Part One: Characteristics of Sources

Elaboration Likelihood Model.  No single theory can lay out a roadmap to a successful communication campaign. So before digging deeply into source selection and use, let’s take a brief return trip to theories relevant for many of McGuire’s inputs. First, we will review the Elaboration Likelihood Model (ELM), a dual process of persuasion paradigm developed by Petty and Cacioppo 4 decades ago; and second, Witte’s Expanded Parallel Processing Model (EPPM), which delves more deeply into characteristics of sources that will be more likely to lead to high elaboration and management of fear and threat messages. The ELM posits that there are two approaches to attitude (and inferentially, behavioral) change: the ‘central’ route or ‘peripheral’ route.  (In this course we generally refer to these as the ‘light’ and ‘heat’ of a message, as Aristotle would have labeled, logos and pathos, respectively).  The central route represents an individual objectively processing information via his or her knowledge and experience, using these to look at different sides of an issue and deciding which is more logical. The peripheral route, in contrast, comprises the processing of incidental cues not necessarily related to a logical, thought-through choice. Such actions are more likely to be emotional or otherwise subjective. The amount of thought elicited by a message is referred to as "elaboration." Higher degrees of elaboration are more likely to lead to and sustain attitude and behavior change. The ELM argues that when a person encounters some form of communication, he or she can process this communication with varying levels of thought (elaboration), ranging from a low degree (low elaboration) to a high degree of thought (high elaboration).

How does the ELM apply to the selection of an ideal source for health behavior change? An effective source of communication may change attitudes and behavior either directly or peripherally. LeBron James, for example, could sell athletic gear through advertisements, appealing to the logical aspects of decision making (e.g., “I’m LeBron James, and shoes made by XYZ Inc. are the best out there”). Alternatively, youngsters who are excited by watching Mr. James play basketball and cheer him on may take note of the XYZ gear that he is wearing, and may be peripherally influenced to buy the same brand of gear.


Politicians routinely appeal to both logic and emotions in their speeches when running for office. To central processors, they will talk up their qualifications and accomplishments, matching these to the office they seek. Not wanting to miss an opportunity to elicit peripheral processing, however, they may also brag about their patriotism, make derisive jokes about or even vilify their opponents, appeal to the anger and fear their audience may have about what would happen if the opponent were elected, expound on how ‘outsiders’ are harming the country, etc. (Note for example, the different talking points used recently by Democratic presidential candidates Elizabeth Warren and Kamala Harris).  Indeed, the centrally processed light of political messages at times takes a back seat to the peripheral heat.

Revisiting McGuire's Inputs. Getting back to McGuire’s Communication-Persuasion framework, the source of a communication is its sender: the person(s), entity (group, agency, political party, hospital, etc.), or idea (e.g., “Black Lives Matter”) that the audience associates with the message. (The Source is the only one of McGuire’s inputs that some pieces do not include, although this is rarely the case).

Credible sources can increase the impact of communication, whereas sources who lack credibility may detract from even the most well designed message. Sources are often experts (e.g. physicians), celebrities, advocates (for various political and social causes) or lay individuals and peers. With respect to sources in general, but especially the lay person/peer category, Rice and Atkin (1979) assert that the source of the communication generally should be similar to the target audience in terms of race, gender, and other important characteristics. This sense of shared identification may indeed be as or even more important than the apparent competence, experience or credentials of the sender of the communication. For example, it may be more important for an African-American woman to see a television spot or poster in which the source of the communications depicted as a peer (i.e., another African-American woman) rather than an authoritative person (e.g., a physician who is neither African-American nor necessarily female) (Nimmo, 1979). For example, examine the use of diversity among the pediatrician sources in Jimmy Kimmel’s piece on childhood vaccinations. Although all would be perceived as experts, different segments of the audience may identify with one or two of these physicians more than with the others.

Another example of taking advantage of shared identity and perceived similarity is in the use of The Muppets to promote healthy eating among kids, though Muppets of course look nothing like human children, nor do they share their experiences. Yet these famous TV characters are meant to speak and act as kids and thus connect with this audience as a credible source—or as paired with a real human source, as in this example.  In other cases, however, having a shared common experience not only is a desirable attribute of a source of communication, it is essential. For example, the “Buddy Check on 22” initiative was launched by a Marine Corps veteran to prevent suicide among other veterans.

Research Activity 1

Compare and contrast “Buddy Check on 22” with this more general Facebook page in terms of source characteristics and their connection to an adience or audience segment.

