Colloquium: David Liben-Nowell, Assistant Professor of Computer Science

(Carleton College)

Title: “Tracing Global-Scale Information Flow Using Internet Chain-Letter Data” Although the continuous circulation of information, news, jokes, and opinions is ubiquitous in the worldwide social network, the actual mechanics of how any single piece of information spreads on a global scale have been a mystery. In this talk, I will discuss tracing such information-spreading processes via the reconstruction of the propagation of two recent massively circulated Internet chain letters, one protesting the beginning of the Iraq war and one protesting budget cuts for public radio. The propagation of these letters does not fan out rapidly in the style of a small-world epidemic, but rather produces a narrow but very deep tree-like pattern. This observation suggests a new and more complex picture for the spread of information through a social network, and I will present a probabilistic model based on network clustering and asynchronous response times that produces trees with this characteristic structure on social-network data.