Influence: The Psychology of Persuasion

by Robert B. Cialdini

The principle of social proof states that one important means people use to decide what to believe or how to act in a situation is to examine what others are believing or doing there. Powerful such effects have been found among both children and adults and in such diverse activities as purchase decisions, charity donations, and phobia remission. The principle of social proof can be used to stimulate a person’s compliance with a request by communicating that many other individuals (the more, the better) are or have been complying with it. Therefore, simply pointing to the popularity of an item elevates its popularity. Social proof is most influential under three conditions. The first is uncertainty. When people are unsure, when the situation is ambiguous, they are more likely to attend to the actions of others and to accept those actions as correct. In ambiguous situations, for instance, the decisions of bystanders to offer emergency aid are much more influenced by the actions of other bystanders than when the situation is a clear-cut emergency. A second condition under which social proof is most influential involves “the many”: people are more inclined to follow the lead of others in proportion to the others’ number. When we see multiple others performing an action, we become willing to follow because the action appears to be more (1) correct/valid, (2) feasible, and (3) socially acceptable. The third optimizing condition for social-proof information is similarity. People ...