LinkedIn and Dunbar’s Number

The fact I avoid much of the social networking that takes place on the Internet is a feature, not a bug. MySpace and Facebook look like blogging with cool features that someone else controls. As for Twitter, I think Joel Spolsky (2010) has it about right,

Although I appreciate that many people find Twitter to be valuable, I find it a truly awful way to exchange thoughts and ideas. It creates a mentally stunted world in which the most complicated thought you can think is one sentence long. It’s a cacophony of people shouting their thoughts into the abyss without listening to what anyone else is saying. Logging on gives you a page full of little hand grenades: impossible-to-understand, context-free sentences that take five minutes of research to unravel and which then turn out to be stupid, irrelevant, or pertaining to the television series Battlestar Galactica.

I am exploring Google+, however, and maintain a LinkedIn account. The former because there are several features which interest me from an e-learning and collaboration perspective. The latter because, so far, it is the only one that makes sense given my interests and goals. The rest pretty much fits in with Spolsky’s assessment of Twitter – zettabytes of storage for uninteresting chatter.

For those interested in doing more than just going along with the latest craze, there is the realization that strategic participation in any social network requires a measure of preparation and ongoing maintenance. Signing up and posting impulsive or stream-of-(un)consciousness blather is the path to unpredictable results. If there were a predictable result, it might be that your following would reflect the least common denominator from the pool of social network participants rather than valuable contributors to your social network strategy. That’s probably a best case scenario. For a glimpse of what the worst case might look like, consult Anthony Weiner (D-NY, ret.).

So social networks need attention if they are to remain viable and avoid a steady decay into a stale presence. This means they demand time, a precious resource for any working individual. If someone is busy earning a living (i.e. “successful”), they’re less likely to join or maintain an online social network presence. If work keeps them less busy, then they may have an enhanced and robust online social network presence. There are, of course, various degrees of involvement across this spectrum and most people slide back and forth depending on circumstances.

These are some of the things to keep in mind when evaluating other people’s online social network presence. A case in point is the roster of connections people collect on LinkedIn

I understand the purpose of building a roster of connections. However, in many cases it looks to be more a score for popularity than a useful indication of one’s sphere of professional influence. For individuals with 500+ members on their roster of connections, to what degree of certainty can they claim valuable insight into the character and capability of each of those connections?

The answer to this may lie with Dunbar’s Number, named for the British anthropologist Robin Dunbar and the research he completed to arrive at the number. Gladwell (2000) refers to this number as the “social channel capacity” (p. 177) and he describes it as follows:

Dunbar’s argument is that brains evolve, they get bigger, in order to handle the complexities of larger social groups. If you belong to a group of five people, Dunbar points out, you have to keep track of ten separate relationships: your relationship with the four others in your circle and the six other two-way relationships between the others. That’s what it means to know everyone in the circle. You have to understand the personal dynamics of the group, juggle different personalities, keep people happy, manage the demands on your own time and attention, and so on. If you belong to a group of twenty people, however, there are now 190 two-way relationships to keep track of: 19 involving yourself and 171 involving the rest of the group. That’s a fivefold increase in the size of the group, but a twentyfold increase in the amount of information processing needed to “know” the other members of the group. Even a relatively small increase in the size of a group, in other words, creates a significant additional social and intellectual burden. (p. 178-179)

This number, according to Dunbar, is approximately 150.

The figure of 150 seems to represent the maximum number of individuals with whom we can have a genuinely social relationship, the kind of relationship that goes with knowing who they are and how they relate to us. Putting it another way, it is the number of people you would not feel embarrassed about joining uninvited for a drink if you happened to bump into them in a bar. (as cited in Gladwell, 2000, p. 179)

Research seems to support this theory, with a variance of ± 50, across a diverse set of social structures from primitive to modern. Using the number 150 puts the edge of the envelop for maintaining genuine relationships at somewhere around 11,175. For those with 500 connections on LinkedIn, that number rises to 124,750, a number likely well beyond the capacity of even the most dedicated social butterfly to maintain in any meaningful way. The further one goes beyond the 150 connection limit, the greater the likelihood that individual’s collection of connections has become dilute with increasingly weak linked connections.

The conclusion to be drawn is that individuals with 500+ connections on LinkedIn either have a great deal of kruft built up in their rosters or they connect to anyone who sends them an invitation – more like collecting a point rather then gaining a meaningful connection. Regardless, it is difficult to make a general case for how such a large number of connections is of value on a social network such as LinkedIn. Specific cases could be made in instances where popularity is a business asset (performance artists and human resource professionals, for example) and in such cases, social networks such as Facebook may serve the individual better.

So where is the value in running a roster of connections up to 500+? What is the value of including individuals with such heavy rosters on one’s own roster of connections? There are several on my profile, but I know each of them personally.

From a complex systems perspective, insight might be gained by considering LinkedIn connections as formal network nodes. We can identify nodes (people) and edges (the relationships between them.) But calculating the degree of each node and path length is problematic as LinkedIn and individual users control the visibility of nodes. The value of any individual node’s roster of connections cannot be independently calculated.

Considered as small-worlds networks, the LinkedIn connection rosters make more sense. As a new user begins constructing their individual connection roster, it likely consists of a non-random cluster of close friends and associates. As it grows, they begin to add individuals with whom they are less familiar or otherwise have a weaker connection. Consequently, LinkedIn connection rosters greater than 150 likely represent weakly emergent, small-worlds networks within a cloud of random friends, weak acquaintances, and strangers with whom the node might share one or more professional attributes.

How this is of use in a business oriented social network remains elusive to me. If I ask for an introduction to a second degree connection, what is the likelihood it will be be picked up? Viewed from the perspective of complexity theory and based on experience, I’m likely to find greater benefit by focusing on local business associations and industry specific conferences in which I can randomly choose someone to whom I wish to introduce myself directly.


Gladwell, M. (2000). The tipping point: How little things can make a big difference. New York, NY: Bay Back Books

Spolsky, J. (2010, March 14). Puppy! Retrieved from