Source credibility is "a term commonly used to imply a communicator's positive characteristics that affect the receiver's acceptance of a message." Academic studies of this topic began in the 20th century and were given a special emphasis during World War II, when the US government sought to use propaganda to influence public opinion in support of the war effort. Psychologist Carl Hovland and his colleagues worked at the War Department upon this during the 1940s and then continued experimental studies at Yale University. They built upon the work of researchers in the first half of the 20th century who had developed a Source-Message-Channel-Receiver model of communication and, with Muzafer Sherif, (Muzaffer Şerif Başoğlu) developed this as part of their theories of persuasion and social judgement.
Overview Source credibility theory is an established theory that explains how communication's persuasiveness is affected by the perceived credibility of the source of the communication. The credibility of all communication, regardless of format, has been found to be heavily influenced by the perceived credibility of the source of that communication.
The idea of credibility was first derived from Aristotle who argued that the speaker's reliability must be built and established in speech and that what the speaker did or said before such a speech was not of importance. Aristotle divided the aspects of persuasion into three categories: ethos (credibility), pathos (emotion) and logos (logic). As credibility refers to people believing whom they trust, emotion and logic indicate a person's emotional connection and means of reasoning to convince one of a particular argument and/or speech. The area of source credibility is studied for practical applications in communication, marketing, law, and political science.
Dimensions There are several dimensions of credibility that affect how an audience will perceive the speaker: competence, extraversion, composure, character, and sociability. These dimensions can be related to French & Raven's five bases of power (see below). These characteristics are fluid and affect each other as well as the speaker's transactional credibility. One dimension may strengthen the speaker's credibility if he/she struggles in another.
The audience can perceive these attributes through certain behaviors in which the speaker delivers results, is concise and direct with the audience members. If a speaker displays characteristics of honesty, integrity, sincerity, and can show that they are trustworthy and ethical, the audience will be more inclined to believe the message being communicated to them, even if they do not remember every aspect of the interaction. They will, however, recall how the presenter made them feel, how they took in the information and what they may share with others once the presentation has concluded.
For instance, if a speaker presents the audience with a short clip and includes a witty joke at the conclusion of the video to drive the point home, members of the audience may only remember the joke. Although the joke may only be a small element of the entire speech, someone will recall it and share it with others and perhaps speak kindly of the speaker and wish to interact with that person again, or promise to purchase product or feel inclined to tell anyone who will listen about what they learned. This is when terminal credibility comes into play, but is dependent on how well the speaker presented the information to the audience.
Speakers must also present themselves to be likable since people are more inclined to trust those they generally like or feel comfortable with in a room. Being friendly, easy going, warmhearted, nice and kind can carry the speaker into a very comfortable space with the audience. Once the audience is at ease, the speaker can generally present their information, and it will be perceived positively.
The late Dr. James C. McCroskey (University of Alabama at Birmingham) was known for his research in the dimensions of source credibility. His scales for the measurement of source credibility have been widely used in communication research. He noted in his 1975 article, "Image of Mass Media News Sources", that "the available scales for the measurement of source credibility should not be assumed to be universally applicable measures of source credibility." However, his research and his proposed scale from 1975 are still foundations for source credibility research.
In McCroskey's work, he further breaks down each dimension as follows:
Competence
The measurement of competence is based on seven values. These values are qualification, expertise, reliability, believability, openness (i.e. intellectual vs. narrow), value, and currency (i.e., informed vs. uninformed).
Character
The measurement of character has four values. These are kindness, sympathy, selflessness (i.e., unselfish vs. selfish), and virtue.
Sociability
The measurement of sociability has three values. These are friendliness, cheer, and temperament (i.e., good natured vs. irritable). Character and sociability may be combined by some researchers. In that case, researchers will employ the seven values under one "Character-Sociability" measurement.
Composure
Four seemingly synonymous values are assigned to the measurement of composure. These are excitability (composed vs. excitable), calmness (calm vs. anxious), tension (relaxed vs. tense), and poise (poised vs. nervous).
Extroversion
Like composure, extroversion is composed of four seemingly synonymous values. These are aggressiveness, boldness, talkativeness (i.e. talkative vs. silent), and voice (i.e., verbal vs. quiet).
