A key to improving at any task is frequent feedback from people whose opinions we care about: our family, friends, mentors, and the experts. However, such input is not usually available from the right people at the time it is needed most, and attaining a deep understanding of someone else’s perspective requires immense effort. This paper introduces a technological solution. We present a novel method for automatically modeling a person’s attitudes and opinions, and a proactive interface called “What Would They Think?” which offers the just-in-time perspectives of people whose opinions we care about, based on whatever the user happens to be reading or writing. In the application, each person is represented by a “digital persona,” generated from an automated analysis of personal texts (e.g. weblogs and papers written by the person being modeled) using natural language processing and commonsense-based textual-affect sensing. In user studies, participants using our application ...