Robert Cialdini was a social psychologist who suspected he was being manipulated all the time and didn't know how. So he spent three years undercover as a salesperson — at car dealerships, fundraising offices, ad agencies, telemarketing firms — taking notes. He emerged in 1984 with a book called Influence, identifying six near-universal levers of compliance.

Reciprocity. People feel obliged to return favors, even unwanted ones. The reason free samples work is not that you taste the cheese. It's that you take a piece of the salesperson's effort. Hare Krishnas in airports gave away flowers — knowing the receiver would awkwardly donate to be free of the obligation.

Commitment and consistency. Once you say something out loud, you'll twist yourself in knots to be consistent with it. Door-to-door salespeople ask leading questions ('You're a generous person, right?') so that later refusal feels self-contradictory.

Social proof. We follow what others are doing. Laugh tracks were invented because people genuinely laugh more when they hear others laughing. Empty restaurants stay empty.

Authority. We comply with perceived experts. White coats on TV doctors selling toothpaste. Diploma frames on dentist walls. Job titles on email signatures.

Liking. We say yes to people we like. Tupperware parties leveraged this — the customer was buying from a friend, not a stranger. Saying someone's name often makes them like you more.

Scarcity. Limited supply, time-limited offers, 'only one left' signs all hijack the same instinct.

Once you know the six, you cannot stop seeing them. Every billboard. Every restaurant. Every meeting you've ever been in. The architecture of persuasion is not subtle once you have the blueprint.