James C. McCroskey and Walter H. Combs

This study examined the effects of two types of analogy on attitude change and source credibility. Subjects were exposed to either a literal, figurative, or no-analogy message. Comparison of attitude change scores and terminal source credibility ratings by message condition indicated that both the literal and figurative versions produced greater attitude change than the no-analogy version. Differences in source credibility ratings were not attributable to the use of analogy. The authors discuss the need for further research in the area and present two tentative explanations of their findings.

The use of analogy as a device to increase the effectiveness of a message is generally supported by authors of English composition, public speaking, and persuasion textbooks. Most of these writers refer to the analogy as either a "form of support" or "pattern of reasoning." Both these definitions assume that the persuasive impact of a message containing an analogy will be greater than one not containing such a device.

To the knowledge of the writers, no one has systematically investigated the effects of analogy in a persuasion setting. The purpose of the present study was to examine the effects of two types of analogy on attitude change and source credibility. Specifically, we compared the effects of messages containing a literal or a figurative analogy with each other and with a message not containing an analogy.

Rationale and Hypotheses

Metaphors, similes and analogies all make comparisons between known and unknown concepts. However, these "figures of speech" differ in form and the extent to which they attempt to relate meaning. The analogy may attempt to point out several areas of similarity while the metaphor and simile limit the comparison to the one area. An entire message may consist of statements relating the unknown to the known by means of analogy. Therefore, the analogy should denote the meaning of a message more clearly than a comparable message not containing such a figure of speech.

Little empirical evidence is available in the literature to corroborate the views of advocates of the use of figures of speech in persuasive messages. Bowes [3] found that certain types of metaphor are judged as extremely intense. In an earlier study he reported [2] that a highly intense persuasive speech was less effective in changing attitudes than a less intense speech. Bowers and Osborn [4] found that certain intense concluding metaphors produced more attitude change in the direction advocated by the source than did literal counterparts. Changes in source credibility ratings indicated that no concrete generalizations could be made concerning the relationship between use of the metaphor and source credibility.

If the use of an analogy does in fact increase the clarity of a message, one might expect more attitude change associated with this type of manipulation than with a comparable message not containing an analogy. Therefore, our hypothesis was: messages containing an analogy will produce greater attitude change than a comparable message not containing an analogy. No directional predictions were made concerning the relationship between source credibility and use of analogy.



Subjects were students enrolled in a basic public speaking course at Michigan State University during Fall term, 1968. A total of 528 subjects were randomly assigned to one of six experimental conditions (n in the conditions ranged from 86 to 91). The experiment was conducted in conjunction with a speech evaluation project. This project was given to students as part of a routine classroom assignment.

Independent Variables: Message Type and Source Credibility

The experimental treatment consisted of exposure to one of three messages analogy conditions: literal, figurative, and no analogy. Each message condition presented arguments critical of the U.S. foreign aid program for Brazil. The literal version compared U.S. foreign aid for Brazil to the U. S. urban renewal program. The figurative version compared U. S. foreign aid for Brazil to a snowstorm. The no-analogy condition contained no comparison statements. Only narrative statements describing failures of the U.S. foreign aid program for Brazil were included in this version.

All message conditions were paired with either a high- or low-credible source. Source credibility was manipulated by attributing each message to the low-credible source (Lin Tai, ambassador to Brazil from Red China) or to the high-credible source (Charles L. Wilson, former U.S. ambassador to Brazil). Each message was approximately 400 words in length and was presented as a written quotation from one of the two sources. The quotations were attributed to articles taken from a July 15, 1968 edition of the Washington Post.

Measurement and Administration

Subjects were given a booklet containing an attitude pretest on the topic, material for another study which required approximately 30 minutes for completion, a message, an attitude post-test, and a set of terminal source credibility rating scales. Subjects were instructed in the need for their assistance, the importance of research in communication, and in how to fill out semantic differential attitude scales.

Prior to exposure to one of the message conditions, each subject completed a number of semantic differential-type scales for several concepts, on of which was: "The U.S. has a well administered foreign aid program for Brazil." The scales used were: Right-Wrong, False-True, Yes-No, Incorrect-Correct, I agree-I disagree. After subjects had evaluated several of these concepts, and had completed an unrelated study, they were asked to turn to the next page in their booklets. This page contained the initial credibility induction, a message, and an attitude post-test.

The last page of the booklet, the credibility test, contained scales developed by McCroskey [6] for "authoritativeness" and "character" and Berlo, Lemert and Mertz [1] for "dynamism." Six scales were employed for each dimension.

The above procedures were repeated in 32 sections of the basic public speaking course.

Design and Statistical Analysis

The message and source credibility manipulations generated a 3 X 2 design. Pre and post measures for attitude toward the topic and a post-test source credibility measure consisting of scores from the authoritativeness, character, and dynamism dimensions, were obtained for each subject.

The .05 criterion was set for significance in all statistical tests (one-tailed where appropriate). Analysis of pretests attitude scores showed no significant differences among message and credibility condition groups. Therefore, pre-post difference scores were analyzed in a 3 X 2 analysis of variance. Observed significant differences for the message condition variable were examined by means of t-tests. Credibility scores were analyzed in a 3 X 2 analysis of variance.