In terms of Witte’s Extended Parallel Processing Model used to project the effectiveness of fear messages, sources who are similar to or even peers of the target audience may change the audience’s sense of susceptibility to or severity of the threat, and may improve their self-efficacy (competence to perform the tasks needed to address a challenge) and response efficacy (confidence that the action will reduce or eliminate the threat)

Research Activity 2

Find communication pieces on either side of the “Medicare for all” policy struggle where the source(s) seeks to establish a common identity with target audience voters in terms of shared values, expected benefits, etc. 

Part Two: Channels and Sources


​Channels, Sources, or Both? Nearly a half century ago Marshall McLuhan declared that “the medium is the message” (stress added), which became accepted wisdom in the field of mass communication. The medium itself may be seen as a source and have attributes of credibility in the minds of audience members. (This applies as well to outlets or programs within a medium, for example, the New York Times and National Enquirer within print journalism, or Fox News and The Daily Show within TV/broadcast media). Commercial media themselves recognize this phenomenon and may imbed product marketing within their standard news or other material. (See John Oliver’s amusing take on this subject in his HBO show Last Week Tonight). In many cases, the source and the medium are one and the same: physician counseling, public speaking, and peer-led substance abuse treatment are examples. Thus, we are examining sources both in this and the ‘Channels’ modules.

Research Activity 3

Identify a single news outlet, program or comedy that uses a news format that you have occasion to access. Point out aspects of that program that are relatively more and less credible. What contributes to your distinction between the two? Does this influence your decision to view the program?

Part Three: Dimensions of Source Credibility


Source credibility research has a long and varied tradition that is central to the field of communications. Citing research by Berlo and colleagues (1969), McCroskey (1966) and others, the NIH delineate six of the more established dimensions of sources that make them seem more or less credible to the audience. For our purposes, these may be relabeled and reduced to:

1) Character (e.g. friendly/unfriendly, honest/dishonest, virtuous/sinful, just/unjust, and biased/unbiased, which overlaps with…)

2) Intellect (informed/uninformed, intelligent/unintelligent, etc.).

3) Qualifications (experienced/inexperienced, skilled/unskilled, trained/not trained) and;

4) Behavioral style (dynamic/not dynamic, meek/aggressive, energetic/tired, etc.).


Related to source character issues are perceptions as to whether the senders have their own (and even hidden) agendas and stand to benefit by persuading the audience, or conversely, seem to have the audience’s needs foremost on their minds.

Analysis Activity 1

Compare the following 3 pieces regarding gun control. Who are the sources and what are their characteristics? What audiences would perceive them to be credible or not credible, and why?) (Piece 1, piece 2, piece 3)

Research Activity 4

Consider two health communication messages that have helped change your behavior or lifestyle. What aspects of the sources of these messages contributed to their impact on you?

Part Four: Peers, Authorities and Celebrities


Peer or other sources sharing status and values with the audience often function as role models for individuals in that audience. In Albert Bandura’s landmark work Behavior Modification (1969), he shows that observational learning is one of the most important impacts of modeling. (The power of role modeling and imitation is itself the subject of health communication efforts, as seen in this example.)  However, it may not just be new behaviors that are learned, but inhibitions or dis-inhibitions of previously learned behaviors and response facilitation (in other words, previously established behaviors are suppressed or reemerge, respectively). The implication here for selecting sources in health communication is twofold. First, we will want to ensure that the healthy behavior in which our source engages in is met with favorable consequences. Second, however, individuals may feel that role models can engage in risky behaviors and not face any such consequences. If that is the case, we want to ensure that our sources are individuals who have indeed taken unnecessary and unhealthy risks and have paid the price for them. Therefore, the impact of peer models is heavily related to an individual’s developmental stage, with younger children being far more susceptible to the impact of a model, whether it be in learning a new response or having a previous one facilitated, while older adults may have less of a need to learn specifically from role models but may be looking for other issues related to a source of communication. In any case, children will model their behavior after individual peers whom they perceived to be competent rather than incompetent.

Traditionally, communicators and marketers alike have relied on (real or perceived) experts and authoritative figures (qualified, intellectual, or both) to promote social, health, and consumer behavior, as in this infamous series of Lucky Strike cigarette ads from the mid-20th century. Much of the field of health communication began with research into patient-doctor communication in a clinic or hospital setting. Physicians and allied health professionals have a responsibility of distilling complex information about wellness, risk, treatment, and end-of-life options in ways that are understandable and acceptable. This communication has gone far beyond the clinical encounter, with providers using a range of channels (see ‘Channel’ module) including social and broadcast media or patient navigators and community health workers. These all may extend the reach and comprehensibility of their communication. Community health workers in turn may be seen as a lay expert or even peer of the target audience, thus combining some of the advantages of peer and authoritative sources. In Everett Rogers’ Diffusion of Innovations terms, these individuals are often early adopters of a target behavior or practice, and may be used to influence later adopters.

