This book is designed to help second and foreign language teachers understand how languages are learned. Chapter 1 examines several theories on how young children acquire their first language, including behaviorist, innatist, and interactionist models. Chapter 2 presents and analyzes several theories on second language (SL) learning. Chapter 3 addresses how individual learner characteristics and different contexts for SL learning may affect success. The discussion includes issues such as the importance of learners' attitudes toward the second language and the possibility that there is a special aptitude for language learning. Chapter 4 reviews research findings about SL learners' changing knowledge of the language and their ability to use that knowledge. Chapter 5 focuses on five proposals for the most effective way to teach SLs. Chapter 6 presents 12 popular views about language learning and teaching, critically examining and revising these views in light of current research. (Contains 80 references.) (MDM)