Credibility Inductions

The credibility inductions appeared to be appropriate in that significant differences in the intended direction, attributable to initial credibility, were observed on attitude change and terminal credibility scores for all dimensions of source credibility.

Attitude Change

Significant main effects were observed for initial credibility (F = 4.65, p < .05) and message type (F = 2.64, p < .05). No significant initial credibility-by-message interaction was present. Results of subsequent t-tests indicated that both the literal and figurative analogy conditions produced significantly greater attitude change than the no analogy condition (literal, t =2.11, p < .05; figurative, t = 1.85, p < .05) but were not significantly different from each other. (See Table 1).

Source Credibility

Analysis of variance of terminal source credibility scores indicated significant differences attributable to initial credibility on all dimensions (Authoritativeness, F = 215.54, p < .05; Character, F = 65.10, p < .05; Dynamism, F = 4.26, p < .05). The initially high-credible source was perceived to be more authoritative, of higher character, and more dynamic than the initially low credible source. No significant differences attributable to message condition or to interaction of initial credibility and message condition were observed on any of the three dimensions of terminal source credibility.


Means for Attitude Change and Terminal Source Credibility

Initial Credibility Dependent Variable Message Condition
Literal Figurative No Analogy
Attitude Change 5.70 5.04 3.12
High Authoritativeness 35.16 35.17 34.27
Character 26.52 27.33 26.54
Dynamism 33.43 32.62 32.64
Attitude Change 3.40 3.64 2.60
Low Authoritativeness 27.26 26.92 27.73
Character 23.44 23.80 24.03
Dynamism 31.75 31.60 32.01


The results obtained from this study support our hypothesis that a message containing an analogy produces greater attitude change than one not containing an analogy. In this particular experiment, the literal and figurative analogies were equally effective in producing such a result. Inspection of the means by message condition indicated that attitude change scores were somewhat higher when initial credibility was also high, though the interaction between these two variables was not significant.

These findings lend support to the advocates of the use of analogies in persuasive messages. Generalization of these results of all situations involving potential use of analogies, of course, is premature. Replication of this study, using a number of analogy conditions, non-analogy conditions, topics, and types of experimental subjects is needed in order to determine whether or not the present results represent a consistent finding.

Several factors may have contributed to the observed differences in this study. One is the problem of constructing comparable messages. Though the investigators attempted to control for this problem by holding length and content constant, it could be argued that the differences in attitude change were due in part to unequal messages. Future studies should employ messages of varying length and content to test for this effect.

Another factor is the message position variable. The present study used only a negative position. Whether or not the position of the message interacts with the analogy cannot be determined from this experiment.

Finally, the message topic needs to be examined in conjunction with the analogy. Some topics may provide the source with a greater number of analogies than others. One could also argue that a receiver's level of familiarity with the topic or with the elements of comparison in the message influence attitude change.

Given the above limitations of this study, two explanations of the results are presented for consideration.

1. The use of an analogy helps define the meaning of a message more clearly. An analogy, by definition, contains two sets of elements: those familiar to a receiver and those unfamiliar. The analogy connects or relates these elements in the message. Assuming these stimuli produce associations (i.e. meaning) in a receiver, it can be argued that a message linking these elements is more effective because it produces three sets of associations: those due to the known or familiar elements, those due to the unknown or unfamiliar elements, and those due to the linking of known to unknown elements.

2. The use of an analogy decreases a receiver's ability to employ "selectivity" as an alternative to attitude change. Rosenberg [7] suggests that selectivity operates under two conditions: "where the situation is unstructured or ambiguous and where the range of options is wide." In a persuasion setting a number of options are available to a receiver. For example, he may derogate the source, attend only to portions of the message, re-define the meaning of the message consistent with his own attitudes, ignore the message, and/or forget the contents of the message. These potential responses have been labeled selective exposure, selective perception, and selective retention [5]. Given that selectivity operates in a persuasive setting, the analogy may help limit the number of alternatives to attitude change. As these alternative responses are blocked, the probability that attitude change will occur increases.

These tentative explanations need further investigation. More data is necessary before it will be possible to explain how the analogy functions in increasing or decreasing the persuasiveness of messages. The results of the present study suggest that inclusion of an analogy in a message may increase its persuasive impact.


1. Berlo, David K., James B. Lemert, and Robert J. Mertz. "Dimensions for Evaluating the Acceptability of Message Sources." Research Monograph, Department of Communication, Michigan State University, 1966.

2. Bowers, John W. "Language Intensity, Social Introversion, and Attitude Change." Speech Monographs 30:345-52, 1963.

3. -----. "Some Correlates of Language Intensity." Quarterly Journal of Speech 50:415-20, 1964.

4. Bowers, John W. and Michael M. Osborn. "Attitudinal Effects of Selected Types of Concluding Metaphors in Persuasive Speeches." Speech Monographs 33:147-55, 1966.

5. Klapper, Joseph T. "Mediating Factors in the Service of Conversion." In: The effects of Mass Communication New York: The Free Press, 1960, p. 18-26.

6. McCroskey, James C. "Scales for the Measurement of Ethos." Speech Monographs 33:65-72, 1966.

7. Rosenberg, Morris "Psychological Selectivity in Self-esteem Formation." In: Attitude, Ego Involvement and Change. (Edited by Carolyn W. and Muzafer Sherif) New York: Wiley, 1967, p. 31.

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