I initially read this as ‘Dunbar Number’ (which I fully expect to be able to say several times this evening).
“Dunbar is an anthropologist at the University College of London, who wrote a paper on Co-Evolution Of Neocortex Size, Group Size And Language In Humans where he hypothesizes:
... there is a cognitive limit to the number of individuals with whom any one person can maintain stable relationships"http://www.lifewithalacrity.com/2004/03/the_dunbar_numb.html





