Six Proven Principles of Persuasion


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Anyone who’s been around internet marketing for a while is familiar with the concepts of “scarcity” and “social proof”.

Here’s an example of these two concepts in action:

“Hey {!firstname_fix},

Frank Kern is launching Mass Control 13.0! Dude, EVERYBODY is buying this product! You better get it quick, because there are only 13 copies left!”

Note the claims that “EVERYBODY is buying this product” (social proof), and “there are only 13 copies left” (scarcity).

What a lot of internet marketers don’t know is that these two tactics come from a classic marketing text by Dr. Robert Cialdini.

Cialdini’s book (Influence: The Psychology of Persuasion) has a lot more good stuff than just those two tactics, so I’ve decided to post a summary of it. I highly recommend you read the book – it’s chock full of awesome examples of psychological principles in action. But in the meantime, check out my summary below.

Summary of Influence: The Psychology of Persuasion

In this book, Dr. Robert Cialdini outlines six “principles of persuasion” that can be used to influence behaviour.

He came up with these principles from a review of academic studies on behaviour, along with his own empirical study over a three year period. During that period, he trained in a variety of sales-oriented industries, such as car sales, fundraising, etc. He observed the behaviour of “compliance professionals” (as he calls them), and combined these observations with the conclusions of academic experiments in psychology.

The six principles of persuasion are:

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

Key Points from the Book

The six principles of persuasion are as follows:

1. Reciprocity

  • Humans are programmed to reciprocate when we are given something. The act of receiving from someone else instils in us the need to repay that favour (however small). There are evolutionary reasons for this (i.e. it supports cooperation).
  • Reciprocation “pressures the recipient of an already-made concession to respond in kind”.

2. Commitment and Consistency

  • Human beings innately want to be seen as consistent. Inconsistency in a human being is considered a fault, and is associated with a host of other negative qualities (e.g. untrustworthiness, instability). As a result, when people commit to an act, belief, attitude, etc. they wish to maintain that stance, in order to be viewed as consistent.
  • Importantly, commitment will only be felt if the recipient of our request accepts “inner responsibility for the actions we want them to take”. In other words, if people feel forced to take an action, they will not “own” that decision, and will not feel sustained commitment.

Several tactics can be used to obtain commitment:

a. Foot-in-the-door technique. Startwith a small request “in order to gain eventual compliance with related larger requests”. Getting people to make small changes to their behaviour will not only put them on a track to larger requests because they want to be seen as consistent, it will do so also because a change in a person’s behaviour also changes their self-image.

b. Written commitment. A written commitment is effective because of the physical act of writing something down.

c. Public commitment. When a person makes a commitment to others, they will want to keep that commitment to ensure that they are viewed as “consistent” by others.

3. Social Proof

  • This principle states that we learn what is correct by finding out what other people think is correct. This can be done through asking, or observing the behaviour of others.

Conditions under which social proof can most strongly affect behaviour include:

a. Situations of extreme uncertainty (i.e. when a person has no idea what is going on)

b. Similarity. Social proof works very powerfully in influencing behaviour when we are “observing the behavior of people just like us”.

4. Liking

  • Put simply, we’re more inclined to respond to a request if we like the person making the request.

Several factors contribute to a person’s likeability:

a. Physical attractiveness. People who are physically attractive also enjoy the “halo effect”, in which people think that because they’re attractive, they are also more intelligent, kind, etc.

b. Similarity. We like people who are similar to ourselves (in dress, age, expressed background and interests, etc.)

c. Familiarity. We like things that are familiar to us.

d. Cooperation. When someone works with you to achieve a shared goal, you like them more.

e. Compliments. People who give compliments are more liked.

f. Association. People who are associated with good/positive people, events, etc. are more likely to be liked (e.g. it’s the “don’t kill the messenger” phenomenon. A weatherman can be disliked simply because he predicts bad weather).

g. Appearance of Truthfulness. A real-life example of this is when bloggers will review a product by first mentioning its faults. They then talk up the benefits of the product (which they claim outweigh the product’s negatives), and end with an endorsement.

h. Primary Interest. This is when someone seems to be arguing against their own best interests in favour of yours (i.e. they’re “on your side”).

