Dr. Robert B. Cialdini, Professor of Psychology at Arizona State University, has spent over fifteen years in the scientific investigation of the processes whereby people are persuaded and reach their decisions. He enumerates six fundamental social and psychological principles underlying the thousands of individual tactics that successful persuaders or compliance practitioners use every day to get us to say yes.

*These principles are:

Rule of Reciprocity
According to sociologists and anthropologists, one of the most widespread and basic norms of human culture is embodied in the rule of reciprocity. The rule requires that one person try to repay, in kind, what another person has provided. By obligating the recipient of an act to repayment in the future, the rule for reciprocation allows one individual to give something to another with confidence that it is not being lost. This sense of future obligation within the rule makes possible the development of various kinds of continuing relationships, transactions, and exchanges that are beneficial to the society. Consequently, all members of the society are trained from childhood to abide by the rule or suffer serious social disapproval. The decision to comply with another's request is frequently influenced by the reciprocity rule. One favorite and profitable tactic of certain compliance professionals is to give something to another before asking for a return favor. The exploitability of this tactic is due to three characteristics of the rule for reciprocation:

1. the rule is extremely powerful, often overwhelming the influence of other factors that normally determine compliance with a request;
2. the rule applies even to uninvited first favors, thereby reducing our ability to decide whom we wish to owe and putting the choice in the hands of others;
3. the rule can spur unequal exchanges; to be rid of the uncomfortable feeling of indebtedness, an individual will often agree to a request for a substantially larger favor than the one he or she received. Another way that the rule for reciprocity can increase compliance involves a simple variation on the basic theme: instead of providing a first favor that stimulates a return favor, an individual can make an initial concession that stimulates a return concession. One compliance procedure, called the rejection-then-retreat technique, or door-in-the-face technique, relies heavily on the pressure to reciprocate concessions. By starting with an extreme request that is sure to be rejected, a requester can then profitably retreat to a smaller request (the one that was desired all along), which is likely to be accepted because it appears to be a concession. Research indicates that, aside from increasing the likelihood that a person will say yes to a request, the rejection-then-retreat technique also increases the likelihood that the person will carry out the request a will agree to future such requests. Our best defense against the use of reciprocity pressure to gain compliance is not systematic rejection of the initial offers of others. Rather, we should accept initial favors or concessions in good faith, but be ready to redefine them as tricks should they later be proved as such. Once they are redefined in this way, we will no longer feel a need to respond with a favor or concession of our own.
    

Commitment and Consistency
People have a desire to look consistent within their words, beliefs, attitudes and deeds...this tendency is fed from three sources:

• good personal consistency is highly valued by society;
• consistent conduct provides a beneficial approach to daily life;
• a consistent orientation affords a valuable shortcut through the complexity of modern existence: by being consistent with earlier decisions, one reduces the need to process all the relevant information in future similar situations; instead, one merely needs to recall the earlier decision and respond consistently with it. The key to using consistency pressures for profit is the initial commitment: after making a commitment (that is taking a stand or position), people are more willing to agree to requests that are in keeping with the prior commitment. Many compliance professionals try to induce people to take an initial position that is consistent with a behavior they will later request from these people. Commitments are most effective when they are active, public, effortful, and viewed as internally motivated (uncoerced). Once a stand is taken, there is a natural tendency to behave in ways that are stubbornly consistent with the stand. The drive to be (and look) consistent constitutes a highly potent weapon of social influence, often causing us to act in ways that are clearly contrary to our own best interests. Commitment decisions, even erroneous ones, have a tendency to be self-perpetuating because they can "grow their own legs." That is, people often add new reasons and justifications to support the wisdom of commitments they have already made. As a consequence, some commitments remain in effect long after the conditions that spurred them have changed. This phenomenon explains the effectiveness of certain deceptive compliance practices. To recognize and resist the undue influence of consistency pressures on our compliance decisions, we should listen for signals coming from two places within us: our stomachs and our heart of hearts. Stomach signs appear when we realize that we are being pushed by commitment and consistency pressures to agree to requests we know we don't want to perform. Heart of heart signs are best employed when it is not clear to us that an initial commitment was wrongheaded. Here, we should ask ourselves a crucial question, "Knowing what I know, if I could go back in time, would I make the same commitment?"

Social Proof
One means we use to determine what is correct is to find out what other people think is correct. We view a behavior as more correct in a given situation to the degree that we see other performing it. The principle of social proof can be used to stimulate a person's compliance with a request by informing the person that many other individuals (the more, the better, the more "famous" the better) are or have been complying with it. This weapon of influence provides us with a shortcut for determining how to behave, but, as the same time, makes one who uses the shortcut vulnerable to the attacks of profiteers who lie in wait along its path (introduction seminars or guest dinners, retreats to recruit cult members--provide the models of the behavior the group wants to produce in the new recruit) Social proof is most influential under two conditions:

• 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);
• similarity (people are more inclined to follow the lead of similar others) Recommendations on how to reduce our susceptibility to faulty social proof include a sensitivity to clearly counterfeit evidence of what similar others are doing and a recognition that the actions of similar others should not form the sole basis for our decisions.

