Influence: The Psychology of Persuasion, Revised Edition by Robert B. Cialdini is a foundational psychology and marketing book that explains the core principles behind why people say “yes” and how persuasion actually works.

Drawing on decades of research into compliance and behavioral psychology, Cialdini identifies six key principles of influence: reciprocity, commitment and consistency, social proof, authority, liking, and scarcity. He shows how these triggers shape everyday decisions in marketing, sales, negotiation, and social interaction, often operating below conscious awareness. Through real-world experiments and case studies, the book illustrates how these psychological shortcuts can be used ethically to guide behavior—or exploited in manipulative ways—making it a practical guide for understanding both persuasion and resistance to it.