第二个原则是“社会证明”。社会证明是指当一个人(买家)对一件商品感到困惑时，他们可能会看看周围的其他人，然后决定购买。所以当一个人注意到周围的人在买东西时，他们也会考虑买。Cialdini做了一个实验，在这个实验中，亚利桑那酒店的客人被鼓励为了一个社会原因重复使用毛巾。为此项事业提出了四种不同的主张。研究结果表明，顾客可以推断出他们之前的人为慈善事业捐款的迹象是重复使用毛巾次数最多的群体(Cialdini, 2001)。第三个原则是“承诺和一致性”。卖方必须承诺完成交易。人们会更倾向于相信一个表现出承诺和一致性的卖家。如果客户被要求以更公开的方式承诺，那么他们很有可能会继续购买。“喜欢”是一种说服的武器，Cialdini说这将有助于达成交易。喜欢可以是基于外表吸引力的东西，也可以是因为买家喜欢和自己相似的卖家，或者因为卖家可能和买家有相似的名字等等(Cialdini, 2001)。
我们做了一个实验，随机的表格被邮寄给顾客。顾客被要求填写表格，然后寄回给卖家。表格上注明了卖方名称。大多数客户填写表单时，他们的姓名与发件人相似。Cialdini的“权威”原则是他认为说服是可能的。如果卖方的信誉以外部形象、权威语气等形式建立良好，那么很有可能更容易说服相关方(Schaefer, 2012)。Stanley Milgram在1974年进行的一项实验中发现，当权威人士通知参与者时，他们可能愿意尝试一些他们在现实生活中可能不会这样做的例子(Milgram, 1974)。使用“稀缺性”的外观是说服客户购买的一种方法(Cialdini, 2001)。某些东西越稀有，消费者就越想购买。消费者可能认为，产品的稀有性实际上与受欢迎程度有关，或者他们的同行正在购买该产品，因此该产品是稀有的。当营销人员想要完成交易时，这可以作为一种说服技巧。
The second principle is that of ‘social proof’. Social proof is those situations where when a person (the buyer) is confused about a purchase they might look at other people around them and then they will decide to buy. So when a person notices that people around them are buying something, then they also consider buying it. Cialdini conducted an experiment in which Arizona hotel visitors were encouraged to reuse towels for a social cause. Four different signs were put up to advocate for this cause. The study results showed that the signs from which the customer could infer that people before them had donated for the cause, were the groups that reused their towels the most (Cialdini, 2001). The third principle is that of ‘commitment and consistency’. The seller must show a commitment towards closing the deal. People would be more apt to trust a seller who shows commitment and consistency. Where a customer is asked to commit in a more public manner, then the chances are that they will follow through with their purchase. ‘Liking’ is a weapon of persuasion which Cialdini states would be helpful in closing a deal. Liking could be something based on physical attractiveness or it could because the buyer likes the seller for being similar to themselves or because the seller might have a similar name as the buyer etc. (Cialdini, 2001).
An experiment was conducted where random forms were being mailed out to customers. Customers were asked to fill out the forms and mail it back to seller. Seller name was indicated in the forms. The majority of the customers filled in the forms when they had a name which was similar to the sender. Cialdini’s principle of ‘authority’ is one by which Cialdini states that it is possible to persuade. Where seller credibility is well established in the form of external appearance authoritative tone and more, the chances are that it might be easier to persuade the party involved (Schaefer, 2012). In a 1974 experiment conducted by Stanley Milgram, it was established that when informed by authority, participants might be willing to try out some instances that they might not do so in real life (Milgram, 1974). Using an appearance of ‘scarcity’ is one way to convince the customer to make a purchase (Cialdini, 2001). The rarer something is shown to be the more the consumer might want to make the purchase. The consumer might believe that the rarity of the product is actually associated with popularity or that their peers are buying the product and hence the product is rare. This could be used by the marketer as a persuasion technique just when they want to close the deal.