BSc in Physics, University of New South Wales; PhD in Theoretical and Applied Mechanics, Cornell University. Principal Research Scientist, Yahoo Research, directs Human Social Dynamics group. External Faculty Member, Santa Fe Institute and Nuffield College, Oxford. Research on social networks and collective dynamics appeared in journals including Nature, Science, Physical Review Letters and American Journal of Sociology. Author: Six Degrees: The Science of a Connected Age (2003); Small Worlds: The Dynamics of Networks between Order and Randomness (1999).