Turns out, most of your 500 Facebook friends don’t really matter to you. Robin Dunbar, a professor of evolutionary anthropology at Oxford University, developed a theory in the 1990s known as “Dunbar’s Number” which claims the size of our neocortex—the part of the brain used for conscious thought and language—limits us to managing around 150 friends, no matter how sociable we try to be. Dunbar found that in the real world people tended to self-organize in groups of around 150 because social cohesion beings to deteriorate as groups get larger. And his preliminary results point to Facebook being no different. “The interesting thing is that you can have 1,500 friends but when you actually look at traffic on sites, you see people maintain the same inner circle of around 150 people,” says Dunbar. So I guess we all have an excuse for not talking to our long-lost friends from second grade.