Brain size to determine whether or not you are good at maintaining friendships?

A recent study has shown that those of us who have a large number of friends, have a larger orbital prefrontal cortex than those of us who lack friends. The research was carried out as part of the ‘Lucy to Language’ project, which was funded by the British Academy and led by Professor Robin Dunbar of the University of Oxford.

The study suggests that to maintain a number of friends we must employ a set of cognitive skills. These skills are described by social scientists as ‘mentalising’ or ‘mind reading’. This ‘mentalising’ skill is seen as the capacity to understand what another person is thinking and it is incredibly crucial to our ability to handle our complex social world, including the ability to hold down conversations with one another.

Anatomical MRI images were taken of the brains of 40 volunteers to measure the size of their prefrontal cortex (the region of high-level thinking). They were asked to write a list of everyone that they had been in social contact with over the previous seven days. They then took a test to determine their competency in mentalising. It was found that the individuals who had more friends, did better on the mentalising tasks and had more neural volume in their orbital prefrontal cortex, which is the part of the forebrain found just above the eyes.

This research is particularly important because it provides the strongest support to date for the social brain hypothesis. This hypothesis is the idea that human brains evolved to accommodate the social demands of living in a big group. Professor Dunbar commented that “understanding the link between an individual’s brain size and the number of friends that they have has helped then to understand the mechanisms that have led to humans developing bigger brains than any other primate species”.