“Dunbar’s number is a suggested cognitive limit to the number of people with whom one can maintain stable social relationships—relationships in which an individual knows who each person is and how each person relates to every other person”.
Corollary: any group size approaching 150 people (Dunbar’s number) includes at least one person who knows about Dunbar’s number.
To paraphrase a classic joke, “How do you know if someone knows about Dunbar’s number? They’ll tell you!” I’m telling you, right now, I know about Dunbar’s number. 🙃
Practically, I think this implies:
- If you’re designing an organization close to but not exceeding Dunbar’s number, you can hand-wave the details of when it grows to exceed Dunbar’s number. Someone will enthusiastically let you know that the organization has exceeded Dunbar’s number and might need reconsideration. 🥸
- For organizations as small as 10% of Dunbar’s number (15), there’s a pretty dang good chance that someone knows about Dunbar’s number. For organizations any multiple of that size, you don’t need to go around telling everyone about Dunbar’s number. Chance are, someone is telling everyone about Dunbar’s number. 😆
My experience in (software) teams is there are breakpoints far smaller than Dunbar’s number that matter even more.
| Team/org size | What changes? |
|---|---|
| 3 people | Working consensus/quorum is now a thing. |
| 6 | Super-linearity of personal lines of communication becomes noticeable. |
| 10 | Splitting into teams and managing communications along those lines makes sense. Congrats, you have invented hierarchy and management! |
| 25 | You may not talk to everyone in any given week. Organizing get-togethers takes more than a person-week of effort. |
| 50 | There are a few people who, despite best intentions, you don’t know they exist or what they do. |
| 100 | An old guard/new guard dynamic may form. |
| 150 | Dunbar’s number |
| 500 | You have one weekly ceremony/routine that is necessitated by the organization reaching some kind of IT scale/process. You daydream about the times when you didn’t have to do this every single week. |
| 1500 | All-hands company get-togethers resemble full-blown conferences. |
| 15000 | There are so many possible “left doesn’t know what the right hand” is doing scenarios that it makes my head hurt. |
FWIW, these are all folk rules. I haven’t seen rigorous work that backs any of this up!
