Preface -- On The Problem of Predicting Real World Characteristics from Virtual Worlds -- The Use of Social Science Methods to Predict Player Characteristics from Avatar Observations -- Analyzing Effects of Public Communication onto Player Behavior in Massively Multiplayer Online Games -- Identifying User Demographic Traits through Virtual-World Language Use -- Predicting MMO Player Gender from In-Game Attributes using Machine Learning Models -- Predicting Links in Human Contact Networks using Online Social Proximity -- Identifying a Typology of Players Based on Longitudinal Game Data.