Robert Cialdini

Reciprocity

We feel obligated to return favors. Give first — a sample, a concession, genuine help — and people feel a pull to give back. The most powerful of the principles, and the easiest to trigger.

Commitment & consistency

Once we commit to something — especially out loud or in writing — we feel pressure to act consistently with it. Small initial commitments make larger, aligned ones far more likely.

Social proof

When unsure, we look to what others (especially similar others) are doing. 'Most people choose X' is one of the strongest nudges there is — which is why testimonials and 'bestseller' labels work.

Authority

We defer to credible experts and symbols of authority (titles, uniforms, credentials). Signaling genuine, relevant expertise — even admitting a small weakness first — sharply increases persuasion.

Liking

We say yes to people we like — and we like those who are similar to us, who compliment us, and who cooperate with us toward shared goals. Rapport isn't fluff; it's a lever.

Scarcity

We want more of what is rare or dwindling, and we fear loss more than we value gain. Genuine scarcity and exclusivity raise desire (fake scarcity is the unethical abuse of this principle).

Unity (the 7th principle)

Added in the 2021 edition: shared identity — 'one of us.' Persuasion is strongest when it comes from inside a group the person belongs to (family, region, team), not just someone they happen to like.

Pre-suasion

From Pre-Suasion: what you do BEFORE delivering a message — directing attention to a 'privileged moment' or idea — can make people receptive before they hear the message itself. Timing and framing the run-up matter as much as the pitch.

The myth: Influence is a how-to manual for manipulating people.

What is true: Cialdini explicitly frames it as a defense as much as a toolkit — much of the book is about spotting and resisting 'exploiters' who weaponize these principles, and he warns that abusing them (e.g. fake scarcity, fake social proof) backfires and is unethical.

The myth: There are six principles of influence.

What is true: There were six in the original; the New & Expanded edition (2021) adds a seventh — Unity (shared identity). If a summary lists only six, it's based on the older edition.

The myth: These are clever 'tricks' that work on gullible people.

What is true: They're deeply wired mental shortcuts that affect virtually everyone, including experts. They exist because they're usually useful heuristics — which is exactly why they can be exploited, and why recognizing them matters.