Results and Discussion For each of the dimensions except agreeableness, the two groups of subjects differ significantly on their responses to the two speakers. Likewise, the speakers were judged to be significantly different on the measure of attraction. The results are summarized in Table 2. Condition Attraction Table 2 Mean Ratings of Attraction and Five Dimensions of Credibility A multiple correlation analysis was conducted using attraction as the dependent variable and five credibility dimensions as independent variables. The following relationship was found to be significant at the .01 level (F = 4.48, df = 3/242) with a multiple correlation coefficient of .65. Attraction = .29 Agreeableness +.10 Conscientiousness A second multiple correlation program was run in which the five dimensions of credibility, their inverse, their natural logs, and all pairwise multiples were used as independent variables. The following relationship was also significant at the .01 level (F = 5.46, df = 2/243); once again, the multiple correlation coefficient was .65. Attraction = .01 Agreeableness (Culture + As both of the equations account for the same amount of variance, the choice between them is rather arbitrary. While the first is simpler be cause it expresses a linear relationship, the later is more interesting simply because agreeableness appears as a multiplier of the two factors most often cited in the literature on credibility: competence and trustworthiness (or, as here labeled, culture and conscientiousness). It is shown in this analysis that three of the five credibility dimensions are positively and significantly related to an independent measure of the attractiveness of a public speaker who is judged only by those overt cues which the listener perceives during the speech act. One's assessment of interpersonal attraction will change as more information becomes available; this information will in turn intereact with existing judgments to modify or reinforce the evaluation of agreeableness, conscientiousness, and culture. Since those additional variables which contribute to attraction (e.g., shared attitudes, propinquity) may he assumed to have been constant among groups in the experimental study, the dependent variable in the equations above is more properly identified as credibility, a subset of attraction. The following study is an attempt to substaniate the validity of this relationship. EXPERIMENT II Using the findings of the previous analysis, a second study was directed at examining the credibility of the seven leading Presidential candidates (November 1967) in terms of the three dimensions which were found to be significantly related to attraction. Method As the study described here was used to illustrate and partially validate the means of measurement described above rather than to provide a comprehensive assessment of the credibility of the various candidates, no effort was made to select a sample of some voting population. Instead, 126 undergraduates at the University of Illinois were asked to judge one of the seven men on the 12 scales which represent the three dimensions which were being studied. In addition, each subject was asked to rank the seven candidates in order of his preference for President in 1968. The sample included 59 Republicans, 42 Democrats, and 25 who were Independents or expressed no political preference. In order to balance the analysis, the responses of 17 Republican subjects were randomly discarded; there remained an equal number of Republicans and Democrats in the sample. Responses were made between November 13-21, 1967. Results and Discussion The mean ratings for the seven candidates on each of the three dimensions of credibility are represented graphically in Figure 1; each of the dimension evaluations has been normalized to fall within a range of -3 to +3. (The numbers in Figure 1 designate the various candidates by rank order of credibility, represented above in Table 3). For each of the candidates, the mean ratings on each of the dimensions were used in the following equation to arrive at a quantitative measure of credibility: Credibility = .01 Agreeableness (Culture + The scores for the seven candidates appear in rank order in Table 3. The Positions of Seven Presidential Candidates on Three Dimensions of Credibility A comparison of the rank orders of the credibility scores and the Presidential preference scores revealed a significant (p<.05) Spearman correlation of .38. Although this empirical relation may partially validate the methodology, more convincing is a subjective examination of Table 3 and Figure 1. The reader will probably find the results intuitively reasonable for a November 1967 sample of midwestern undergraduates. Because of the insufficiency of the sample in regard to actual voters, a systematic comparison of these findings with nationwide popularity polls could contribute little to the argument being made here. CONCLUSIONS Five personality factors were suggested as underlying dimensions of credibility. Three of these dimensions were found to be significantly related to attraction in an experimental study in which two speakers had been trained to represent the opposite poles of the five hypothesized dimensions. The resulting relationship, expressed as a nonlinear regression equation, was used to assess the credibility of the seven leading Presidential candidates among a sample of University of Illinois undergraduates in November, 1967. The analysis was not meant to represent a particular voter group, but instead to illustrate and partially validate the three dimensions-agreeableness, conscientiousness, and culture-and their relationship to credibility. While it seems reasonable to suggest that the same three dimensions may be applicable to the study of credibility and interpersonal attraction within a given culture, it seems just as reasonable that the relationship among these dimensions may differ significantly among different subcultures. Nevertheless, a framework is suggested here for the study of credibility and interpersonal attraction which could serve as a basis for theoretical description and further empirical study. That the dimension of agreeableness is significantly related to credibility seems to be of some significance in a field of study which has essentially ignored this nonrational dimension. Indeed, without this dimension. it becomes impossible to explain the charismatic appeal of some speakers. In summary, the isolation here of three dimensions of credibility provides empirical support for the three constituents of ethos suggested by Aristotle: "As for the speakers themselves, the sources of our trust in them are there, for apart from the arguments there are three things that gain our belief, namely, intelligence, character, and good will."13 REFERENCES 1. Carl I. Hovland, Irving L. Janis and Harold H. Kelley. Communication and Persuasion. New Haven: Yale University Press, 1953, p. 35. 2. James C. McCroskey. "Scales for the Measurement of Ethos." Speech Monographs 33:65-72, 1966. 3. John Waite Bowers and William A. Phillips. “A Note on the Generality of SourceCredibility Scales." 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