'How Many Friends Does One Person Need?'


by Robin Dunbar | 04 Feb 10

Robin Dunbar's book cover for How Many Friends Does One Person Need?We are the product of our evolutionary history and this colours our everyday lives - including the number of friends we can have, according to a book published by Professor Robin Dunbar. Robin Dunbar, Professor of Evolutionary Anthropology at the University of Oxford, says 150 is the maximum number of friendships that the human mind is capable of handling. 'Dunbar's number', as it is known, even applies to the Facebook generation.

Professor Dunbar concludes that the volume of the neocortex region of our brain, used for language and thought, limits the number of friends we can maintain. He argues this number has not changed much throughout history and applies in the same way on the web as it does in real life. He even goes as far as to say that anyone who claims to have more is 'suspect', as the quality of relationships deteriorates as the social group widens.

Professor Dunbar's research also explores why gossip is good for us.  His view is that language allows us to integrate a large number of social relationships and one important means of doing this is through the exchange of information about individuals who are not present. Gossip about relationships accounts for an overwhelming proportion of human conversations, and he explains that gossip plays an important part in how we assess others outside our own close group. We can find out from one person how others are likely to behave, how we should react to them when we actually meet them and what kind of relationships they have with third parties.

Professor Dunbar's studies have revealed that, across the birds and mammals, it is monogamous species that have the biggest brains. 'If you need evidence that romantic relationships are hard work,' says Professor Dunbar, 'this is surely it. Relationships require time and effort and a lot of brain work.'

Books asked Professor Dunbar about his research.

How much of your life's research is embodied in the findings of this book?

This book draws mainly on the research that I and my group have been doing over the last decade, in particular. But in many ways the roots of it go back to my early interests in primate social behaviour.

How did you arrive at 'Dunbar's number'? Is this number altered in any way by personality or by whether you live on a remote hillside as opposed to a densely populated city?

I discovered Dunbar's number by extrapolating to humans from a relationship between brain size and social group size that I had discovered in monkeys and apes. The number does not seem to change with social or ecological context, but what does change is whether everyone in your circle lives in the same place (as in rural hilltop communities) or is dispersed across the whole country (as is now more typically the case for modern city dwellers). 

Social networking circles include disparate groups of people who may be close friends or just acquaintances. What quality of friendship are you proposing when you limit this number to 150 friends?

The number 150 really refers to those people with whom you have a personalised relationship, one that is reciprocal and based around general obligations of trust and reciprocity. If you asked them to do a favour, they would be more likely to say yes than those outside the 150. 

Gossip can be very harmful and inaccurate if you want to make accurate assessments about people you don't know very well. Isn't this a flaw in your argument, given your informer may have their own agenda for presenting someone in a particular way? For instance, some gossips are prone to gross exaggeration to make their story more interesting.

It's important to remember that gossip in its original sense means just chatting on the doorstep (it derives from the Old English "god-sib", the peer group equivalent of god-parents). But like everything in life and biology, things that evolve for useful purposes can always be exploited for devious ones: black propaganda is an almost unavoidable outcome of such a form of communication in a species as smart as humans. Interestingly, the word "gossip" only acquired its negative connotations in the eighteenth century. In fact, research suggests that we are quite sensitive to misuse of gossip in this way, and are less likely to believe what someone says if we sense that they are trying to use it to steal a march on the rest of us. 

'How Many Friends Does One Person Need?' is published by Faber on 4 February 2010.