says what to whom with what effect? Janis and Holvand (1959) present a paradigm of interacting factors that enter into successful persuasion (see Figure 1). Communicator characteristics, the content of the message, the manner of presentation, and other crucial situational factors shown in column 1 are considered to be stimulus variables capable of touching off the key mediating processes (represented in column 3)-attention, comprehension, and acceptance-that give rise to the various effects designated as attitude change (column 4). The magnitude of the influence exerted by the stimulus variables also depends on different types of predispositional variables (represented in column 2).

• The categories and subcategories are not necessarily exhaustive but highlight the major types of stimulus variables that play a role in producing changes in verbalizable attitudes.

Source: Based on Janis and Hovland 1959.

Figure 1-Major factors in persuasion

PERCEPTION
CHANGE

AFFECT CHANGE

ACTION CHANGE

Communicator and content factors. The most thoroughly investigated propositions bearing on the processes of persuasion are those that specify how one or another of the stimulus attributes is related to successful persuasion. Sometimes communications research has merely confirmed certain of the well-known prescriptions formulated by experts in the art of persuasion. But research occasionally leads to the discovery of unexpected limiting conditions or hitherto unknown relationships that call into question the commonly accepted assumptions about how people can be influenced to change their beliefs or attitudes.

Prestige and "sleeper" effects. Studies of prestige effects have confirmed some "obvious" assumptions and refuted other, equally "obvious" ones. Several communication experiments have shown, as might be expected, that there is an immediate gain in acceptance of persuasive communications when the message is given by someone who is initially accorded relatively high prestige by the audience or when the arguments are attributed to a relatively trustworthy source. But, contrary to expectations, it has been found that in the long run, persuasive communications from low-prestige sources turn out to be just as effective as those from high-prestige sources. This phenomenon has been termed the "sleeper" effect (see Hovland et al. 1953, pp. 254-259; Kelman & Hovland 1953). Both positive and negative prestige effects seem to wear off over a period of several weeks. When a communication comes from a nonprestigious or distrusted source, the audience tends at first to reject the message. But as time goes on, acceptance of the originally discounted statements has been found to increase, evidently because with the passage of time, the content of the message is no longer spontaneously associated with the

source.

One-sided versus two-sided presentations. Another issue that has been systematically investigated is whether persuasion is more effective when it concentrates exclusively on the arguments supporting the propagandist's position or when it includes discussion of the opposing arguments. Hitler and other Nazi propaganda strategists have claimed that in appealing for a specific line of action, no rival or opposing ideas should ever be mentioned, because they invite comparisons, hesitation, and doubt. But the available evidence indicates that this principle holds true only under very limited conditions, such as when the audience is unaware of the arguments for the other side of the issue. When the audience is strongly opposed to the position being advocated, a persuasive message is generally more effective if it includes the opposing arguments than if it presents only the arguments in favor of one side of the issue (see Hovland et al. 1953, pp. 105-110; Hovland et al. 1949, pp. 201-227; Klapper 1960, pp. 113-116). Moreover, even when the audience is not initially opposed to the communicator's position, a two-sided presentation will be more effective in creating sustained changes in attitudes if the communication is given under conditions where the audience will subsequently be exposed to countercommunications presenting the opposing arguments.

Inoculation devices. When the members of an audience are pre-exposed to the opposing arguments along with some refutations, they are to some extent "inoculated" against subsequent countercommunications, because the new arguments will be much less impressive and more readily discounted (see Lumsdaine & Janis 1953). This type of inoculation has been found to produce a "generalized immunization effect" under certain conditions, notably when a communication advocates recommendations that the audience already regards as being in line with commonly accepted norms, such as simple health rules. Thus, inclusion of a few arguments that momentarily shake the confidence of members of the audience in cultural truisms they had always taken for granted will reduce the chances of their being influenced by subsequent counterpropaganda, because they become more resistant both to the counterarguments specifically mentioned and refuted in the original two-sided communication and to new counterarguments which might otherwise shake their beliefs (McGuire 1961).

Another simple inoculation device has been found to be effective in reducing the influence of unconventional communications that take issue with cultural truisms of the type that people are seldom or never called upon to defend. This device consists of stimulating the members of an audience to build up defenses by warning them in advance that their hitherto unchallenged beliefs will soon be exposed to strong attack (McGuire 1961; 1964; McGuire & Papageorgis 1962).

The well-known "freezing" effects of public commitment to a newly adopted policy or course of action form the basis for another type of communication device that prevents backsliding. Experimental studies indicate that resistance to subsequent countercommunications can be built up if, after presenting impressive arguments and appeals, the communicator uses his persuasive influence to induce his listeners to endorse the position publicly-for example, by voting openly for it, signing a petition, or showing other overt signs of acceptance that will be seen by people in their community (see Lewin 1947; Attitude Organization and Change 1960).

