This book presents new research in the field of language acquisition and development. The contributors pay attention to first language development and other language acquisition (second, foreign and additional), and focus on issues directly relevant to both areas of investigation. One of the main aims of the book is to discover how research and practice in first language development can contribute to the teaching and learning of other languages, and vice versa. The book is distinctive in this area in its application of theoretical findings to the development of principles, objectives and procedures for language learning. This practical focus can also be seen in the open-minded approach taken to the interpretation of the evidence presented in the book. Rather than setting out to prove any particular hypothesis, the book aims to develop practical applications relating to the tendencies indicated by the research. Language Acquisition and Development will be of interest to postgraduates and academics researching language acquisition, language development and applied linguistics and to language teachers with an interest in language learning theory.