Written for teachers, trainers, and instructional designers -- anyone who is responsible for designing or preparing instruction -- this book begins with one basic premise: individual differences mediate learning at all levels and in all situations. That is, some learners find it easier or more difficult to learn some skills or to learn from certain forms of instruction because they vary in terms of aptitude, cognitive styles, personality, or learning styles. This volume describes most of the major differences in a readable and accessible way and demonstrates how to design various forms of instruction and predict the ease with which learners will acquire different skills. Most books that discuss any learner differences focus on those that characterize special education populations, whereas this book focuses on normal learners. Designed as a handbook, this volume is structured to provide easy and consistent access to information and answers, and prescriptions and hypotheses. When definitive answers are not possible because there is no research documentation, the authors suggest theories designed to stimulate future research.