5. Authority

  • Human beings have a “deep-seated sense of duty to authority”.
  • Even the appearance of authority is enough to obtain compliance (e.g. an actor wearing a doctor’s lab coat on a commercial)

Symbols that can trigger compliance in the absence of real authority:

a. Titles

b. Clothes

6. Scarcity

  • The psychological underpinning of this principle is that “opportunities seem more valuable to us when their availability is limited”.
  • Related to this, people are more motivated to avoid losing something, than to potentially gain something of equal value. (This ties in with Kahneman’s prospect theory.)
  • When our desire for something scarce grows, we make sense of the desire by assigning it “positive qualities to justify the desire”.

Specific forms of scarcity:

a. Limited number

b. Limited time (i.e. deadline)

c. Competition. Competition increases desire for something (e.g. to goad indecisive buyers, realtors will “invent” another potential buyer)

  • An additional psychological principle is the contrast principle. Contrast affects the way we see things “that are presented one after another. Simply put, if the second item is fairly different from the first, we will tend to see it as more different than it actually is”. Cialdini gives the example of speaking with a beautiful woman at a cocktail party, then speaking with an unattractive one. Because she came second, that woman will seem even more unattractive than if she had been spoken with first.

Cialdini also states that in an increasingly complex world, people are faced with more and more information with which to make decisions. To deal with this amount of information, “when making a decision, we will less frequently enjoy the luxury of a fully-considered analysis of the total situation, but will revert increasingly to a focus on a single, usually reliable feature of it.”

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    • moe says

      Thanks for dropping by, Arm.

      According to Cialdini’s book (“Influence: The Psychology of Persuasion”), these six principles absolutely work in regular social situations – they’re applicable to any situation in which human beings interact.

      Cialdini’s book gives many examples of experiments that were conducted in social settings. If you haven’t read the book yet, I highly recommend it.


  1. says

    Hi Moe,

    Great articles, I have decided to go through them ALL in one day!

    I have read the part on commitment and consistency several times and I do not understand it, can you please give some examples from an Internet Marketers point of view?

    Can you also give an example of competition under scarcity?

    Thank you,


  2. says

    Hi Atif,
    To take advantage of this phenomenon you need to ask for a commitment from your prospect, no matter how small. This is why it is always a good idea to ask your potential customers to show some kind of allegiance to you or your business by making a contribution (e.g. a blog comment) or action (e.g. opt-in), because even a small commitment can lead to a long term relationship.
    For example, if you want to sell a high ticket coaching course and your prospect has refused your initial $1,997 offer, try asking him or her for a small commitment, such as a $1 deposit for a “14 Day Trial” and a monthly subscription of $47 a month thereafter.
    The prospect may feel less intimidated if they only pay $1 and, after the trial period when they need to cancel the program, to avoid cognitive discord, they may justify the expense in their mind and continue with the course.
    The Law of Commitment (Charles A. Kiesler, 1971) proposes that once you make a choice you are under internal, psychological, and external (social) pressure to remain consistent with that commitment.
    From a marketer’s point of view this theory is very interesting because it suggests that if you can make your prospect commit to your offer in any way, no matter how small, then they have psychologically entered your sales funnel.
    Once you commit to something, there is a rule of consistency (The Consistency Principle), that will push you to be consistent with your previous decisions no matter what.
    Richard G. Lewis
    Author of “The 25 Laws of Persuasion”

  3. says

    Thanks Moe, I love this stuff :) All good marketing is based on sound psychology. As for Cialdini’s six principles, I think there are at least 25 to 30 Laws of Persuasion (hence the title of my book). For example, every marketer knows the power of the Law of Curiosity.

    Keep the good stuff coming Moe

  4. Moe says

    Yep, that’s what attracted me to marketing in the first place. I’ve always been interested in behaviour: why we behave how we do, and how that behaviour can be shaped. The ultimate goal of marketing is to influence behaviour.

    Where can people pick up your book?



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