Constraints on Group Size in Social Networks

How many people do you know? OK, not Brad and Angelina - but really KNOW - interact with directly and be influenced by? How many people can you know? After all we are all constrained by time - so there would seem to be limits to how many people we can interact with socially on a productive and regular basis.
Imagine living in a small village or being part of an autonomous tribe where each member has a role to play in achieving group objectives (the butcher, the baker, the candlestick maker; tinker, tailor, soldier, sailor). In this hypothetical village there are five sets of grandparents (10 people), each has given rise to three married adults, and these in turn have three children of their own. This modest group is 85 individuals. This five-family village seems intuitively about as small as a community can get and still be viable (I am not offering any evidence for this just yet - I hope you'll agree that it is at least plausible). If we expand the model to a core group of nine grandparents, with the same average number of married offspring and children, it will lead to a village with about 153 members, and so on as shown.

The relationship between the number of families in the community (with kinship to the core grandparents) and the amount of time available for social interaction on a daily basis is as follows.

What matters here is the overall shape of this curve - as the community size increases the time available for building bonds of cohesion, and social grooming between community members, decreases dramatically. Up to five families there is so much time available that it may seem like the community is truly just "one big family". But, at some point (around 9 families) there is a subtle transition where individuals will have to consciously/unconsciously decide to socially groom and bond-with members of a sub-group (their kin) rather than the community at large.

Surprisingly (to me it was VERY surprising) this line of thinking is supported by a wide selection of examples from the real world. A lot of this has been captured in a beautiful paper by Robin Dunbar from University College London (google him).

Reference - Robin Dunbar "Neocortex size as a constraint on group size in primates"

One quote from this paper -
"...the reason given by the Hutterites for limiting their communities to 150 is particularly illuminating. They explicitly state that when the number of individuals is much larger than this, it becomes difficult to control their behavior by peer pressure alone. Rather than create a police force they prefer to split the community. Forge (1972) came to a similar conclusion on the basis of an analysis of settlement size and structure among contemporary New Guinea "neolithic" cultivators. He argued that the figure of 150 was a key threshold in community size in these societies. When communities exceed this size basic relationships of kinship and affinity were insufficient to maintainsocial cohesion; stability could then be maintained only if formal structures developed which defined specific roles within the group. In other words, large communities are invariably hierarchically structured in some way, whereas small communities are not."

Pretty clearly this presents opportunities for modern Social Networking tools to intelligently identify, strengthen and support working teams and communities of practice.