How to win people over

How to win people over using the six principles of persuasion

Dale Carnegie’s seminal self-help book How To Win Friends And Influence People celebrated its 80th anniversary with the sale of its 15 millionth copy. The need to influence business associates is as relevant today as it was in 1936. But can successful persuasion really be defined by the application of a handful of scientific principles?

Yes, says influencing expert Professor Robert Cialdini, who’s made a career of studying what factors must be employed in order for someone to say ‘yes’ to your request. 

“It would be nice to think that people consider all of the available information in order to guide their thinking, but the reality is often different,” says Cialdini. “[There are] six scientifically-validated principles of persuasion that provide for small, practical, often costless changes that can lead to big differences in your ability to influence and persuade others in an entirely ethical way.”


1. Reciprocity

Tips increase on average by 3% when the waiter brings a small gift like a mint or fortune cookie along with the bill. Two mints or two fortune cookies don’t just double the tip; they quadruple it. Most tellingly of all, waiters who bring one mint, walk away before pausing and returning with a second mint and a comment about valuing his customers, see his tips rise by 23%. 

“People are obliged to give back to others the form of behaviour, gift or service that they have received first. If a colleague does you a favour, you owe that colleague a favour. People are more likely to say “yes” to people they owe,” says Cialdini. “The key...is to be the first to give and ensure what you give is personalised and unexpected.”


2. Scarcity

When British Airways halved the number of daily London to New York Concorde flights, ticket sales went through the roof. Nothing had changed about the service, price or the aircraft – people simply wanted more of the resource when it became scarcer.

“The science is clear,” says Cialdini. “It’s not enough simply to tell people about the benefits they’ll gain if they choose your products and services; you’ll also need to point out what is unique about your proposition and what they stand to lose if they fail to consider your proposal.”


3. Authority

Patients are much more likely to follow the exercise regimes of their physiotherapists when their medical credentials are displayed on the walls of their consulting rooms. And people are much more likely to give change for a parking metre to a complete stranger wearing a uniform, than one wearing everyday clothes. 

“It’s important to signal to others what makes you a credible, knowledgeable authority before you make your influence attempt,” says Cialdini. But he acknowledges the challenge therein: “You can hardly go around telling potential customers how brilliant you are, but you can certainly arrange for someone to do it for you.”

Real estate agents increased their appointments by 20% when they instructed their receptionists to introduce them to new customers with a comment about their credentials: “Lettings? Let me connect you with Sandra who has 15 years experience letting properties in this area. I’ll put you through now…”


4. Consistency

Residents in a neighbourhood were asked if they’d take part in trying to reduce the speed of traffic by displaying large wooden boards on their front lawns. Unsurprisingly, many declined. In a nearby neighbourhood, residents were first asked if they’d display a small postcard in their front windows. This saw a 400% increase in the number of people who, 10 days later, were willing to erect the wooden board. 

The key lesson is that starting out with a small request is more likely to lead to compliance with a much larger demand. 


5. Liking

MBA students were asked to take part in negotiations using the principle that ‘time is money’ and they had to come to an agreement as quickly as possible. Another group of students were able to reach a deal typically worth 18% more to both parties when they first spent time sharing personal information and identifying a similarity they shared. 

The bottom line: investing time in getting to know your colleagues, and finding common ground, is likely to lead to more favourable deals. 


6. Consensus

If you want to convince someone that they should buy into your idea or service, demonstrate the tangible benefits being enjoyed by those who already have.

Hotels typically try to encourage towel reuse by drawing guests’ attention to the environmental advantages. But towel reuse increases by 33% when the cards left in bathrooms instead draw attention to the number of other guests who are already reusing their towels. “[It’s an effective strategy to] point to what others are already doing, especially many, similar others,” says Cialdini. 

Watch Professor Cialdini’s principles brought to life in the following animation.