This book is about communication. We are living in an era when essential communications and services are suspended, interrupted, and disturbed — yet unwanted communications — the junk mail and unsolicited telephone calls — continue to pour into our lives. The focus of this book is on extra-linguistic messages — nonverbal expressions that are part of every communicative/ behavioral event. It is a collection of authors who are seeking to discover the structure of behavior in human communication and interaction with each other and with their environment. The articles treat current research, with one exception. This is a reprint of a 1948 article that pleads for 'the unity of science' — written with the idea that only by means of a cross-disciplinary approach can we draw nearer to an understanding of human behavior.