"Several years ago ... Robin Dunbar ... concluded that the cognitive power of the brain limits the size of the social network that an individual of any given species can develop. Extrapolating from the brain sizes and social networks of apes, Dr Dunbar suggested that the size of the human brain allows stable networks of about 148. Rounded to 150, this has become famous as the 'Dunbar number'.

"Many institutions ... seem to be organised around the Dunbar number. Because everybody knows everybody else, such groups can run with a minimum of bureaucracy. ... But ... other anthropologists ... have come up with estimates of almost double the Dunbar number for the upper limit of human groups." (The Economist, February 28th 2009)

This research, which has been corroborated by evidence from people's Facebook networks, might apply to us. If we take a value of 210, say, the number of students at each of the other UWCs is just below the Dunbar number, whereas that at AC is well above it: the difference is like that between a very large family and a very small town, which clearly function completely differently.