Robert B. Cialdini is an American psychologist, professor, and writer, well known for his work on the psychology of persuasion and compliance. He was born on April 27, 1945. Cialdini is best known for his 1984 book, "Influence: The Psychology of Persuasion," where he introduces six principles of influence: reciprocation, commitment and consistency, social proof, authority, liking, and scarcity. His research has had a significant impact on the fields of business, marketing, and psychology. Cialdini's work is often used by sales and marketing professionals to develop strategies for more effective persuasion. He is also a frequent lecturer and consultant in the areas of persuasion, compliance, and negotiation.