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Social media: Communities inside networks? Networks inside of communities?

5th Sep 2011
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As part of a new series, Michael Wu, principal scientist of analytics at Lithium Technologies, shares research findings on the relationship between social networks and communities. In the latest part of this series, Michael discusses the social anthropology of online communities and social networks.

I’ve previously written about the difference between communities and social networks and their distinct roles in building and maintaining relationships. In those posts we examined the structure of communities and social networks in isolation. In reality, however, they coexist and overlap each other – at any given time we are part of many communities, and are connected to people in these communities as well as those beyond our communities.

Today I will give you a unified view of communities and social networks in an attempt to understand how these two social structures fit together. This post is a little more abstract and theoretical in nature – in comparison to previous posts – but I believe it will give you a novel perspective on the inner workings of social media.

The social networks inside communities

As we’ve learned, most of the strong relationships in our personal social network (a.k.a. personal network) were developed in communities that were once part of our lives. Figure 1 illustrates the dynamics of a person (hypothetically Bob, the red dot in Figure 1) joining a community (yellow).

From personal experience, you probably recognize the fact that when someone joins a community, the rest of his personal network does not necessarily join with him. That is, your friends generally do not follow you everywhere, at least not immediately, and not all of them. Why is this? The main reason is because people have different interests and they have communities of their own. Upon joining the community and interacting with other community members, Bob would create weak ties (dotted lines). If the interactions were mutually desirable and have the proper environment to develop over time, then some of these emerging weak ties will grow into strong relationships, which will ultimately become part of Bob’s personal social network.

As you can see, it is definitely possible to have social networks within a community. In fact, social networks will develop naturally in communities that provide a rich medium for their members engage and interact. Members who have invested much time and effort in the community will tend to have a more extensive network (e.g. the orange dots), whereas new members (e.g. the red dot) will tend to have fewer connections. But this is just one part of Bob’s social network (i.e. the localized social network inside this particular community).

In reality, the picture is more complicated. Because Bob, like most people, doesn’t just belong to one community. Most people are part of several communities at any given time. Figure 2 illustrates this situation, where Bob is actually part of three other communities (blue, green, and orange). Note that within each of these communities, there are actually complex network structures just like the yellow community, but we’ve kept these redundant details hidden.

The communities inside social networks

Although the entire social network covers the globe, your personal network (which includes only your direct connections) is more limited in scope. This means we can examine Bob’s network in greater detail. Since this section focuses on Bob’s personal network, we will hide all the relationships that are not directly connected to Bob. As we discussed in the previous section, Bob has just joined the yellow community, he didn’t know anyone in this community before and hasn’t established any long term relationship yet. So if we hide the details and only look at Bob’s personal network, he actually has no connections in the yellow community.

However, Bob is already a member of three communities, so we can examine the relationships that Bob has established in these communities. Figure 3 shows all of Bob’s friends and the communities they belong to (the black lines indicate direct connections to Bob). It is not surprising to see that Bob has friends in the blue, green and orange community. Moreover, one of his friends (the blue dot) shares two common communities (blue and orange) with Bob. Notice that Bob also has friends that do not share any communities with him. These friends are in the pink, violet, and cyan community respectively. Where do these friends come from?

Remember, as we grow and our lives change, it is natural for people to move away from a community and move into another. Since we maintain the relationships we established in communities with our social network, it is therefore logical to find relationships across community boundaries. This means sometime in the past, either Bob has left the pink, violet, and cyan communities, or his friends have left their common communities and then subsequently joined the pink, violet, and cyan communities.

Now that we understand the community structure around Bob, we can begin to fill in the network structures. Figure 3 is incomplete because it doesn’t show how Bob’s friends are interconnected among themselves. If none of Bob’s friend knew each other, then this picture would be correct. However, this is unrealistic, because the social dynamics (such as the triadic closure rule, homophily, etc) that govern tie formation tends to create cliques among friends.

This brings us to Figure 4, which shows the structure of Bob’s personal social network, and how it fits with the community structure around him. The black lines are Bob's direct relationships, and the gray lines are connections among Bob’s friends. Together they make up Bob's personal network. What do you see inside this network? Do you see communities? Not only will you find communities within personal networks, communities exist inside the global social network too. This will be more obvious if you recognize the fact that the global social network includes everyone in the world. Consequently, any community consisting of a subset of the world’s population must lie inside this global network.


So what have we learned? Although the topological structure of communities and social networks are very different, and each social structure has its unique functions in human history, they are tightly interwoven. In fact they complement each other.

  1. Social networks develops naturally inside communities (e.g. Friends on Yelp)
  2. Communities can (and often do) exist inside social networks (e.g. fan pages and groups on Facebook)

We have examined the social structure around a hypothetical person, Bob, and it looks something like Figure 4. But this is only for one person. What is not shown in this picture is that everyone of Bob’s friend has a similar social structure around him/her. This also applies to all the people inside the communities that weren’t shown, because they weren’t directly connected to Bob. In fact, these social structures exist around every single human being on earth. The complexity is truly perplexing, yet beautiful.

Alright, now that we (hopefully) have a more holistic understanding of community and social network, as well as how they fit inside each other, we can begin applying it. Next time, we will use this knowledge to analyze an interesting social media platform – Twitter. But, before that, maybe we can have some discussions around this topic. Comments of any kind are always welcome, so keep them coming.

Michael Wu, Ph.D. is  the principal scientist of analytics at Lithium Technologies. Michael was voted a 2010 Influential Leader by CRM Magazine for his work on predictive social analytics and its application to social CRM. You can follow him on Twitter at mich8elwuThis post originally appeared on the Lithosphere.

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