Homework Notes

1. Reciprocity vs. Exchange

Cialdini describes Reciprocity as the rule that “people repay in kind.” When someone gives us something—whether a favor, gift, or concession—we feel obligated to return the favor. He notes that this rule is so powerful that even uninvited favors can create a sense of indebtedness. For example, when someone makes a concession during negotiation, the other party is likely to respond with a concession of their own.
The influence tactic of Exchange, by contrast, is a deliberate agreement where both sides trade benefits openly (“you do this for me, I’ll do this for you”). Reciprocity, as Cialdini writes, is less about explicit bargaining and more about the social norm that naturally encourages cooperation.

2. Consistency/Commitment and Cognitive Dissonance

Cialdini explains that once people commit to an idea or course of action, they have both internal and external pressures to behave consistently with that commitment. He writes that “people align with their clear commitments” and that this tendency is especially strong when the commitment is made actively, publicly, and voluntarily.
This works because inconsistency makes people uncomfortable—it challenges their self-image. By sticking with their prior commitments, they reduce that internal tension. As Cialdini puts it, “People want to be consistent with what they have previously said or done.”

3. Authority – Titles, Uniforms, and Trappings

Cialdini identifies Authority as one of the most reliable ways to persuade because “people defer to experts.” He emphasizes that titles, uniforms, and symbols of expertise (such as diplomas or professional attire) can strongly influence behavior, even when the authority is only implied.
However, he warns that authority must be used ethically. You should not “falsely assume or exaggerate authority,” because people can quickly detect manipulation. Instead, Cialdini advises to “establish your expertise before attempting to exert influence” and to pair it with honesty—such as mentioning a shortcoming before your strengths—to build credibility and trust.

4. Social Proof vs. Coalition

Cialdini defines Social Proof as the tendency to determine what is correct “by finding out what other people think is correct.” When people see that others—especially many others—are doing something, they assume that behavior is the right one. He uses examples such as hotel guests reusing towels when told that most guests do so.
This differs from the influence tactic of Coalition, which involves deliberately aligning with others to increase one’s power in decision-making. Social proof is not coordinated—it’s psychological; it relies on observation of others’ actions rather than forming alliances.

5. Why Social Proof Works Better with Similar Others

Cialdini emphasizes that social proof is strongest when “the proof is provided by the actions of many others just like the person being persuaded.” People are more influenced by those who are similar to them because it makes the behavior appear personally relevant and trustworthy. For example, telling hotel guests that people who stayed in the same room reused towels was more effective than general messages about other guests.

6. Liking

Cialdini identifies several factors that lead to the Liking effect: physical attractiveness, similarity, compliments, and cooperation. People prefer to say yes to those they know and like. He points out that even small similarities or genuine praise can increase the likelihood of compliance. The underlying idea is that when we like someone, we assume their intentions are good and we are more open to persuasion.

7. Scarcity and the Hidden Trap

Cialdini explains that Scarcity increases desirability: “People want more of what they can have less of.” Limited-time offers, exclusive information, or rare opportunities trigger an instinctive reaction to act quickly before losing the chance. He also mentions that this effect is strongest when something becomes newly scarce—when people feel that their freedom to choose is being restricted, they want the item or opportunity even more.