Twitter, Facebook: How Many People Can You Follow?

Twitter and Facebook make it easy to rack up a huge stable of friends and followers, but the number of people who really matter to you may be limited by the size of our brains.

Facebook’s “in-house sociologist”, Dr. Cameron Marlow, recently shared some data with The Economist on how the site’s users interact. Marlow says the average number of “friends” in a Facebook network is 120. The range is large, as you might imagine (234 for me), and women tend to have somewhat more Facebook friends than men.

What’s interesting is that that number of 120 is close to “the Dunbar number” of 150. The Dunbar number is named after anthropologist Robin Dunbar, who has suggested that the human brain can handle a stable network of about 150 people. Groups larger than that number need more restricted rules and laws to maintain a stable group. The Dunbar number is also mentioned in Malcolm Gladwell’s The Tipping Point, as a suggested ideal size for a working group.

But Facebook’s Marlow also looked as the number of people who someone frequently interacts with, and found that number to be small and stable: seven for the average male user and 10 for the average female. So although you may have built up a huge number of friends or followers, your core network — the people you interact with and are close to — remains as small as ever.