Social skills 'down to brain size'
Making friends and being popular may boil down to the size of your forebrain, a study has suggested.
Scientists found an association between the size of the orbital frontal cortex - the part of the brain just above the eyes - and the number of friends a person has. The region is known to be crucial to social skills and the ability to "mentalise", or guess what other people are thinking.
Brain scans revealed that volunteers with the largest numbers of friends also had the largest orbital frontal cortex. The study confirms the link between "mind-reading" skills and the ability to maintain a circle of socially significant friends, as opposed to acquaintances.
Lead researcher Professor Robin Dunbar, from the Institute of Cognitive and Evolutionary Biology at Oxford University, said: "'Mentalising' is where one individual is able to follow a natural hierarchy involving other individuals' mind states.
"For example, in the play Othello, Shakespeare manages to keep track of five separate mental states... Being able to maintain five separate individuals' mental states is the natural upper limit for most adults.
"We found that individuals who had more friends did better on mentalising tasks and had more neural volume in the orbital frontal cortex, the part of the forebrain immediately above the eyes.
"Understanding this link between an individual's brain size and the number of friends they have helps us understand the mechanisms that have led to humans developing bigger brains than other primate species. The frontal lobes of the brain, in particular, have enlarged dramatically in humans over the last half million years."
The research appears in the journal Proceedings of the Royal Society B. A total of 40 volunteers agreed to have magnetic resonance imaging (MRI) brain scans at the University of Liverpool. Participants were also asked to list everyone they had engaged with socially, not professionally, over the previous seven days, and they also took a psychological test of their mentalising ability.
Psychologist and co-author Dr Joanne Powell, from the University of Liverpool, said: "Perhaps the most important finding of our study is that we have been able to show that the relationship between brain size and social network size is mediated by mentalising skills."
Prof Dunbar added: "Our study finds there is a link between the ability to read how other people think and social network size."