Twentieth century studies of source credibility were primarily focused on attempts to measure the perceptions of an audience when exposed to a message source. For example, a 1949 study by H.S. Haiman examined the perception shifts among listeners who were exposed to a speech regarding socialized medicine. Three different groups were exposed to the speech; one believing they were listening to then Surgeon General Eugene Dennis, another believing they were listening to the Secretary General of the United States Communist Party, and the last under the impression that they were listening to a random college sophomore. Predictably, the greatest attitude shifts were among the group who believed they were listening to the Surgeon General. (Bettinghaus, p. 91)

Studies like the one mentioned above were relatively simple in that the audience did not have much trouble determining who they believed to be the more credible speaker. Yet, there are a plethora of different cases where a comparison of source credibility would be far more difficult. For example, who is a more credible source? Would the more credible source be the leader of the NAACP or the president of the University of Michigan? Both are prestigious positions held by qualified, learned and respected men and women. To answer such difficult questions, scholars uncovered a number of interesting aspects to source credibility.

Because source credibility is entirely dependant upon audience perceptions of the message source, it is not hard to understand how perceived credibility can vary wildly from one audience member to the other. (p. 91) Additionally, Credibility has much to do with the situation surrounding the communicative event. In some settings the president of the NAACP would be vastly more credible than the president of the University of Michigan. It would seem that source credibility has much to do with an ideal marriage of message content, source charisma and audience openness.

Kenneth Burke’s studies of rhetoric uncovered the notion that source credibility could be heavily influenced through identification. (Berquist et al. p. 218) Burke argues that the essence of persuasion is motivating an audience to identify and adopt the speaker’s positions. To do that, skilled speakers will discover common ground through which to identify with the audience, thereby easing the way for persuasion to occur. (p. 219) It has been noted that humans strive to identify themselves with a particular group. If a source can convince an audience that he or she is in the same group as they are, the audience will generally agree that said source is credible.

Another interesting aspect to the issue of source credibility is the category of humans known as opinion leaders. Lazarsfeld and Menzel’s study of personal influence and the mass media concluded that opinion leaders were those people who were sought out by others for their beliefs regarding specific issues. (Lazarsfeld and Menzel, p. 97.) Generally, opinion leaders are only leaders in one specific area of knowledge. This notion is important to the study of source credibility because it illustrates how we seek out information from others. We look for those people who we know to be knowledgeable about the area in question.

When it comes to measuring credibility, different studies yielded different criteria for determining the relative high or low credibility of a source. However the studies labeled the criteria, they primarily revolved around four main characteristics; competence, trustworthiness, dynamism and co-orientation. (Nelson and Pearson, p. 254)

Competence: A source that is competent can be described as experienced, reliable, informed, knowledgeable and qualified. This characteristic is also dependent upon adequate preparation. Therefore, sources that have reliable research and proof for the argument that is being presented can be described as competent. (p. 254)

Trustworthiness: This characteristic is a sum of qualities that includes honesty, fairness, sincerity and honor. Trustworthiness is a quality that is highly dependent upon the audience’s past experiences and beliefs regarding the source. Thus, sources that are unfamiliar to the audience may find it difficult to establish trustworthiness. (p. 254)

Dynamism: Dynamic sources are bold, outgoing, powerful and assertive. Confidence also has a large impact upon the perceived dynamism of the source. History has proved that a dynamic speaker can sway many an audience to his or her beliefs through impassioned delivery. (p. 255) In the realm of advertising, dynamism is a characteristic that is established through the use powerful images, headlines or copy. The form in which the message is stated can make all the difference in the world.

Co-orientation: This characteristic owes itself largely to Burke’s notion of identification. Co-orientation is the sharing of values, attitudes, beliefs and interests between the message source and the audience. (p. 256)

These four characteristics in sum comprise the whole of source credibility. A message source typically is higher or lower in one particular area as compared to the others. Rarely is a source rated high on all four criteria. Regardless of how a message source is rated, the positive or negative effect of a source’s credibility may be immaterial after a period of several weeks. As noted by Hovland, Janis and Kelly, the relative positive or negative impacts that a source’s credibility has upon the overall persuasiveness of their message generally disappears after several weeks. (Hovland, Janis and Kelly, p. 270.)