This book is an inquiry-based, self-teaching guide that introduces readers to the basic concepts of Signal Detection Theory (SDT) without requiring an extensive background in statistics or advanced mathematics. This is accomplished by posing questions that allow readers to derive the rationale and basic SDT procedures as they work through the program. The reader is seldom “told” a rule. Rules emerge from the questioning strategy employed throughout the program. Readers, in effect, construct a basic understanding of SDT for themselves. The book’s purpose is to expose readers to the important role played by both stimulus salience and behavioral consequences in decision making in ambiguous situations.