tions of why such large individual differences in emotions occur. Various authors have offered anthropological, biochemical, ethological, neurological, psycholog­ ical, and sociological models of human emotions. Indeed, the sheer number of competing theories precludes a comprehensive review in a single volume. Ac­ cordingly, only a representative sample of models are discussed in this book, and many equally important theories have been omitted. These omissions were not intended to prejudice the reader in favor of any particular conceptual frame­ work. Rather, this selective coverage was intended to focus attention upon the empirical findings that contemporary theories attempt to explain.