“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.

FWIW, these are all folk rules. I haven’t seen rigorous work that backs any of this up!