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richer visualizations of social network ties
14 october 2003

"The imaginary friends I had as a kid dropped me because their friends thought I didn't exist." - Aaron Machado

Standard social network visualizations do not typically focus on the nature of relations or ties between individuals; thus, a single directional edge is often used to connect two person nodes. This edge does not represent the strength of the relation, or its nature. Are these two people co-workers, activity buddies, lovers? Is the relation recriprocal or one sided? To be fair to those researchers who devised these visualizations, the data given to them is probably representative of one only relation. Even if the data allowed for multiple relations to be known, it would probably be confusing to encode and display multiple relations, particularly in a large network; whereas a keep-it-simple approach could eschew the uninterpretability of the visualization. However, if we were to visualize the multiplexity of social ties, important patterns might emerge.

In "Studying Online Social Networks," Garton et al. positions the deconstruction of social ties into bundles of disparate, directional relations as being key to understanding how individuals cluster in social networks, how these clusters overlap, and how clusters endure or fall apart. A key concept is the simplexity versus multiplexity of social ties. If a social tie features many different types of relations (e.g. co-workers, one tutors the other, watch baseball together), and if many of these relations are mutual, then the tie is known as a multiplex tie, and can be seen as durable. The durability of a single tie can impact the larger social network; for example, if a particular person is at a cut-point point and a tie is broken, a large subset of the network may drop out. It is also understood that individuals who are capable of relations not possessed by other members of his/her group or organization may serve the all important social role of gatekeeper.

The aforementioned reasons make a compelling case for the inclusion of the simplexity/multiplexity of ties in social network visualizations. In the following sketch, we propose a way of including information about multiplexity into social networks, being sensitive not to overload the network visually.

Figure 1. Social network visualization, with emphasis on multiplex ties,
cut-points, group stability, the potentiality of ties, and gate-keepers.

Squares represent individuals, colors code for the possession of certain social currencies, which may be of a general nature such as physical desirability and intelligence, or of a specific nature such as devotion to a church, devotion to work, devotion to a hobby, membership in a class, etc. The thickness of ties between individuals are indicative of the multiplicity of relations shared, not the scalar magnitude of a single shared relation. We can analyze the utility of such a visualization as follows. The more colors possessed by an individual, the bigger is his/her capacity to form multiplex relations. Because the boldness of lines represents multiplexity and not magnitude, not only can we identify groups but we can comment on the stability of these groups. The color coding also helps us identify the gatekeepers in a group. For example, suppose the red squares represented individuals in a church, and the lime squares represented individuals in politics. We can see that the red-lime squares and the rainbow squares are the gatekeepers who control the flow of information/influence from politics to the church, and vice versa. Cut-points can also be identified. For example, in the center of the sketch, a red/lime square is weakly tied to a teal/lime square. This is a potential cut-point because even at their maximum potential for ties, they can only be weakly linked, having only one compatible color. Contrast this to the red-lime square weakly connected to the rainbow square at the bottom-middle. Although this is a weak link, there is more potential for the link to be strong, so there is hope that this is not in danger of becoming a cut-point.

In the above visualization, we do not consider asymmetrical relations, unreciprocated relations. However, we note that unreciprocated relations are unstable. There must be some social currency exchanged. If for example, "John admires Mary, but Mary hates John," then the relation is rather doomed. In an animation of the above visualization, we might illustrate unreciprocated relations are pulsating between existing and not existing. If there is already a multiplex tie and only one relation is pulsating, it would hardly be visible. However, consider that the above visualization was an egocentric display of one's own social network. If a simplex tie is pulsating and it happened to occur at a cut-point, we can imagine an entire chunk of one's social network pulsating in and out, thus illustrating cut-points.