This series, Children's Language, reflects the conviction that extensive work on entirely new fronts along with a great deal of reinterpretation of old-front data will be necessary before any persuasive and truly orderly account of language development can be assembled. None of the chapters are simply reviews, and none of the volumes are handbooks or reviews or introductory texts. Rather the volumes try to capture the excitement and complexity of thinking and research at the growing, advancing edges of this broad field of children's language. In line with these goals for the Children's Language series the present volume includes coverage of a fairly wide range of topics and subtopics. The authors for each chapter will weave their own story and we leave to them the introduction of their main plots and the major and minor characters in their scientific stories. This is volume 6.