#Dunbarsnumber – the idea that a person can only have a limited number of close relationships, probably around 150.


[O]ur minds are not designed to allow us to have more than a very limited number of people in our social world. The emotional and psychological investments that a close relationship requires are considerable, and the emotional capital we have available is limited.

Indeed, no matter what Facebook allows us to do, I have found that most of us can maintain only around 150 meaningful relationships, online and off — what has become known as Dunbar’s number. Yes, you can “friend” 500, 1,000, even 5,000 people with your Facebook page, but all save the core 150 are mere voyeurs looking into your daily life — a fact incorporated into the new social networking site Path, which limits the number of friends you can have to 50.

What’s more, contrary to all the hype and hope, the people in our electronic social worlds are, for most of us, the same people in our offline social worlds. In fact, the average number of friends on Facebook is 120 to 130, just short enough of Dunbar’s number to allow room for grandparents and babies, people too old or too young to have acquired the digital habit.

See article at: NYT 26Dec10: “You’ve Got to Have (150) Friends” Op-Ed by Robin Dunbar, professor of evolutionary anthropology at Oxford and the author of “How Many Friends Does One Person Need? Dunbar’s Number and Other Evolutionary Quirks”


Twitter’s executives talk about the “Dunbar number” — the maximum number of people, generally believed to be 150, with whom one person can have strong relationships. This effort, mind you, comes from a company with a business model that fosters a multitude of ever-growing — and largely glancing — interactions among Twitter’s users.    

“I’ve never seen a company so focused on avoiding the Dunbar number,” says Adam Bain, who recently joined Twitter from the News Corporation as head of global revenue. “You can tell Ev [Evan Williams, co-founder of Twitter] planned it out.”    

Each time employees log on to their computers, for instance, they see a photo of a colleague, with clues and a list of the person’s hobbies, and must identify the person. And notes from every meeting are posted for all employees to read.

See article at: NYT 31Oct10: “Why Twitter’s C.E.O. Demoted Himself”

     **********************************************************        [T]he evolutionary anthropologist Robin Dunbar[‘s] . . . eponymous number is 147.8, plus or minus a lot, and it is the size of the average human being’s social network of friends, as predicted by the size of the average human brain.

Many years ago Mr. Dunbar famously noticed that there is a tight correlation between the size of a primate’s brain and the size of the social group its species generally forms. On this basis human beings should live in groups of around 150. The neat thing about this prediction was the way it seemed to fit the number of good friends most people have, as measured by the length of address books, the size of hunter-gatherer bands, the population of neolithic villages and the strength of army units. In recent years, Facebook has also seemed to confirm the hunch, with rosters of friends often settling around the Dunbar number.


See article at: WSJ 12-13Feb11 – How Many Friends Can Your Brain Hold? Column by Matt Ridley