Given that human activities increasingly are mediated by or take place in online environments, we are afforded with novel opportunities for understanding how collective, population-level phenomena and outcomes can be related to individual behaviours. My talk will consider a family of simple generative models to represent the collective behaviour of millions of social networking site users who make choices between different software applications that they can install. The proposed models incorporate two distinct social mechanisms: (1) imitative behaviour reflecting the influence of recent installation activities of other users; (2) rich-get-richer popularity dynamics where users are influenced by the cumulative popularity of each application. Interestingly, although various combinations of the two mechanisms yield long-time behaviour that is consistent with data, the only models that reproduce the observed temporal dynamics well are those that strongly emphasize the recent installation activities of other users over their cumulative popularity. Hence social imitation seems to be especially important in this information rich environment. Methodologically, our work demonstrates that even when using purely observational data, as opposed to experimental research designs, temporal data-driven modelling can in fact under some circumstances effectively distinguish between competing microscopic mechanisms, providing novel insights into collective online behaviour.

This talk is part of the OII Colloquia series that bring senior speakers from other departments at the University of Oxford to the Oxford Internet Institute.

About the speakers

  • Felix Reed-Tsochas

    Saïd Business School & Oxford Martin School, University of Oxford

    Felix Reed-Tsochas is the James Martin Lecturer in Complex Systems and Associate Dean for Research at the Saïd Business School, and a founding Director of the CABDyN Complexity Centre. CABDyN was launched in 2003, and brings together researchers from more than ten University Departments with a shared interest in pursuing a highly interdisciplinary approach to modelling and understanding complex systems and networks across a broad range of application domains. He leads the Programme in Complexity, Risk and Resilience at the Oxford Martin School, and previously co-directed the Programme in Complexity Economics as part of the newly established Institute for New Economic Thinking (INET) at Oxford.

    Felix’s research interests broadly focus on complex networks such as social networks, and the question of how collective behaviours and structures in groups and populations can be related to the decisions and actions of individual agents or actors. In practice, examples of this kind of research range from trying to tease out the role of social influence in determining the popularity of Facebook apps, to understanding how social collateral can strengthen group lending by a microfinance institution in Sierra Leone. In joint work with Robin Dunbar, Felix has also explored how cognitive constraints shape networks of social relationships over time. Applying related network techniques in a medical setting, Felix and collaborators at the NIH have been using large-scale administrative data to understand how the social interactions that patients are exposed to as they move through a hospital may shape individual healthcare outcomes. In applying network methods to financial markets and institutions, Felix has worked on the structure of interbank lending networks with a view to relating structural characteristics to questions of risk and resilience. Similarly, in collaboration with colleagues in the UK and Japan, Felix is developing large-scale maps of global supply chains in the automotive industry, as a first step towards a more systematic understanding of how to think about potential trade-offs between efficiency and resilience. Beyond the social sciences and management, Felix has also worked on problems in theoretical ecology, such as modelling structural changes in ecological networks (i.e. “food webs”) that result from environmental degradation. On the biological side, Felix is also interested in bioinformatics, and has worked on protein-protein interaction networks associated with disease, as part of an effort to develop a novel approach to drug development based on network pharmacology.

    Felix is on the International Scientific Advisory Council of the Waterloo Institute for Complexity and Innovation, and a member of the External Faculty of the Northwestern Institute on Complex Systems at Northwestern University, as well as a member of the Steering Committee for the International Conference on Computational Social Science.