From Robert B. Cialdini's book, Influence, which explores the psychological principles underlying persuasion and compliance, particularly as used by professionals like salespeople and marketers. The book outlines and discusses several core levers of influence, including reciprocation, which creates a sense of obligation to return favors; liking, where people are more easily persuaded by those they favor or are similar to; social proof, which motivates people to follow the actions of others, especially when uncertain; authority, demonstrating that people often blindly obey perceived experts or symbols of power; and scarcity, highlighting that opportunities are valued more when they are limited or threatened with loss. Additionally, the book introduces the principles of commitment and consistency and unity (or "we"-ness), which drive behavior toward alignment with previous actions or group identity, and warn against the dangers of relying on automatic, shortcut responses in an information-rich world.