Liking
People prefer to say yes to individuals they know and like. This simple rules enables us to learn about factors that influence the liking process by examining which factors compliance professionals emphasize to increase their overall attractiveness and their consequent effectiveness. Compliance practitioners regularly use several such factors. One feature of a person that influences overall attractiveness is physical attractiveness. Although it has long been suspected that physical beauty provides an advantage in social interaction, research indicates that the advantage may be greater than supposed. Physical attractiveness seems to engender a "halo" effect that extends to favorable impressions of other traits such as talent, kindness, and intelligence. As a result, attractive people are more persuasive both in terms of getting what they request and in changing others' attitudes. A second factor that influences liking and compliance is similarity. We like people who are like us and are more willing to say yes to their requests, often in an unthinking manner. Another factor that produces liking is praise; although they can sometimes backfire when crudely transparent, compliments general enhance liking, and thus, compliance. Increased familiarity through repeated contact with a person or thing is yet another factor that normally facilitates liking. But this relationship holds true principally when the contact takes place under positive rather than negative circumstances. One positive circumstance that works especially well is mutual and successful cooperation. A fifth factor linked to like is mere association. By connecting themselves or their products with positive things, merchants of influence frequently seek to share in the positivity through the process of association. Other individuals as well appear to recognize the effect of simple connections and try to associate themselves with favorable events and distance themselves from unfavorable events in the eyes of observers. A potentially effective strategy for reducing the unwanted influence of liking on compliance decisions requires a special sensitivity to the experience of undue liking for a requester. Upon recognizing that we like a requester inordinately well under the circumstances, we should step back from the social interaction, mentally separate the requester from his or her offer, and make any compliance decision based solely on the merits of the offer

Authority
In the Milgram studies of obedience, we can see evidence of a strong pressure in our society for compliance with the requests of an authority. The strength of this tendency to obey legitimate authorities comes from systematic socialization practices designed to instill in society members the perception that such obedience constitutes correct conduct . In addition, it is frequently adaptive to obey the dictates of genuine authorities because such individuals usually possess high levels of knowledge, wisdom, and power. For these reasons, deference to authorities can occur in a mindless fashion as a kind of decision-making shortcut. When reacting to authority in an automatic fashion, there is a tendency to do so in response to the mere symbols of authority rather than to its substance. Three kinds of symbols that have been shown by research to be effective in this regard are

• titles;
• clothing;
• automobiles. In separate studies investigating the influence of these symbols, individuals possessing one or another of them (and no other legitimizing credentials) were accorded more deference or obedience by those they encountered. Moreover, in each instance, those individuals who deferred or obeyed underestimated the effect of authority pressures on their behaviors. It is possible to defend ourselves against the detrimental effects of authority influence by asking two questions: Is this authority truly an expert? How truthful can we expect this expert to be here? The first question directs our attention away from symbols and toward evidence for authority status. The second advises us to consider not just the expert's knowledge in the situation but also his or her trustworthiness. With regard to this second consideration, we should be alert to the trust-enhancing tactic in which a communicator first provides some mildly negative information about him- or herself. Through this strategy the person creates a perception of honesty that makes all subsequent information seem even more credible to observers.
   

Scarcity
According to the scarcity principle, people assign more value to opportunities when they are less available. The use of this principle for profit can be seen in such compliance techniques as the "limited number" and "deadline" tactics, wherein practitioners try to convince us that access to what they are offering is restricted by amount or time. The scarcity principle holds true for two reasons:

• because things that are difficult to attain are typically more valuable, the availability of an item or experience can serve as a shortcut cue to its quality;
• as things become less accessible, we lose freedoms. According to psychological reactance theory, we respond to the loss of freedoms by wanting to have them (along with the goods and services connected to them) more than before. As a motivator, psychological reactance is present throughout the great majority of the life span. However, it is especially evident at a pair of ages: "the terrible twos" and the teenage years. Both of these times are characterized by an emerging sense of individuality, which brings to prominence such issues as control, rights, and freedom. Consequently, individuals at these ages are especially sensitive to restrictions. In addition to its effect on the valuation of commodities, the scarcity principle also applies to the way that information is evaluated. Research indicates that the act of limiting access to a message causes individuals to want to receive it more and to become more favorable to it. The latter of these findings--that limited information is more persuasive--seems the more interesting. In the case of censorship, this effect occurs even when the message has not been received. When a message has been received, it is more effective if it is perceived as consisting of exclusive information. ("We" have the truth....we have special knowledge).

 
The scarcity principle is most likely to hold true under two optimizing conditions:

• scarce items are heightened in value when they are newly scarce (we value those things that have become recently restricted more than those that were restricted all along);
• we are most attracted to scarce resources when we compete with others for them. It is difficult to steel ourselves cognitively against scarcity pressures because they have an emotion-arousing quality that makes thinking difficult. In defense, we might try to be alert to a rush of arousal in situations involving scarcity. Once so alerted, we can take steps to calm the arousal and assess the merits of the opportunity in terms of why we want it.
  
  *Taken from Influence. Science and Practice, Robert B. Cialdini, Scott, Foresman and Company, 1985; Summary notes.