Dunbar Lives!

The other day, I talked about the “real” Twitter: the sparse subgraph of meaningful social relationships buried in the far denser follower graph. Well, it turns out that Facebook’s own “in-house sociologist” Cameron Marlow has documented a similar phenomenon on Facebook:

The average male Facebook user with 120 friends:

• Leaves comments on 7 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
• Messages or chats with 6 friends

The average male Facebook user with 500 friends:

• Leaves comments on 17 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
• Messages or chats with 16 friends

Students of sociology have long been familiar with Dunbar’s number, which Wikipedia defines as “the theoretical cognitive limit to the number of people with whom one can maintain stable social relationships”. Others have proposed different limits, but everyone seems to agree that the number is less than 300–something that you might not know from looking at the follower / connection statistics of online social networks.

Of course, this cognitive limit reflects attention scarcity. Wouldn’t it be nice if online social networks did too. I’m trying!