Construction and validation of a scale to measure celebrity endorsers' perceived expertise, trustworthiness, and attractiveness.

Construction and Validation of a Scale to Measure Celebrity Endorsers' Perceived Expertise, Trustworthiness, and Attractiveness

The purpose of this study was to develop a scale for measuring celebrity endorsers' perceived expertise, trustworthiness, and attractiveness. Accepted psychometric scale-development procedures were followed which rigorously tested a large pool of items for their reliability and validity. Using two exploratory and two confirmatory samples, the current research developed a 15-item semantic differential scale to measure perceived expertise, trustworthiness, and attractiveness. The scale was validated using respondents' self-reported measures of intention to purchase and perception of quality for the products being tested. The resulting scale demonstrated high reliability and validity. Marketing and advertising practitioners share the belief that a communicator's character has a significant effect on the persuasiveness of the message. In testimonial advertising, consumers traditionally have been chosen as product endorsers because of their similarity to target audiences. Although this practice continues, a more noticeable trend appears to be endorsements by actors/actresses, athletes, and other celebrities and well-known athletes, who are closely associated with both the product and the target audience (Business Week 1987; Miller 1989; Morrison 1980; Slinker 1984).

The selection of an appropriate spokesperson for a product or a service is an important, yet difficult, decision. Is an effective and credible spokesperson someone who is attractive, trustworthy, or an expert, or even a combination of all three traits? Is a credible spokesperson an individual who is dynamic, qualified, authoritative, sociable, or safe? Since Aristotle's time (or before), politicians, orators, and public speakers have attempted to identify the determinant qualities of effective speakers (Giffin 1967).

A number of empirical investigations have examined the effectiveness of using credible spokespersons to enhance the persuasiveness of messages. Studies have measured the process by which a communicator's perceived attractiveness, trustworthiness, and expertise mediate immediate and delayed attitude change and persuasion (Anderson and Clevenger 1963; Baker and Churchill, Jr. 1977; Hovland and Weiss 1951; Johnson, Torcivia, and Poprick 1968; Kelman and Hovland 1953; Patzer 1983; Simon, Berkowitz, and Moyer 1970; Whittaker and Meade 1968).

Several researchers in the field of speech communication have utilized factor analytic techniques to uncover the perceptual structure of source credibility (Applbaum and Anatol 1972; Berlo, Lemert, and Mertz 1969; Bowers and Phillips 1967; McCroskey 1966; Whitehead 1968). Their attempts have resulted in the development of scales, each of which includes a different set of dimensions for the measurement of source credibility. For example, Berlo, Lemert, and Mertz (1969) define source credibility as encompassing the dimensions of safety, qualification, and dynamism. On the other hand, McCroskey (1966) identifies authoritativeness and character as other dimensions of source credibility; while Whitehead (1968) identifies objectivity as another dimension of source credibility. In the process of developing scales to measure the effectiveness of celebrity endorsers, a number of researchers in advertising and marketing have expanded the number of dimensions encompassing the source-credibility construct (DeSarbo and Harshman 1985; Simpson and Kahler 1980-81; Wilding and Bauer 1968; Wynn 1987). Table 1 presents a summary of major research studies that have addressed the scaling of source credibility.

Although all the studies were designed to measure the same construct, there is no consistency among the authors as to the number and types of dimensions that source credibility comprises. Furthermore, with the exception of McCroskey (1966), none of the authors have assessed the reliability and validity of the resulting scales. As should be apparent, most attempts to assess the impact of source credibility have been based on instruments of unknown reliability. This fact partially explains the inconsistencies in the literature regarding the impact of communicator credibility as it relates to attitude formation and attitude change. Given the accumulative nature of research, and the fact that researchers base and build the findings of their studies on that of others, there must be a consistent measurement approach for source credibility. This measurement approach first must provide a theoretical basis for the selection of constructs to represent the hypothesized dimensions of source credibility, and second, must produce a valid, reliable measurement scale. In view of the widespread theoretical and empirical interest in the concept of source credibility, the purpose of the present research is to advance and then to assess a tri-component construct using psychometrically accepted procedures to produce a reliable and valid scale.

Definitions of Source Credibility

"Source credibility" is a term commonly used to imply a communicator's positive characteristics that affect the receiver's acceptance of a message. Understanding and defining source credibility in the advertising and speech communication context is often confusing because of the many different operationalizations that appear in the literature. For example, in experimental studies, source credibility is often considered a categorical variable, such that individuals are presented as having high or low credibility (e.g., Anderson and Clevenger 1963; Griffitt 1966; Maddux and Rogers 1980). Other approaches commonly used to describe this phenomenon include the use of such labels as: ethos, prestige, reputation, status, authority, competence, etc. (e.g., Applbaum and Anatol 1972; Giffin 1967; McCroskey 1966).

Research and reflection on the topic of celebrity endorsement rest on two general models: the source-credibility model and the source-attractiveness model. The source-credibility model resulted from a landmark study by Hovland and his associates (1953). They analyzed the factors leading to the perceived credibility of the communicator and concluded that two factors--namely, expertness and trustworthiness--underscore the concept of source credibility. Hovland, Janis, and Kelley (1953) defined expertise as "the extent to which a communicator is perceived to be a source of valid assertions," and …