Noting that recent research and theory from the expanding field of psychobiology have not been integrated into the study of human communication, this paper offers a synthesis of principles from several leading psychobiological scientists as a step toward a possible unifying approach to communication philosophy, theory, and research. The paper argues that psychobiology is particularly useful for understanding the motives for message selection and other communication behaviors, and illustrates this usefulness by applying psychobiological principles to a particular research question: Why are normally rational humans attracted to negative messages of various types? The paper then discusses the possible threat to traditional humanistic, philosophical, and behavioral thinking posed by psychobiological assumptions and the limitations of psychobiology. Also provided are an inventory of psychobiological principles and some original communication hypotheses derived from them. (Author/FL)