Influence: The Psychology of Persuasion by Robert B. Cialdini first appeared in 1984. The book was released again in 1994 and 2007. The first three editions of Influence, which has been translated into 44 languages, tallied 5,000,000 sales around the world. In 2021, Cialdini released the fourth edition of the book. The latest version includes current insights into the digital age and many testimonials from readers of previous editions.

In Influence, Cialdini describes “levers of influence,” specific methods that can be utilized to achieve compliance, that is, to persuade a person to say “yes” to a request. Earlier versions of Influence detailed six levers of influence. In the 2021 edition, however, the author adds a seventh lever. Cialdini is Psychology and Marketing Professor Emeritus at Arizona State University and the author or co-author of several related titles. He has received many awards, is a member of the National Academy of Sciences, and was elected President of the Society of Personality and Social Psychology.

This guide uses the 2021 hardcover edition from Harper Business.

Content Warning: Chapter 4 contains a discussion of the People’s Temple mass suicide, in which over 900 people lost their lives. Chapter 8 contains a description of the summary execution of several prisoners in a World War II Nazi concentration camp. There is also a brief discussion of hazing rituals.

Plot Summary

In Chapter 1, “Levers of Influence,” Cialdini explains that “levers of influence” refers to seven different sets of actions that a persuader—often referred to as a “compliance professional”—may use to persuade individuals to say “yes” to a persuader’s request. These levers are all reflective of shortcuts that individuals may use to make quick decisions about significant issues.

The author discusses “fixed action patterns.” These are animal behaviors that are cued by specific circumstances. Just as animals have fixed action patterns, so humans have similar rote behaviors. Cialdini expresses the idea that these human behaviors, which he calls “shortcuts,” emerged among human ancestors as survival tactics because they allowed people to make quick decisions in the face of complexity. He notes that today’s world is likewise extremely complex and humans still need shortcuts.

Cialdini discusses “profiteers,” individuals who understand how human decision shortcuts can be manipulated to their advantage. Cialdini says he will discuss the seven levers of influence, demonstrating how someone can manipulate a person into compliance—saying “yes”—with no apparent effort.

In Chapter 2, “Reciprocation,” the author focuses on the phenomenon of extending generosity to someone and expecting that person to respond in kind, typically with even greater generosity. This tendency to return a favor for a favor is a favorite tool of compliance professionals, who use it to elicit great returns for small expressions of generosity. This tool is frequently used by politicians. Cialdini points out that the Cuban Missile Crisis was quietly solved through reciprocation when President Kennedy offered to take nuclear missiles out of Europe if the Russians would remove theirs from Cuba.

Persuaders, who give something to individuals unasked, engender within those individuals a feeling of debt. They respond by giving something more significant to their apparent benefactors. Cialdini lists several subtle, highly effective methods used by compliance professionals to achieve their aims through reciprocity.

In Chapter 3, “Liking,” the author notes that people are quite likely to say “yes” to those they like. This is the idea behind the Tupperware Party, to which a homemaker invites friends. Several factors contribute to a person being likable. These include physical attractiveness, shared similarities, and the use of compliments.

Constant exposure to someone creates an air of acceptance, making it easier to like that person. However, if one is a continual harbinger of negativity—for instance, a weather forecaster or news reporter—people impute their hostility to the messenger. Using this principle, compliance professionals use attractive spokespersons to create a lasting impression.

Chapter 4, “Social Proof,” deals with the tautological notion that popularity causes things to be popular. Compliance professionals recognize that advertising something as the most popular or bestselling further increases the popularity of the most popular items. Unscrupulous profiteers attempt to use this principle by feigning the popularity of an item. Cialdini says social proof works most effectively when there are three elements present: uncertainty (not knowing the best choice), a mass of people making the same decision, and similarity between the confused person and the mass of people.

The author notes that there is a decidedly dark side to this principle. Not only can one follow the crowd only to find they are going in the wrong direction, but one can also make irrevocably bad decisions by following the example of others. He describes the way deaths by suicide beget copycat suicides and, likewise, so do homicides. Perhaps the worst example of this was the People’s Temple mass suicide, in which 909 individuals willingly followed the lead of Jim Jones and drank poison.

Chapter 5, titled “Authority,” deals with reliance upon the guidance of an individual who is high-ranking, wise, or knowledgeable to dispense needed information. After describing the merits of a society in which there are layers of authority, Cialdini describes the dangers of unchecked authority—specifically noting that there is no higher authority watching over the actions of medical doctors—as well as unwavering trust in the correctness of authorities.

In addition to the issue of unchecked actual authority, Cialdini notes that this lever of influence is particularly susceptible to con artists who understand how to appear to possess authority. He lists three elements that suggest one has authority—a title, good clothing, and elegant trappings—all of which can be faked. Real authority figures, he notes, exude expertise in a particular field and trustworthiness. The best way to determine whether someone is an actual authority is to know what data they should possess. Also, true authority figures know the limits of their authority and tend not to exceed them. Thus, celebrities endorsing products are not actual authorities.

Chapter 6, “Scarcity,” concerns the principle of scarcity. It states that resources that are scarce are viewed as being more valuable. The flip side of the scarcity principle is that people invariably strive to hang on to what they have rather than risking what they possess. Cialdini calls this “loss aversion.” The author notes there are many ways compliance professionals use the principles of scarcity to boost interest in certain items. The less available something is, the more valuable it appears to be.

Cialdini spends much of the chapter discussing how the scarcity principle is at work in situations where citizens lose things, particularly rights and freedoms. He discusses the censorship of books, restrictive local laws, the Civil Rights Movement, and the attempted overthrow of Russian President Mikhail Gorbachev as examples of citizens spontaneously reacting against governments who try to take away once-possessed freedoms.

The title of Chapter 7 is “Commitment and Consistency.” This refers to a lever of influence centered around an individual’s consistency in fulfilling a commitment they have made, even if they decide the decision is not in their best interest. The human propensity to be consistent is reinforced by parental teaching, by the individual’s desire to be perceived as consistent, and by the fact that consistency means never having to rethink one’s decisions. The lever of consistency can be used against someone by getting them to make a verbal or written commitment and reminding them of the importance of being “as good as their word.” Once an individual has made a commitment, persuaders can use it to impact the person’s self-image.

Chapter 8, “Unity,” deals with the seventh, most recently added lever of influence. Cialdini describes the basic human reality that all people see themselves as belonging to certain groups that exclude non-members. The author follows the various delineations that may be included in one’s group: family, locality, religion, nationality, political party, and religious affiliation. Preference is always given to those who are in the “we” group.

Cialdini describes how compliance professionals use group familiarity to achieve compliance. He explains as well how social scientists have learned to build cohesiveness and to open traditional groups to include outsiders. The author expresses hope that these tools can help people recognize that humanity itself is actually one great “we” group.

In Chapter 9, “Instant Influence for an Automatic Age,” Cialdini discusses the unrelenting, overwhelming wave of daily information people currently experience. While information is abundant, knowledge is not, he argues. It is not possible for an individual to synthesize all the available data to make completely informed decisions. Thus, he argues, it is necessary that people continue to use the seven basic decision-making shortcuts as they negotiate contemporary life. Knowing how these shortcuts work—as well as how some try to corrupt them—is the best defense for retaining the ability to make quick, accurate decisions.