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Influence - Book summary

There are 6 key principles of persuasion which can lead people to say “yes” automatically. Understanding these principles and associated techniques can help you to improve your influence and concurrently guard against others’ manipulation. In this free Influence summary, you’ll learn the 6 principles of persuasion, how they work and how they may be turned into weapons of influence against us.

There are simply too many environmental stimuli for our brains to process everything. Thus, we use specific cues as mental shortcuts to help us react quickly without the need to analyze all the information. For example, a flash of sharp teeth or blade will signify “danger”, causing us to step back instinctively without second thought. With the right cues, we’ll say “yes” automatically without conscious thought.

The 6 Principles of Persuasion

Based on years of research, Cialdini discovered 6 “weapons of influence”, each built on a psychological principle of persuasion. Each principle can be used to bring positive change or deceive others, depending on the intention of the user. Being aware of these weapons allow us to guard against “compliance professionals” (e.g. salespeople or marketers) who specialize in getting people to comply with their requests.

Influence The Psychology of Persuasion summary_6 Principles of Persuasion


When someone does something for us or gives us something, we feel obliged to repay in kind. The Reciprocity Principle is a vital part of human society—it facilitates sharing and cooperation which supports mankind’s social advancement.

  • This applies to gifts, favors, or even perceived concessions. That’s why free samples and small gifts are so effective in soliciting sales and donations. To extract concessions, it’s common for people to use the “reject-then-retreat” and “large-then-small” tactics. Basically, the other party starts with a larger request (e.g. present an item for $20). If you reject the request, he/she makes a smaller request (e.g. present a less valuable item for $5). In this case, you’re likely to agree the 2nd request because (a) the requesting party seems to have made a concession, which triggers you to give a concession by switching from “no” to “yes” and (b) by perceptual contrast, the 2nd request seems smaller.
  • The Reciprocity Principle may be used to push us into uninvited debts or unfair exchanges, e.g. being “forced” to accept an uninvited gift (and later cornered for a sale/donation), or being  small gift or favor may be used to trigger a much larger favor or purchase in return.
  • Learn to identify the true intention of the requester. If the person starts to make demands/requests after giving you a gift or favor, recognize that it’s not a real favor or concession (merely a persuasive manoeuvre) and frees yourself from the sense of obligation and makes it easier to say “no”.

We’ll now take a quick look at the remaining 5 principles. For more details, examples and tips, do get a copy of our complete Influence summary.



Once we take a stand or make a choice, we feel compelled to behave consistently with our earlier commitment and to justify our own decisions. For this principle to kick in, a real commitment must be made, with a fundamental shift in self-image—this is most likely to happen when (a) we’re actively doing something in support of a position or decision, (b) have put in effort into our choice and (c) when our stand is public. Unfortunately, this principle can be used to nudge us toward unfavorable decisions or larger-than-desired commitments. In the full Influence summary, you can learn more about the factors influencing commitment, examples of how this principle is applied around us, and how to avoid being manipulated.

Social Proof

When we’re uncertain how to behave or react, we look to others for answers. We assume that if lots of people are doing something, it must be correct. We find this principle at work everywhere, from long queues to testimonials and phrases like “best-selling products”. This principle is so powerful that it can overcome phobias, cause people to do things they personally disagree with, and even mimic aggression and suicide; it’s the most powerful when we are emulating the behavior of people who are similar to us. Do get our complete Influence summary for more examples of social proof and how to guard against herd instinct, deceitful/erroneous social evidence.


Generally, we’re more likely to agree to someone’s request if we know and like the person. Friendships and personal relationships can have a strong influence on our choices. Even if there’re no established friendships, you can trigger this principle simply by getting someone to like you. We tend to like people who are physically attractive, are similar or familiar to us, are associated with success/good news, praise and cooperate with us. In our full Influence summary, you can learn why referrals and Tupperware parties are so effective, the factors that affect likability, and how you can minimize undesired influences.


We are all conditioned (to varying degrees) to obey figures of authority. However, it’s relatively easy to others to trigger our compliance through symbols of authority like titles, clothing and other status symbols. In our complete summary, we look at how this principle is commonly used and how to protect ourselves against undue influence.


Generally, we perceive something to be more valuable when it’s limited in availability. We value something more if we see its quantity reduced before our eyes (vs if it had been scarce from the onset), and we value it the most if it’s scarce due to demand or competition. Form our full Influence summary, you can learn more about how people react to scarcity (including banned/censored items), common scarcity tactics used to rouse us into buying now, and how to guard yourself against them.

Getting the Most from Influence

Each of these principles offer shortcuts to decision-making, but can also be used against us if we’re not mindful. If you’d like to learn more about how to positively influence others while protecting yourself from deception, do check out our full book summary bundle which includes an infographic, 14-page text summary, and a 29-minute audio summary.

Influence summary - book summary bundle

The book is full of detailed case studies and examples to explain each of the 6 principles, illustrate how and why they work, and how they can be used against us. You can purchase a copy of the book here, or visit for more details.

Read our Pre-suasion summary to learn how to set the groundwork such that people are already more receptive to your messages by the time you present them.

About the Author of Influence

Influence: The Psychology of Persuasion is written by Robert B. Cialdini–the Regents’ Professor Emeritus of Psychology and Marketing at Arizona State University. He was previously a visiting professor at Stanford University, as well as at the University of California at Santa Cruz. Cialdini received his Bachelor of Science degree from the University of Wisconsin, earned his Ph.D. in Social Psychology at the University of North Carolina and received Postgraduate training in Social Psychology at Columbia University.

Click here to download Influence book summary and infographic

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