Altogether, Dunbar estimates that our tools are 2-3x more effective than social grooming

I think language v. grooming is the thing that distinguishes us most from other apes—and the thing that makes it easiest to understand our primate ancestry https://twitter.com/choosy_mom/status/1222251506331553793?s=20

While it's impressive to understand how effective we are at creating large social graphs, it's important to remember that human communities are a means to an end: longevity, health, and well-being

The volume/quality of your social relationships is predictive of a wide range of physiological and mental health outcomes—isolation is a sickness in the literal sense https://twitter.com/choosy_mom/status/1221616773159505920?s=20

A lot more to talk about here, but I'll end the thread with this very real graph from Dunbar's 'Anatomy of Friendship' (2017), my favorite academic paper of all time

@scienceshitpost