Zusammenfassung
The study of human interactions is of central importance for understanding
the behavior of individuals, groups and societies. Here, we observe the
formation and evolution of networks by monitoring the addition of all new links
and we analyze quantitatively the tendencies used to create ties in these
evolving online affiliation networks. We first show that an accurate estimation
of these probabilistic tendencies can only be achieved by following the time
evolution of the network. For example, actions that are attributed to the usual
friend of a friend mechanism through a static snapshot of the network are
overestimated by a factor of two. A detailed analysis of the dynamic network
evolution shows that half of those triangles were generated through other
mechanisms, in spite of the characteristic static pattern. We start by
characterizing every single link when the tie was established in the network.
This allows us to describe the probabilistic tendencies of tie formation and
extract sociological conclusions as follows. The tendencies to add new links
differ significantly from what we would expect if they were not affected by the
individuals' structural position in the network, i.e., from random link
formation. We also find significant differences in behavioral traits among
individuals according to their degree of activity, gender, age, popularity and
other attributes. For instance, in the particular datasets analyzed here, we
find that women reciprocate connections three times as much as men and this
difference increases with age. Men tend to connect with the most popular people
more often than women across all ages. On the other hand, triangular ties
tendencies are similar and independent of gender. Our findings can be useful to
build models of realistic social network structures and discover the underlying
laws that govern establishment of ties in evolving social networks.
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