This book is aimed at providing the reader (teachers, students and full-time researchers) with a reasonably up-to-date survey and analysis of second language learning theory without covering all aspects of the field exhaustively. This book focuses on that part of the literature that has tried to guide the psychological analysis of the learner language in general and attempts to demonstrate the development of ideas in the subject and give an idea of the state of things in the nineties. This book is divided into three parts. To see how different perspectives on acquisition and performance have been expressed by different models and different metaphors, a historical analysis of research carried out in various parts of the world in the seventies and eighties is provided. This is a precursor to later chapters which comprise an account of the most recent trends and various implications are drawn both for future second language research itself and for people wishing to apply this research to other areas of activity. An interim section (the second part) comprises a discussion of theoretical problems arising from early approaches and touches on a number of alternative approaches that were tried. This book also provides some study questions and activities as well as practical guidelines on the use of available research resources. It should also provide useful information for students in other related disciplines such as bilingualism, first language acquisition, and various branches of applied linguistics. Various research frameworks are dealt with. Such studies are employed here as examples of attempts to treat second language learning in a truly scientific fashion. The topics discussed include the role of mother tongue influence, the contribution of conscious processes in learning, and the differences and similarities between second or foreign learner language and child language development.