Other types of inoculation procedures have been studied to determine the conditions under which acceptance of a new attitude or policy recommendation will be sustained despite subsequent exposure to frustrations, threats, or setbacks that arouse strong negative effects. For example, after having been persuaded to adopt a communicator's recommendations, the audience may subsequently be exposed to warnings or punishments that stimulate avoidance of the recommendations. The emotional impact of the subsequent setback will tend to be reduced if the audience has been given inoculating communications that predict the threatening event in advance, thus eliminating the element of surprise and, at the same time, stimulating appropriate defenses (see Janis 1962). Similarly, in the case of "bad news" events that generate pessimistic expectations about the future, preparatory communications that present grounds for

maintaining optimistic expectations can help soften the blow and enable the audience to resist being unduly influenced by the impact of the disturbance (Janis et al. 1951). In general, the eventual success of any attempt at persuading people to carry out a given course of action is likely to be attained if the communicator frankly discusses the possible subsequent difficulties and countercommunications, presenting them in a way that helps to create a cognitive frame of reference for discounting or minimizing them if they do, in fact, materialize.

Effectiveness of "primacy." Since most inoculation devices involve familiarizing the audience with counteraguments, two-sided communications might be more advantageous in the long run, even in circumstances where a one-sided communication could be expected to be more successful in producing immediate changes in a higher proportion of the audience. There are, of course, many different ways of arranging the opposing arguments in a two-sided communication, and some ways of inserting them have been found to be more effective than others. For example, when the audience is not familiar with the opposing arguments, a twosided communication from an authoritative source tends to be more effective if the opposing arguments are presented after, rather than before, the favorable arguments that support the communicator's conclusion. By giving strong favorable arguments first, the communication arouses the audience's motivation to accept the communicator's conclusion, so that when the negative material subsequently occurs, it can be better tolerated. Furthermore, if a strong case is made for the communicator's position at the outset, there is a greater likelihood that the recipient will make an early decision to accept the communicator's position and thereafter tend to minimize dissonance or conflict by ignoring the opposing ideas (see Brehm & Cohen 1962; Festinger 1957; 1964; Janis 1957; 1959). This primacy effect, when tested with communications designed to induce opposing attitudes toward the same social objects or policies, proved to be extremely pronounced under conditiions where the contradictory material was not spontaneously salient and there was no time interval between the first set of arguments and the second, contradictory set (Asch 1946; Luchins 1957a; 1957b; Janis & Feierabend 1957). Under other conditions, however, such as where the audience is very familiar with the opposing arguments and has initial doubts about the communicator's honesty, a recency effect might predominate, making it more advantageous to give the counterarguments first, with the main affirmative arguments saved for the end of the communication (see Hovland et al. 1957, pp. 130-147.)

Emotional appeals. It is commonly recognized that when a person remains unmoved by repeated attempts to persuade him with rational arguments, he might nevertheless show a marked change as soon as emotional appeals are introduced. Probably the most widespread form of emotional appeal in modern Western culture involves the arousal of fear by emphasizing anticipated threats. Antiwar propaganda, public health

campaigns, and other efforts at mass persuasion frequently rely upon emotional shock devices to motivate people to carry out preventive measures or to support policies designed to avert potential dangers (for example, promoting a ban against a nuclear weapons test by emphasizing the horrors of war). For maximal effectiveness, this device requires not only that the communications succeed in arousing fear but also that the recommendations function as effective reassurances. The latter term

refers

to verbal statements-plans, resolutions, judgments, evaluations-that are capable of alleviating or reducing emotional tension. Many communication experiments have been designed to test popular claims about the effectiveness of emotional appeals and to determine objectively the conditions under which such appeals are successful.

Political leaders and public health authorities often assume that the protective actions or practical solutions they advocate will be more readily accepted, the more they succeed in frightening the audience about the dangerous consequences of failing to adhere to their recommendations. This assumption may occasionally be correct, as in the case of recommendations concerning immediate escape actions (e.g., evacuation of a danger area within a few minutes after an emergency warning is issued). But the assumption appears to be questionable in many instances, especially when the goal is to induce delayed actions or sustained attitudes (e.g., evacuating at some future date, if the threat materializes; supporting a disarmament movement; favoring prodemocratic policies). The available evidence indicates that presenting fear-arousing material in a persuasive communication tends to stimulate the recipient's vigilance and his need for reassurance. But this does not necessarily increase his motivation to accept authoritative recommendations about ways to avert or cope with the danger, since the person may find other ways to reduce his fear. Whenever fear is aroused to a very high level, resistances tend to be strongly mobilized. This will reduce the effectiveness of a persuasive communication, unless it is outweighed by certain other factors that could facilitate attitude change (Hovland et al. 1953, pp. 56-98; Leventhal 1965). Among the facilitating conditions that increase an audience's tolerance for a strong dosage of fear-arousing material in a persuasive message is the inclusion of one or more highly specific recommendations that offer an apparently good solution to the problems posed by the threat, with no obvious loopholes (Leventhal et al. 1965). When this condition is not met, as is often the case in "scare" propaganda, the use of a strong emotional appeal may produce much less acceptance of the communicator's recommendations than a milder appeal, since the audience will then become motivated to attach little importance to the the threat or develop some other form of defensive avoidance that enables them to alleviate their fear. Sometimes strong emotional appeals attain spectacular persuasive effects, but it is difficult to predict accurately that a very high dosage of fear will not exceed the optimal level. Preliminary "program assessment" research with cross-sectional samples of the intended