Lately I’ve been noticing the spread of a meme regarding “Dunbar’s Number” of thesis groupmates that I believe is misunderstanding of his ideas. Dunbar supports this hypothesis through studies by a number of field anthropologists. Dunbar then correlate those group sizes to the brain sizes of the primates to produce a mathematical formula for how the two correspond.
Using his formula, which is based on 36 primates, he predicts that 147. However, Dunbar’s work itself suggests that a community size of 150 will not be a mean for a community unless it is highly incentivized to remain together. My suggestion, then, is that language evolved as a “cheap” form of social grooming, so enabling the ancestral humans to maintain the cohesion of the unusually large groups demanded by the particular conditions they faced at the time. However, it does show that for a group to sustain itself at the size of 150, significantly more effort must be spent on the core socialization which is necessary to keep the group functioning. Some organizations will have sufficient incentive to maintain this high level of required socialization.
In dispersed societies, individuals will meet less often and will thus be less familiar with each, so group sizes should be smaller in consequence. My anecdotal evidence generally seems to support the idea that group sizes will usually plateau at a number lower than 150 participants. This comes from 20 years of doing facilitation both on and offline, running several software companies, and running various forums at America Online. Online Communities Ultima Online provides one of the best examples of what sizes an online community will support because it’s well documented and the overall game size is large enough to generate many smaller communities. We have allegiances in the hundreds and even thousands of members, but most of those members are inactive, non-participatory in the group on a regular basis or are mule accounts for farming XP. It is rare to have more than 40 or so active participants in an Allegiance.
I’ve seen similar limits myself in some of the small online games that Skotos produces. We have had some games at Skotos that do manage to overcome Dunbarrian social limits, prime among them The Eternal City which regularly exceeds the Marrach community by more then double. Other online communities that I’ve had experience with have been more traditional, and thus more closely met my expectations for Dunbar’s Number acting as a limit rather than a mean. When I managed the Mac Developer’s Forum community on AOL, a forum would start to break down when it reached about 80 active contributors, requiring a forum split before continued growth could occur. These numbers just keep coming up. This all leads me to hypothesize that the optimal size for active group members for creative and technical groups — as opposed to exclusively survival-oriented groups, such as villages — hovers somewhere between 25-80, but is best around 45-50. MAXIMUM number of people that a person could keep up with socially at any given time, gossip maintenance, was 150.
This doesn’t mean that people don’t have 150 people in their social network, but that they only keep tabs on 150 people max at any given point. Expanding Dunbar’s Numbers To open up the discussion a bit, I’d also hypothesize that Dunbar’s Number is just one datapoint in an overall equation describing what group sizes work and what don’t. Working our way up from the smallest group sizes, I think we can find many break points, both above and below Dunbar’s Number of 150. In my experience the smallest viable group size seems to be somewhere in the range of 5 to 9. Notably, often the difficulty of a 2-person business partnership is compared to that of a marriage. A group of 3 is often unstable, with one person feeling left out, or else one person controlling the others by being the “split” vote. A group of 4 often devolves into two pairs.
In my opinion it is at 5 that the feeling of “team” really starts. At 5 to 8 people, you can have a meeting where everyone can speak out about what the entire group is doing, and everyone feels highly empowered. However, at 9 to 12 people this begins to break down — not enough “attention” is given to everyone and meetings risk becoming either too noisy, too boring, too long, or some combination thereof. The chasm that starts somewhere between 9 to 12 people can be especially daunting for a small business. I’ve already noted the next chasm when you go beyond 80 people, which I think is the point that Dunbar’s Number actually marks for a non-survival oriented group. Even at this lower point, the noise level created by required socialization becomes an issue, and filtering becomes essential.
As you approach 150 this begins to be unmanageable. Once a company grows past 200 you are really starting to need middle-management, but often you can’t afford it yet. Much of this is probably predicted by Dunbar’s model, if you add in the non-survival and dispursed community modifiers that I discuss here. Essentially, as we increase group sizes beyond 80, to 150, 200, or even 350-500, we typically do so by breaking larger groups down into smaller ones, and continually reducing community sizes down to the point where they can be understood and managed by people — and so efficiency reasserts itself.