What is the best way to succeed in persuading your listeners? There is no one “correct” answer, but many experts have studied persuasion and observed what works and what doesn’t. Social psychologist Robert CialdiniCialdini, R. (1993). Influence. New York, NY: Quill. offers us six principles of persuasion that are powerful and effective:

1. Reciprocity
2. Scarcity
3. Authority
4. Commitment and consistency
5. Consensus
6. Liking

You will find these principles both universal and adaptable to a myriad of contexts and environments. Recognizing when each principle is in operation will allow you to leverage the inherent social norms and expectations to your advantage, and enhance your sales position.

Principle of Reciprocity

Reciprocity is the mutual expectation for exchange of value or service. In all cultures, when one person gives something, the receiver is expected to reciprocate, even if only by saying “thank you.” There is a moment when the giver has power and influence over the receiver, and if the exchange is dismissed as irrelevant by the giver the moment is lost. In business this principle has several applications. If you are in customer service and go out of your way to meet the customer’s need, you are appealing to the principle of reciprocity with the knowledge that all humans perceive the need to reciprocate—in this case, by increasing the likelihood of making a purchase from you because you were especially helpful. Reciprocity builds trust and the relationship develops, reinforcing everything from personal to brand loyalty. By taking the lead and giving, you build in a moment where people will feel compelled from social norms and customs to give back.

Principle of Scarcity

You want what you can’t have, and it’s universal. People are naturally attracted to the exclusive, the rare, the unusual, and the unique. If they are convinced that they need to act now or it will disappear, they are motivated to action. Scarcity is the perception of inadequate supply or a limited resource. For a sales representative, scarcity may be a key selling point—the particular car, or theater tickets, or pair of shoes you are considering may be sold to someone else if you delay making a decision. By reminding customers not only of what they stand to gain but also of what they stand to lose, the representative increases the chances that the customer will make the shift from contemplation to action and decide to close the sale.

Principle of Authority

Trust is central to the purchase decision. Whom does a customer turn to? A salesperson may be part of the process, but an endorsement by an authority holds credibility that no one with a vested interest can ever attain. Knowledge of a product, field, trends in the field, and even research can make a salesperson more effective by the appeal to the principle of authority. It may seem like extra work to educate your customers, but you need to reveal your expertise to gain credibility. We can borrow a measure of credibility by relating what experts have indicated about a product, service, market, or trend, and our awareness of competing viewpoints allows us insight that is valuable to the customer. Reading the manual of a product is not sufficient to gain expertise—you have to do extra homework. The principal of authority involves referencing experts and expertise.

Principle of Commitment and Consistency

Oral communication can be slippery in memory. What we said at one moment or another, unless recorded, can be hard to recall. Even a handshake, once the symbol of agreement across almost every culture, has lost some of its symbolic meaning and social regard. In many cultures, the written word holds special meaning. If we write it down, or if we sign something, we are more likely to follow through. By extension, even if the customer won’t be writing anything down, if you do so in front of them, it can appeal to the principle of commitment and consistency and bring the social norm of honoring one’s word to bear at the moment of purchase.

Principle of Consensus

Testimonials, or first person reports on experience with a product or service, can be highly persuasive. People often look to each other when making a purchase decision, and the herd mentality is a powerful force across humanity: if “everybody else” thinks this product is great, it must be great. We often choose the path of the herd, particularly when we lack adequate information. Leverage testimonials from clients to attract more clients by making them part of your team. The principle of consensus involves the tendency of the individual to follow the lead of the group or peers.

Principle of Liking

Safety is the twin of trust as a foundation element for effective communication. If we feel safe, we are more likely to interact and communicate. We tend to be attracted to people who communicate to us that they like us, and who make us feel good about ourselves. Given a choice, these are the people with whom we are likely to associate. Physical attractiveness has long been known to be persuasive, but similarity is also quite effective. We are drawn to people who are like us, or who we perceive ourselves to be, and often make those judgments based on external characteristics like dress, age, sex, race, ethnicity, and perceptions of socioeconomic status. The principle of liking involves the perception of safety and belonging in communication.