Tobias Escher at the OII

Last Wednesday I had the pleasure to take part in the Social Sciences dinner of the Keble College Social Sciences Group. Over good food and wine, Professor Robin Dunbar (now at Oxford) gave an enjoyable talk about the number that made him famous: 150.

The so-called Dunbar’s number was prominently featured in the book The Tipping Point and is basically the average size of a social group that is still somehow manageable for a human. Or to put it simply: Your brain can just deal with about 150 meaningful relationships. While the number has caught on, it is more a statement about how much social complexity the brain can deal with.

Once he and his team came across this number and were looking for confirmation, they found a number of examples in which something around 150 seemed to be a recurring pattern for manageable group sizes of people. His examples included:

• the average village size in the Domesday Book
• the ideal size for church congregations
• the common size of the smallest self-sustainable militar unit, the company
• the maximum number of guild members in some online games
• the religious community of the Hutterites start a new colony when it grows above 150
• Apparently Gore Associates, the makers of Gore-Tex, start a new factory once one has more then 150 workers

Now, the crucial point is obviously what meaningful relationships are and here the definition becomes a bit more hazy. He offered several estimations:

• people you can go to in moments of great distress
• people you to trust and one which you could rely
• people of which you know immediately the position in your overall social network

Within these group size of about 150 they also found a hierarchical structure of friendship which basically means different layers of friendship, from very close friends to more weak ties with people you communicate with less often. Interestingly they observed a scaling factor of three, which means 5 intimate friends (support), 15 close friends (sympathy), around 50 in the next layer and then 150 which according to Dunbar denotes the inner circle of one’s relationships.

They are unsure about the reasons but possible explanations could be either the limits in brain capacity or simply the time requirements of managing relationships. He emphasized that their postulated relation between brain size and group size is only valid for primates because of the pair-bonding behaviour of those species. Apparently it takes a pretty large brain to solve the cognitively demanding task of finding a life-long partner.

Now while this was a really interesting and entertaining talk it left me wondering about what makes good research as well as what makes popular research. Not necessarily assuming that this is a zero-sum game, ie. research that is popular cannot be thorough and vice versa, I was at times struck by how vague the definitions were (e.g. of relationships), how much variation there is in the measured group size and how little justice the fixation on a group size of 150 really does Dunbar’s theory. And yet, it has caught on in the public mind.

Apart from the fact that this topic of relationships is stricking a chord in people I also think it is because Professor Dunbar knows how to make his research appealing to the broader public (see for example his article “Tall men have more reproductive success“). However, I do have my doubts about some of the conclusion drawn from the underlying research. For example, is it really insightful to study 43 individuals and whom they send Christmas cards to? Despite the huge variation of the results and the small sample it is used as yet another pillar that supports the overall theory.

Apart from pondering about what makes successful research – both with peers as well as the public – the obvious question for me is how technologies might change Dunbar’s number. Surely we could assume that for example social network sites help us deal more efficiently with the social complexities of our lifes. There has been a bit of work done for online communities.

Professor Dunbar expects that the general hypothesis is still true but that technology might slow down the decay of relationships. However, he is just in the process of collecting data on this topic with the DETESS project (Developing Theory for Evolving Socio-cognitive Systems) in which they for example equipped final year A-level students with free mobile phones to track their social networks (whom they call and text) in the transition period from school to university.

For now I believe that this theory merits a close re-examination, both for its general validity as well as for its applicability to the network society age. If we could come up with a useful experimental design this could be as ground-breaking a study as Duncan Watts re-examination of the Milgram’s small world experiments. Social network sites seem to be an obvious candidate for such a study but it hinges on the proper definition of relationships.

Let me know if you would be interested in brainstorming together – maybe we could offer some new insights!