1. Reciprocity
People feel a pull to return what they’ve been given. It’s why the free taster sells the cheese and the free consultation starts the project. The application isn’t "give things away" — it’s give something of real value first. A truly useful guide, an audit finding, honest advice that costs you a sale today: each one creates a quiet debt that customers repay with attention, trust and, eventually, business.
2. Commitment and consistency
Once someone takes a small step, they want their next steps to match it. The customer who ticks "yes, send me the checklist" is measurably closer to buying than the one who did nothing — not because of the checklist, but because they’ve started becoming the kind of person who works with you. Design your funnel as a staircase of small, easy yeses rather than one giant leap.
3. Social proof
When people are unsure, they look at what others did. Reviews, case studies, "as used by", the queue outside the restaurant — all one principle. Its power is exactly why we treat it as sacred on this site: there is no faster way to destroy trust than social proof that turns out to be invented. Show only what’s real, make it checkable, and it works twice as hard.
4. Liking
People buy from people they like — and we like people who are similar to us, who pay us genuine compliments, and who feel familiar. In practice this is the case for sounding like a human being: writing the way your customers speak, showing the faces behind the business, and admitting imperfections. Polished corporate voice reads as a stranger. A recognisable person reads as someone to trust.
5. Authority
Credentials, track record, demonstrated knowledge — signals that you know what you’re doing lower the perceived risk of saying yes. The trick is that demonstrated beats claimed every time. A page explaining precisely how you work persuades more than any "leading provider" boast. (It’s the principle this entire Insights section is built on. Yes, we know.)
6. Scarcity
What’s rare feels valuable, and what’s disappearing feels urgent. It is the most powerful principle on this list and the most abused — the fake countdown, the eternal "only 2 left". Our rule, and the one we’d give you: scarcity may only ever describe reality. A truly limited diary, a price that truly rises next quarter, a cost of waiting that’s real — say them straight. Invented urgency wins the sale and loses the customer, and the exchange rate on that trade is terrible.
The seventh: contrast
Cialdini opens his book with one more lever that frames all the others: nothing is judged alone. £500 feels expensive after £50 and cheap after £5,000. The order in which you present options, prices and problems changes how each one lands — which is why good pricing pages, good proposals and good sales conversations are sequenced, not just written.
The line
Every principle here has an honest version and a manipulative one, and the difference is always the same test: would it still work if the customer knew exactly what you were doing? Real reciprocity survives daylight. Fake scarcity doesn’t. Persuasion built on true things compounds — each sale makes the next one easier. Persuasion built on tricks borrows from future trust at ruinous interest.
In shortTest every persuasive device in your marketing against one question: would it still work if the customer knew exactly what you were doing? Anything that fails is borrowing from future trust.
These principles are the working method behind our copywriting. More about copywriting →