[Updated December 5, 2007: Clarifying commentary about what qualifies as a "weak tie," from The Virtual Handshake Blog.]
In The Tipping Point, Malcolm Gladwell popularized the "magic number" 150 as the maximum number of individuals with whom one can have "a genuinely social relationship." This has all kinds of implications for people obsessed with maxing out the number of friends they have on Facebook or connections on LinkedIn.
This upper limit on social networking is sometimes called Dunbar's Number, after Robin Dunbar, a British evolutionary psychologist. He postulated that 150 is about the maximum number of individuals a community member can relate to cognitively while keeping those relationships productive. A practical upper limit on network size has been bandied about a lot - too much, perhaps - in discussions of online communities. The question for us seems to be:
Can self-organizing social networks - alumni clusters, special interest groups, local clubs and chapters, or online communities - be effective with more than 150 participants?
The answer is: of course. Here's why.
First of all, Dunbar was talking about something very specific: what he really said was related to primate grooming behavior among animals in the wild. Does it apply to humans using electronic tools to network and connect online, or to prune their contacts in their Rolodex?
In a June, 2005 commentary Rosanna Tarsiero answers with a thoughtful "No" and quotes Dunbar:
the relationship between group size and time devoted to grooming appears to be a consequence of the intensity with which a small number of key "friendships" (the primary network - also known as 'close ties within the group') is serviced rather than [of] the total number of individuals in the group....
She emphasizes that Dunbar is only talking about the number of "close ties" among group members decreasing dramatically in quality above 150, but the total group size of the community in which you maintain your 150 close ties can be in the thousands. The upper limit is a qualitative one that describes the strength of connections.
This does still matter. In a seminal 1973 paper, Mark Granovetter said, in effect, that the most valuable reason to maintain a network of strong ties is to have access to a network of weak ties. In describing the "strength of weak ties" Granovetter pointed out that strong ties are less likely to add value to your network, because people you are closely connected to already have the same friends and same resources, and know the same things, as you do.
People who move in circles different from yours are likely to know of opportunities and resources you would never know about. That is the strength of weak ties: access to new information, new people and new networks.
[As an aside, Granovetter acknowledges that merely addressing the strength of connections ignores other important questions - for example, what about the content of those ties? What about negative relationships? Specialization? Hierarchy? And so on. He also points out that weak ties are generally people with whom you shared a strong tie at some time in the past.]
Bottom line for alumni relations: It's interesting to think about Dunbar's proposition in terms of alumni groups such as chapters or clubs, class reunions, and so on. But we'll probably do our constituents more good by educating them about the strength of weak ties, and encouraging them to use the alumni network to reach out to people they used to know well, or whom they don't know - yet.