The First Universal Principle of Influence is Reciprocity: We say Yes To People We Owe

Simply put, people are obliged to give back to others in the form of a behavior, gift, or service that they have received first.

If a friend invites you to their party, there’s an obligation for you to invite them to a future party you are hosting. If a colleague does you a favor, then you owe that colleague a favor. And in the context of a social obligation, people are more likely to say yes to those who they owe.

One of the best demonstrations of the Principle of Reciprocity comes from a series of studies conducted in restaurants. So the last time you visited a restaurant, there’s a good chance that the waiter or waitress will have given you a gift.

Probably about the same time that they bring your bill. A liqueur, perhaps, or a fortune cookie, or perhaps a simple mint.

So here’s the question. Does the giving of a mint have any influence over how much tip you’re going to leave them? Most people will say no. But that mint can make a surprising difference. In the study, giving diners a single mint at the end of their meal typically increased tips by around 3%.

Interestingly, if the gift is doubled and two mints are provided, tips don’t double. They quadruple—a 14% increase in tips. But perhaps most interesting of all is the fact that if the waiter provides one mint, starts to walk away from the table, but pauses, turns back, and says,

“For you nice people, here’s an extra mint,” tips go through the roof. A 23% increase, influenced not by what was given, but how it was given.

So the key to using the Principle of Reciprocity is to be the first to give and to ensure that what you give is personalized and unexpected.

Our Third Principle of Influence is the Principle of Authority: We say YES if a trustworthy expert recommends

This is the idea that people follow the lead of credible, experts.

Physiotherapists, for example, can persuade more of their patients to comply with recommended exercise programs if they display their medical diplomas on the walls of their consulting rooms.

People are more likely to give change for a parking meter to a stranger if that requester wears a uniform rather than casual clothes.

What the science is telling us is that it’s important to signal to others what makes you a credible, knowledgeable authority before you make your influence attempt.

Of course, this can present problems; you can hardly go around telling potential customers how brilliant you are, but you can certainly arrange for someone to do it for you.

Surprisingly, science tells us that it doesn’t seem to matter if the person who introduces you is not only connected to you but also likely to prosper from the introduction.

One group of real estate agents was able to increase both the number of property appraisals and the number of subsequent contracts that they wrote by arranging for reception staff who answered customer inquiries to first mention their colleagues’ credentials and expertise.

So, customers interested in letting a property were told “Lettings? Let me connect you with Sandra, who has over 15 years of experience letting properties in this area.” Customers who wanted more information about selling properties were told “Speak to Peter, our head of sales. He has over 20 years of experience selling properties. I’ll put you through now.”

The impact of this expert introduction led to a 20% rise in the number of appointments and a 15% increase in the number of signed contracts. Not bad for a small change in form from persuasion science that was both ethical and costless to implement.

The Fifth Principle is the Principle of Liking: We Say YES to People We Like

People prefer to say yes to those that they like. But what causes one person to like another?

Persuasion science tells us that there are three important factors. We like people who are similar to us, we like people who pay us compliments, and we like people who cooperate with us toward mutual goals.

As more and more of the interactions that we are having take place online, it might be worth asking whether these factors can be employed effectively in, let’s say, online negotiations.

In a series of negotiation studies carried out between MBA students at two well-known business schools, some groups were told,

“Time is money. Get straight down to business.” In this group, around 55% were able to come to an agreement.

A second group, however, was told, “Before you begin negotiating, exchange some personal information with each other. Identify a similarity you share in common then begin negotiating.”

In this group, 90% of them were able to come to successful and agreeable outcomes that were typically worth 18% more to both parties.

So to harness this powerful principle of liking, be sure to look for areas of similarity that you share with others and genuine compliments you can give before you get down to business.

The Seventh Principle is Unity: We say yes to people who are "of us"

People are inclined to say yes to someone they consider one of them

People feel those inside their “we” groups by a mile.  So, the experience that unity is not about simple similarities. No, the experience of unity is about the identities, shared identities to leverage the principle of Unity and point to commonalities that foster “We” mindsets.

It’s not enough that you and someone else are both left-handed and blonde. Instead, you both have to have a core value that is central to both of your identities.

I'd like to share a powerful example from World War II. In

concentration camps, when one prisoner committed an offense, all prisoners would be lined up, and the tenth prisoner would be executed.

There was a brutal guard who would step behind the line and count, "1, 2, 3, 10, bang." However, in one instance, as he reached the tenth person, he stopped and then shot the eleventh person instead. When questioned by another guard about why he didn't shoot the tenth prisoner, he replied,

"I recognized that man. We grew up together in the same neighborhood." This illustrates the power of unity at work, where a sense of belonging and shared background leads to a compassionate decision, even by a brutal individual.