Book review "Influence" by Robert B. Cialdini

Recently, I finished “Influence” by Robert B. Cialdini. I like reading books about Psychology and “Influence” both is comprehensible and useful. In this article, I want to highlight some of the most important take-aways I found to be of relevance to my life.

Contrast Principle

This principle states that while comparing two things with each other, the second thing is perceived to be much more different if it is only fairly different. The example in the book is lifting a slightly heavier object after lifting a light object. The second object is perceived as much heavier than it actually is. This is the reason why good salespersons offer more expensive items first to make the following items appear to be less expensive, even when they actually are.

I think humans use that principle quite often and without knowing it’s name or how it works. An example from estimation meetings in software development teams: It comes naturally to state a significantly higher number for an estimation of a task first, only to then tell the real estimation. That way, a big estimation can be rendered to look relatively small compared to the over-the-top number mentioned first.

Rule for Reciprocation

The rule for reciprocation simply states that humans want to pay back presents, favors or concessions as soon as possible. A kind action like paying for someones drink triggers the wish in paying back the favor by buying a drink for the other person in return. This could be one of the corner stones on which human culture was / is built. Without this mechanism, egoism would have it’s way and cooperation between people would be less likely.

This rule can also be used to get things more easily from other people. Before asking a favor of another person, it’s wise to give a “present” to that person to trigger a wish for pay-back. A less obvious version of the rule can be used in negotiations. To get a specific yearly salary, it’s better to ask for a slightly higher pay rate instead of the targeted amount of money. That way, if the other person denies the exaggerated request, it’s time to ask for the really intended sum. The imaginary difference between the two sums could be seen as a concession which, according to the rule of reciprocation, has to be payed back as soon as possible. “Ask for 120% if you want 100%.”


People want to be seen as consistent in their actions. All their actions should form a logical orchestration in which every act adds to the coherent image of the person. This is the reason why smart people do stupid things: Because they did something that just forces them to do something else to stay consistent. Let’s assume a salesperson convinces a buyer in acquiring an environmental-friendly electricity plan. This plan costs more than the standard tariff, but not by much. If the buyer is offered an electric car which is said to be hugely environmental-friendly, chances are that the buyer also think about embracing that offer. It’s just consistent for someone who just commit to an ecological electricity plan.

The rule for consistency can be used to manipulate people, too. The simple question “How are you today?”, followed by a pause to let the counterpart answer, will most likely put that person in a good mood because humans tend to answer this question with a positive attitude: “I’m fine, thank you.” If now asked to give money to the poor or some other altruistic cause, there’s only one action to stay consistent: Because the person just admitted that everything is fine which is equals to the absense of problems, there’s no reason to not give money to charity. Furthermore, more elaborate plans can change the perceived self-imange of a person in a way that this person will act very differently. There are great examples for this in the book.

A particular interesting “usage” of this principle is to write down ones goals and telling as much people about them as possible. By taking the time and expressing plans with written words, a certain commitment is given. By additionally telling others about those plans, social pressure is applied. If the goals were not to be reached for some reason, not only would others be aware of the inconsistency, but the person itself would be inconsistent with itself. Hence, writing down goals and plans is a great tool to enhance the likelyhood for success.

Other Interesting Concepts

The book contains many other interesting concepts like the social proof. The concept of social proof is also deeply rooted in the history of mankind and the fast-thinking psychology of each of us. In short: “If everyone is doing it, it must be the right thing.” This concept is the reason why everyone is changing lanes on the highway without any hint of problem in the current lane. It’s also the reason why there is a raise in the suicide rate after celebrities ended their life with much press attention (Werther effect).

The concept of “liking” states that persons who are like each other are trusted more. That is the reason why salesman try to be as much like their customers. Or, the other way around: It’s the reason for war and hate. Being like someone means that there are people who are unlike other people - the definition of groups. And groups mean differences to other groups which causes conflict. This conflict can only be bridged by joint efforts towards a common goal.

Another interesting concept is the “luncheon technique” that describes that people who are fed are more accessible and fond of other people. This applies to other “things” as well like models and presents.


“Influence” is one of the best books about psychology I read, I highly recommend it.