Information Dynamics Laboratory, Hewlett–Packard Laboratories, Palo Alto, CA 94304

Edited by Harry L. Swinney, University of Texas, Austin, TX, and approved September 14, 2007 (received for review May 25, 2007)

The subject of collective attention is central to an information age where millions of people are inundated with daily messages. It is thus of interest to understand how attention to novel items propagates and eventually fades among large populations. We have analyzed the dynamics of collective attention among 1 million users of an interactive web site, digg.com, devoted to thousands of novel news stories. The observations can be described by a dynamical model characterized by a single novelty factor. Our measurements indicate that novelty within groups decays with a stretched-exponential law, suggesting the existence of a natural time scale over which attention fades.