This book addressed how usability improvement and motivational design affect learners' motivation and learning performance in a self-paced, online learning environment. The author also investigated the interrelationships between commonly-used usability measures and the motivation measures based on Keller's ARCS model. Results suggested a significant interface design effect on learner motivation. Small to medium positive correlations were found between usability satisfaction and three motivation measures, i.e., attention, relevance and satisfaction.