Book excerpt: There are hundreds, if not thousands, of substances that are used to modify behavior. While different classes of substances have known effects, one has only to see a group of people drinking to excess to recognize that not everyone responds in the same way to a given substance. Why do substances have the behavioral effects they do, and why do individuals vary in their responses to them? This book provides a conceptual framework for answering such questions. Introduction to Behavioral Pharmacology includes a short overview of behavioral analysis and general pharmacology, followed by detailed discussion of assessment of drug effects, the stimulus properties of drugs, drug abuse, and more.