We propose this book as a celebration of the outstanding research and teaching career of Professor Barbara Coleman Etzel. The editors and authors are her students and her worldwide colleagues. She directed us toward the issues of antecedent control at a time when we thought altering consequences could solve all problems. She developed a model of how a preschool teaching and research laboratory should be run by creating the very environmental controls evident in her work. This book is testimony to her influence on our professional careers and to our affection for her. Analysis of the way the environment influences behavior is essential to our understanding of human development. This volume collects original, never-published work that describes how people conceptualize, think, and behave. Environment and Behavior presents empirical studies that test theoretical assumptions and illustrate how to integrate environmental awareness into professional practice and design. The ability to categorize—to think in larger and more inclusive classifications and, at the same time, in smaller and more exclusive subdivisions—is a hallmark of conceptual development, It is the kind of development that makes humans distinctly rational, symbolic, and logical. This book presents a new way of viewing the conceptual development of normal and developmentally disabled children and the conceptual reorganization of adults. Individual conceptual ability is demonstrated across an impressive range of issues: private events, language development and function, child abuse, sexual abuse, drug abuse, autism, aging, professional practice, and environmental and cultural design. Additional commentary for each section is provided by the editors. Those working or studying in the areas of psychology, education, human development, social work, and disability will find this book to be a current and thorough introduction to the subject.