Social brain refreshed

Dr Michael Harre is lead author of the research published in the Journal of the Royal Society Interface.

The researchers from the University's School of Civil Engineering and the newly created Centre for Complex Systems,  looked at what drives the shape of our complex social networks. They believe the process underlying the formation of human social networks has largely been ignored in previous studies.

Dr Harre said: “What our research showed for the first time is that complex layers of social groups are formed by adding one more person to our 'friends' list. And much like the ripples in a pond after you throw in a stone, the strength of each connection diminishes or weakens as they expand out.

“We start with our life partners and best friends and extend to distant acquaintances. Each friend added is slightly more distant than those from the inner circles.

“Previously, thanks to British anthropologist and evolutionary psychologist Robin Dunbar, it was conjectured that our brains developed to the size they are to enable us to deal with the social complexity of other humans. We also knew that the size of our social groups are limited on average to a largest circle of around 130 -150 people. Our findings show that maintaining about five links, one for each social layer, is sufficient to support complex social networks of that size.”

Dr Harre says that all of this becomes important when we consider the dynamic process of group formation.

“When ‘small families’ of say four people join to form a larger ‘extended family’ of around 13-14 people, on average only one more connection per person is needed. 

“When ‘extended families’ merge into ‘clans’ of say 40-45 people again only an average of one connection per person needs to be added. Finally, when ‘clans’ combine to form the largest groups of ‘tribes’ of approximately 130-150 people, again only one connection per person on average needs to be added. 

“These results show that it is sufficient to add an average of just one connection per person to increase the size of the group roughly three-fold at the next largest social layer.  

“However, beyond these group sizes our brains find managing the complex social interactions too difficult and it is easier for us to manage hierarchical organisational structures,” Dr Harre said.

The researchers used data from two previous large scale studies to look at these two well-known models of social connectedness: the hierarchical dominance model which applies to corporations, military organisations and ape communities; and ‘Erdös-Rényi’ networks that represent self-organising or grass roots communities similar to those of our hunter-gatherer forebears.