An example of when an authoritative figure may be more effective than a peer would be in a disease outbreak. When actions need to be taken immediately (e.g., risk reduction in Ebola or Zika epidemics, or evacuation during a flood or wildfire), it may be far less important that an individual identifies with the source than that the source knows or seems to know what he or she is talking about and has the resources and knowledge to contribute to immediate protection. Conversely, social issues such as acceptance of new neighbors in a diverse community may require communication from both peer and authoritative sources, as individuals will want to know how others similar to them react interpersonally, yet at the same time may seek an expert’s knowledge on a particular subject.

Sources of communication are often experts (or are portrayed as such; as noted above, physicians were used to promote cigarette brands until the 1950s). But sources may also be simply others who share an experience or have overcome a challenge. In the latter case, the goal of the communication is to promote behavior change and risk reduction through observational learning (i.e., modeling, imitation, etc.). Observational learning strategies can employ either coping or mastery models, the former representing models who are going through the same experience as the audience, and the latter those who have mastered a given skill or overcome risk or illness. (Bandura, 1989). It should be noted, however, that the similarity of a role model is a perception that the audience may have rather than necessarily an objective comparison per se. For example, young people may perceive individuals with athletic skill to be very similar to them, even though objectively they themselves may not have any such skill. The implication of this for health communication is that socially-related behaviors, such as partying in groups, may be more subject to identification with peers and others who are similar than are medically-specific behaviors such as taking prescribed medications on schedule and throughout the prescribed regimen.

Finally, entertainment, sports, and other highly visible celebrities are often used as implied or primary sources (see below) for promoting health or commercial products. There are many advantages to this strategy, the primary one being that audiences may quickly identify with and greatly admire the celebrity. However, celebrities may be difficult to contact or expensive to contract with. Further, as has been the case with Jared Fogle featured on Subway ads and various causes promoted by Lance Armstrong and others, the cause, product, or behavior being promoted may actually suffer when the celebrity’s reputation is tarnished. Therefore, as with the use of any source, the selection of a celebrity must be done with care, and the choice revisited on a regular basis.​

Analysis Activity 2

Examine this DUI ad featuring actress Helen Mirren. Is this an appropriate choice of source? How much credibility does this ad have, and why?

Part Five: How Sources are Presented


Sources may be central or peripheral to the message, and may be expressed (i.e., openly presented) or implied. Medical experts, peers, or others involved in face-to-face communication comprise sources who are central to messages, while billboards mentioning their sponsor in small letters at the bottom are making their source peripheral. Primary and secondary sources may be used as well, with the primary source seeming to deliver the message while the secondary source is possibly its sponsor and is mentioned peripherally. Expressed sources are clearly linked to messages, while other health communication pieces may imply (sometimes falsely) but not state what the source of a message is.

The Brand as the Source

Finally, “branding” is the process of repeatedly pairing messages with images, slogans, tunes or logos until the brand itself serves as the express or implied source of the message. Popular and well-recognized brands will vary substantially from region to region. Branding is explored in detail in the 'Messages' module.

Identifying the "Best" Source

As with all of health communication and social marketing, “beauty is in the eye of the beholder”: through formative research (see ‘Audience’ module), let the audience and audience segments tell you who would best present your health communication messages.

Analysis Activity 3

The widely copied and parodied “I’m not a doctor but I play one on TV” ad originated using the star of the soap opera General Hospital 35 years ago. Examine the health product ad that launched this phrase into common popular use. What are the central and peripheral (primary and secondary), and expressed and implied features of this ad?

Research Activity 5

Identify a health communication, social marketing or standard marketing piece that uses a source that appears to be inappropriate to the apparent purpose of the message. Why was this a poor choice, and what other choice might be better for reaching the audience?


Berlo, D. K., Lemert, J. B., & Mertz, R. J. (1969). Dimensions for Evaluating the Acceptability of Message Sources. Public Opinion Quarterly, 33(4), 563-576.

D. Nimmo editor communication Yearbook three New Brunswick New Jersey: transaction books, 1979, 655 – 68

Witte, 1992

Mccroskey, J. C. (1966). Scales for the Measurement Of Ethos. Speech Monographs, 33(1), 65.