This dissertation deals with the analysis of interpersonal communication dynamics in online social networks and social media. My central hypothesis is that communication dynamics between individuals manifest themselves via three key aspects: the information that is the content of communication, the social engagement i.e. the sociological framework emergent of the communication process, and the channel i.e. the media via which communication takes place. My approach to developing a comprehensive understanding of these aspects in this disseration is essentially computational as well as empirical: I present characterization techniques, develop computational models and finally discuss large-scale quantitative observational studies for each of these organizing ideas.

Communication dynamics have been of interest to researchers from multifaceted domains over the past several decades. However, today there are several modern capabilities encompassing a host of social media websites. These sites feature variegated interactional affordances, ranging from blogging, micro-blogging, sharing media elements as well as a rich set of social actions such as tagging, voting, commenting and so on. Consequently, these communication tools have begun to redefine the ways in which individuals exchange information, their modes of social engagement, and mechanisms of how the media characteristics impact their interactional behavior. Additionally, there are accompanying challenges regarding the nature of the communication itself. For example, it is often temporally volatile, allows an inexpensive expanse and reach to a broad audience and typically involves high reciprocity from a wide and demographically diverse population. This dissertation is geared towards developing methods, tools and frameworks towards understanding such key issues and at the same time addressing the associated challenges of making sense of the modern online communication processes.

The outcomes of this research are manifold. I present the contributions in three parts, corresponding to the three key organizing ideas. First, it is observed that user context is key to characterizing communication between a pair of individuals. However interestingly, the probability of future communication seems to be more sensitive to the context compared to the delay, which appears to be rather habitual. Further, it is observed that diffusion of social actions in a network can be indicative of future information cascades; that might be attributed to social influence or homophily depending on the nature of the social action. Second, it is also observed that different modes of social engagement lead to evolution of groups that have considerable predictive capability in characterizing external-world temporal occurrences, such as stock market dynamics as well as collective political sentiments. Finally, characterization of communication on rich media sites have shown that conversations that are deemed “interesting” appear to have consequential impact on the properties of the social network: in terms of degree of participation of the individuals, thematic diffusion as well as emergent cohesiveness in activity among the participants in the network. Based on all these outcomes, I believe that this research can make significant contribution into a better understanding of how individuals communicate online and how it is redefining the collective sociological behavior.