Relationship Limits in Social Networks

by Luke Wroblewski October 15, 2009

Several years ago an anthropologist named Robin Dunbar concluded that the “cognitive power of the brain limits the size of the social network that any individual or species can develop.” Dunbar suggested that the size of the human brain only allows for stable networks of 148 people to develop. His famous “Dunbar number” (often rounded to 150) states that there is a cap on the attention we can give to social relationships.

But do these relationship limits exist in online social networks? Are they influenced by the dominant social model (1-way, 2-way, group, etc.) on a given site? Looking at data from Twitter (1-way relationships), and Facebook in 2004 (when it was all college students) and 2009 (2-way relationships), it seems a similar set of relationship limits do exist.

  • 120 average number of friends per user on Facebook in Feb 2009
  • 144 average on Facebook from 2004 to March 2006
  • 92.4% of people on Twitter follow less than 100 people

While some people do accumulate more than 150 connections in both of these sites, many of these relationships lack social significance and matter only for broadcasting (audience reach) or gaming.

For more insights from online social relationships, check out my complete Impact of Social Models presentation.