If you’ve read any network theory, you’re probably familiar with Dunbar’s Number, or the idea that groups tend to fall off quickly in effectiveness and cohesiveness once they exceed approximately 150. The finding came from some anthropological research originally, and leading companies such as W.L. Gore have used Dunbar’s number as the ceiling for work group sizes and to aid in efficiency and team collaboration. But what about your “personal” Dunbar number? When considering social media, you may have an overlapping group of friends from Facebook, Twitter, Linkedin, Email, and other places — but where’s the operative or active group?  Is the overall number of connections higher than 150, or does Dunbar’s theory still hold?

I believe that Dunbar’s number is still relevant in the context of social media, but that it is a constantly changing set.  Dunbar’s number for social media comprises the ~150 most important people in each overlapping social set with whom you stay in contact. Given that social sets move and reconfigure, it’s reasonable to hypothesize that I might have a set of 150 most important people in Facebook, 150 people whom I read most on Twitter, 150 people with whom I correspond most on email, etc. But as it turns out, the number isn’t 4 x 150 after all: it’s just a lot closer to the 150 people you most care about at the moment, depending upon where and how you spend your time on and offline.   So you can connect with more than 150 people, but it’s hard to believe that you can stay engaged meaningfully with more than 150 people at a time.

A disclaimer: I work at Gist, where I think about how to make users of our service more successful. I’ve noticed when using Gist (and when using other tools) that the number of people I communicate with meaningfully on a regular basis isn’t as high as I thought. Dunbar’s number notwithstanding, I’m a pretty connected person and I thought that between my various connections I was communicating with many more people on a regular basis. It turned out that I am communicating with a lot of Gist users and with my established networks. But the difference I didn’t see as clearly before was that this personal connection (the Personal Dunbar Number, if you will) varied by recency of communication, importance of the person in my overall network, and by the other groups with which I’m communicating.  In any given period of time I don’t communicate with a larger set than 150 or so people, but the time between periods of communications is dropping, and the reach of these communications is increasing.

Because I can learn more about the news published about and by the most important people in my network, and because it’s easy to change that focus depending upon the facet of the network I’m viewing, my “Personal Dunbar Number” is growing and is larger than 150 people.  But there’s a catch — I don’t know if the people on the other end of the network feel the same way — and look forward to finding out the answer to that question in the coming months.  In the meanwhile, I will be trading time for insights and using social media tools like Gist to help me share these insights with the most valuable people in my network.