The famous Dunbar number, or “theoretical cognitive limit to the number of people with whom one can maintain stable social relationships”, is generally accepted to be about 150. However, in a recent interview with The Economist, Cameron Marlow, a research scientist at Facebook, shared some interesting stats on Facebook users’ social behavior patterns.

His findings: while many people have hundreds friends on Facebook, they still only actively communicate with a small few. Or to quote the author of the article, “Humans may be advertising themselves more efficiently. But they still have the same small circles of intimacy as ever.”

Here’s the data from Marlow:

The average male Facebook user with 120 friends:

Leaves comments on 7 friends’ photos, status updates, or wall

friends’ photos, status updates, or wall Messages or chats with 4 friends

The average female Facebook user with 120 friends:

Leaves comments on 10 friends’ photos, status updates, or wall

friends’ photos, status updates, or wall Messages or chats with 6 friends

The average male Facebook user with 500 friends:

Leaves comments on 17 friends’ photos, status updates, or wall

friends’ photos, status updates, or wall Messages or chats with 10 friends

The average female Facebook user with 500 friends:

Leaves comments on 26 friends’ photos, status updates, or wall

friends’ photos, status updates, or wall Messages or chats with 16 friends

In other words, Facebook users comment on stuff from only about 5-10% of their Facebook friends. And as has been shown by many other studies, women communicate with more people in all cases than men.

“People who are members of online social networks are not so much ‘networking’ as they are ‘broadcasting their lives to an outer tier of acquaintances who aren’t necessarily inside the Dunbar circle,'” Lee Rainie, the director of the Pew Internet & American Life Project, says.