Part 2 of a Series on Persuasion
Social-influence scholars have developed a variety of ways of categorizing the mechanisms through which people persuade others to change their behavior. Robert B. Cialdini's Influence: Science and Practice is one such resource. In the book, Cialdini presents a number of principles of persuasion, citing and discussing a range of research and anecdotes. While most of his examples are drawn from the marketing field, the principles themselves apply much more broadly. They offer insight into ways in which we persuade people to do things. For example:
- In all cultures, people tend to return favors. Cialdini refers to this as the "law of reciprocity," and, for the most part, this form of influence belongs in the essay on exchange power. One of Cialdini's examples, however, deserves mention here. He recounts the story of a German soldier who was very adept at crossing battle lines during World War I, and returning back to his superiors with an Allied soldier for questioning. On one such trip, the soldier he accosted was in the middle of eating a meal and offered his would-be captor a piece of bread. "So affected was the German by this gift that he could not complete his mission. He turned from his benefactor and recrossed no-man's-land empty-handed to face the wrath of his superiors." 
- People tend to behave in ways that they feel they are expected to behave. The wise negotiator can use this to her or his advantage. Cialdini notes Anwar Sadat's mastery of this technique:
Before international negotiations began, Sadat would assure his bargaining opponents that they and the citizens of their country were widely known for their cooperativeness and fairness. With this kind of flattery, he not only created positive feelings, he also connected his opponents' identities to a course of action that served his goals. 
- Social proof, as manifested in the behavior of others, is likely to have an immediate and telling effect on the behavior of observers. Examples of the "monkey see, monkey do" principle abound, whether one is talking about action (e.g., copycat crimes) or inaction (e.g., the failure of 38 onlookers who had many chances to go help Kitty Genovese when she was mugged and killed on a New York street in 1964).
- People are more likely to be influenced by those they like than those they do not. Several factors are associated with liking: physical attractiveness, similarity, praise, familiarity (particularly through mutual and successful cooperation in the past), and association with positive things. This suggests that it is problematic for deep-rooted enemies to persuade each other. Two sides in a protracted conflict have likely emphasized their differences, cast aspersions on each other, avoided contact when possible, and been associated with causing pain and suffering to each other's group for years, decades, or even centuries. They are missing all the factors that lead to liking except, perhaps, physical attractiveness. This may be one of many reasons that third-party intervention is often more profitable than direct negotiation between sworn adversaries.
- People are more likely to respond to the directives of a recognized authority figure, or to be influenced by the testimony of one with authority, than by someone who is not perceived to have authority. Advertisers use this tendency on a regular basis, arranging for well-known and respected people to endorse their products. For example, on the world stage, Jimmy Carter lends his good name to election-monitoring efforts of contested elections, and Desmond Tutu speaks against human-rights violations on behalf of oppressed groups. Such personages can also be particularly effective mediators, as Oscar Arias proved in Central America.
- Finally, scarcity can be a compelling factor in getting someone to do something that she or he otherwise would not do. It is easy to see this in sales pitches in the form of "last chance" or "one of a kind" strategies. "According to the scarcity principle, people assign more value to opportunities when they are less available." As with the "norm of reciprocity," we are probably most likely to see this principle in operation when exchange power is at the fore.
 Cialdini, Robert B. Influence: Science and Practice. 4th Ed. Boston: Allyn & Bacon, 2001, p. 30. New edition (2009), http://books.google.com/books?id=5dfv0HJ1TEoC.
 Cialdini, p. 70.
 Cialdini, p. 231.
By Máire Dugan