Dr. McCroskey's research concluded that of the five dimensions of credibility, competence, character and sociability were the most important in establishing and maintaining credibility.
Bias and source credibility Bias plays a complex role in determining source credibility. While bias is often viewed negatively, scholars like Danielle DeRise argue that it must be understood in context. DeRise suggests that bias reflects a source's perspective and is sometimes unavoidable, particularly in opinion-based topics. Warrington highlights strategies for identifying bias, such as analyzing an author’s use of ethos, logos, and pathos. These approaches help readers assess whether bias affects a source’s reliability or contributes valuable context. This understanding of bias is critical for developing a comprehensive evaluation of a source's credibility.
Lateral reading as a critical skill
Lateral Reading is a strategy identified as essential for evaluating the credibility of digital information, as demonstrated by research from Wineburg and McGrew, which highlights its effectiveness in distinguishing reliable sources from misinformation. Unlike traditional "vertical reading," which involves analyzing a single source in isolation, lateral reading encourages users to leave the original source and verify its claims across multiple independent references. Wineburg and McGrew’s research demonstrated that professional fact-checkers excelled in this technique, outperforming students and historians in identifying reliable sources. Their study involved participants verbalizing their thought processes while evaluating live websites, revealing that fact-checkers used lateral reading to cross-check claims across multiple sources, whereas students and historians relied more on vertical reading, focusing on a single source. Carillo and Horning expanded on this by highlighting the strategy's application in educational contexts, where it serves as an effective method for teaching students how to navigate information online. As digital misinformation grows, lateral reading has shown itself as a foundation of media literacy.
Dynamics
Initial credibility is established before a speaker appears before an audience to deliver a particular message. If there are few people in the audience who know the speaker, the level of credibility is at a low, and just the opposite can apply if the speaker is known. The levels are incredibly high with well-known authors, personalities, celebrities, politicians, professors and the like. For instance, the credibility would be incredibly low if a recently published author walked on a stage as opposed to Stephen King gracing the place with his presence. One simply has more of a trust/believable factor than the other.
B.J. Fogg identified initial credibility as surface credibility in his 2003 book Persuasive Technology: Using Computers to Change What We Think and Do. He defined it as credibility that derives from "initial judgments based on surface traits such as a persons' looks, his or her dress, or hairstyle"
The same can be said for advertisements. Generally, people are familiar with Nike, Puma and New Balance. A fairly new shoe company would have to work harder to gain customers. If a person/company is virtually unknown, they must create a sense of trust, believability in themselves and their product. People need to see evidence that the person/company can be trusted. The well-known person/company has to live up to the previous expectations and not disappoint those who have shown up to see them speak and possibly purchase product. The advertising and marketing industry calls this brand management.
Transactional credibility is based on what takes place after initial credibility is established and during the course of interaction. Several factors affect credibility at this stage. How the audience receives the speaker's message, if the speaker will make a new or reaffirm old impressions, and how the speaker conveys his/her confidence or lack thereof are just a few. These factors could affect credibility either way for the speaker and affect how well the speaker's message is received. Either consciously or subconsciously, the audience examines the speaker's competence, likeability, passion, character, and, depending on the environment of the interaction, professionalism. Recent research by Wineburg and McGrew (2019) emphasizes the importance of 'lateral reading', a method where evaluators leave a source to verify its claims using multiple external references. This technique has proven to be effective in identifying bias and uncovering alternative motives, especially in interactions where initial judgments may need revision based on additional evidence. To maintain credibility, the speaker should be knowledgeable about the subject, sincere in his/her approach, enthusiastic and even relaxed. All of this will make the audience lean more towards trusting and having faith in the speaker rather than the opposite. In this sense, the audience comes with an expectation and hopes to leave with a better feeling about themselves as it relates to the person, product and/or company.
Terminal credibility refers to what the audience takes away with them once the interaction has concluded. If the audience felt the speaker had good dimensions of source credibility, the terminal credibility will be high. On the other hand, if the speaker was incompetent, lacked character, did not maintain composure, and came off as unsociable and introverted, the terminal credibility will be low. This final form of credibility hinges on how the audience perceives the speaker and if the speaker uses valid information to get specific points across to those listening. Terminal credibility in one interaction will affect initial credibility in the next.