In this article, we describe the usage of persuasion profiles in a large scale, N = 1,129, field trial. Persuasive technologies-technologies intentionally designed to influence user behavior-are emergent and becoming more and more individualized and ubiquitous. Individual differences in people's responses to often used persuasion principles-different psychological means by which to influence users-motivate personalization. We describe how, through identification, representation, and measurement, persuasive technologies can personalize their persuasive attempts. Next, we show that dynamically adapting a persuasive technology to the responses of its users increases the effectiveness of the system. Ubiquitous computing systems are, because of ...