vii Drugs and sex are two topics about which most people have strong opinions and weak understanding. Knowledge of each can be gained in many ways, all with associated rewards and risks. Like all textbooks, this one was written in the belief that reading can foster learning. The book is intended to introduce principles of behavioral pharmacology to readers with little or no knowledge of the discipline but with an interest in how drugs affect human behavior. Gleaning anything of value from the text requires two things from the reader. The first is a willingness to accept an analysis of drug effects that shares little with folklore or common sense no­ tions of drug action. The second is a willingness to accept the fact that the behavioral effects of drugs are complex and depend upon a sizable number of pharmacological and behavioral variables. Unless one is aware of these factors and how they determine a drug's actions, the behavioral effects of drugs can be neither pre­ dicted nor meaningfully explained. If it does nothing else, this volume will make it obvious that the behavioral effects of drugs are lawful and can be predicted and understood on the basis of well-established relations between empirical phenomena. De­ scribing these relations and exploring how they allow behavioral ix x PREFACE pharmacologists to make sense of drug effects that are otherwise incomprehensible was a major goal in preparing the text.