Keep Your Friends Close and Your Facebook Friends Closer: A Multiplex Network Approach to the Analysis of Offline and Online Social Ties

Social media allow for an unprecedented amount of inter-action between people online. A fundamental aspect of hu-man social behavior, however, is the tendency of people to associate themselves with like-minded individuals, forming homogeneous social circles both online and offline. In this work, we apply a new model that allows us to distinguish between social ties of varying strength, and to observe evi-dence of homophily with regards to politics, music, health, residential sector & year in college, within the online and offline social network of 74 college students. We present a multiplex network approach to social tie strength, here ap-plied to mobile communication data- calls, text messages, and co-location, allowing us to dimensionally identify rela-tionships by considering the number of communication chan-nels utilized between students. We find that strong social ties are characterized by maximal use of communication chan-nels, while weak ties by minimal use. We are able to identify 75 % of close friendships, 90 % of weaker ties, and 90 % of Facebook friendships as compared to reported ground truth. We then show that stronger ties exhibit greater profile similar-ity than weaker ones. Apart from high homogeneity in social circles with respect to political and health aspects, we observe strong homophily driven by music, residential sector and year in college. Despite Facebook friendship being highly depen-dent on residence and year, exposure to less homogeneous content can be found in the online rather than the offline so-cial circles of students, most notably in political and music aspects