The purpose of this book is to present information about communicating in terms of "if-then" propositions that are based on scientific study. The book consists of two sections--Communication Behavior and Communication Experiments. The chapters in the first section of this book consider relationships, messages, information diffusion, and achieving change. In this section of the book, some predictive propositions that appear to be supported by existing scientific research are discussed. A sample of supporting research for each proposition is reviewed and at least one representative study is abstracted. The second section outlines twenty basic experiments which students can carry out as a means of learning about scientific research and verifying or refuting some of the predictive propositions discussed in the first section. Step-by-step procedures for conducting these experiments are also provided. (Author/RB)