Ever wonder why you might have more Facebook friends than your peers? Evolutionary anthropologist Robin Dunbar believes he has the answer: the size of your brain.
As the Wall Street Journal reports, Dunbar and his colleagues at Oxford University asked volunteers to write down the initials of every person they had had social contact or communication with over the past week, followed by measuring the volume of their “orbitomedial prefrontal cortex.” No doubt, the size of this lobe of the brain correlates strongly with that person’s number of friends.
(More on TIME.com: Watch The History of Social Networking: An Odd Todd Cartoon)
Dunbar’s “social brain hypothesis” draws from the “theory of mind”– which says that we use our brains to imagine what others are thinking. In short, Dunbar’s team has now found that an abundant social network also associates with the ability to reason about others’ intentions. So, people with more friends are better able to understand perspectives of others. And according to Dunbar, both of these characteristics are well predicted by the volume of gray matter in the prefrontal cortex.
So the next time you hesitate over accepting that friend request on Facebook, remember your end decision may be all down to size.
(More on TIME.com: See Life Inside Facebook’s Headquarters)