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Home arrow Engineering arrow Measuring Electronic Word-of-Mouth Effectiveness: Developing and Applying the eWOM Trust Scale

Reviewer Credibility

Credibility has been explored from three distinct perspectives: (1) source credibility; (2) message (content) credibility; and (3) medium credibility. Among these, source credibility has been researched most extensively (Yang, 2007). The researchers’ interest is due to the general assumption that a highly credible source is commonly found to induce more persuasion than a low-credibility one (Pornpitakpan, 2004b). Source credibility is a term typically used to suggest that a communicator’s positive characteristics can increase the value of information conveyed in a message and this, as a consequence, affects the likelihood that the receiver subsequently accepts the message (Anderson, 1971; Dou, Walden, Lee & Lee, 2012; Hovland et al., 1953). Source credibility refers to a message recipient’s perception of the credibility of a message source, reflecting however nothing about the message itself (Chaiken, 1980). A landmark among these attempts is surely the contribution of Hovland et al. (1953), who postulate that credibility is a critical attribute associated with the communicator which exerts influence on a recipient’s message acceptance. The authors identify expertise and trustworthiness as the two outstanding determinants of source credibility. Subsequent research increased the confidence in this conceptualization as it regularly identifies the same two dimensions. For example, Ohanian (1990) as well as Pornpitakpan (2004) both conclude that these dimensions are seen as the most important source characteristics. Similarly, Dholakia and Sternthal (1977) find that expertise and trustworthiness determine source credibility. Expertise is defined as the extent the communicator is regarded as representing a source of valid assertions and has the ability to provide accurate information coming from the knowledge, experience, training or skills that the source possesses (Hovland et al. 1953). On the other hand, trustworthiness (here best understood as a synonym for the source’s integrity/honesty) refers to the receiver’s confidence or belief that the source will provide information that is both unbiased and honest (Ohanian, 1991). Hovland et al. (1953) provide evidence that a source’s trustworthiness significantly affects the acceptance of a message and enhances changes in opinions and attitudes. Accordingly, McGinnies and Ward (1980) conclude that communicators who are in the possession of these characteristics cause the greatest change in others’ opinions. In a similar vein, Petty and Cacioppo (1986) define source credibility as the extent to which the information source is assumed to be believable, competent, and trustworthy by the information recipients.

In marketing research, source credibility has been studied mainly in the context of endorser and advertiser credibility. Research on endorser credibility is to a large extent influenced by the source credibility model advanced by Hovland and his colleagues (1953). Therefore, it comes as no surprise that this literature string has also identified trustworthiness and expertise as the most critical elements of a communicator’s credibility. This is also supported by a recent metaanalytic study by Amos et al. (2008), who have found in their study that these two components bear more influence on the effectiveness of ads than any other source characteristics, including celebrity performance and celebrity/product match. This further supports a multi-dimensional understanding of the concept of source credibility. Ohanian (1990) introduces source attractiveness as an additional dimension, which is defined as the receiver’s affection for the source due to its physical appearance and behaviour. Endorser credibility is typically measured with semantic differential items. For instance, expertise is often measured in terms of “knowledgeable-unknowledgeable”, “qualified-unqualified”, and “experienced-

inexperienced”. In contrast, for measuring a source’s trustworthiness, researchers often use terms like “trustworthy-untrustworthy”, “honest-dishonest”, and dependable-undependable” and for attractiveness “beautiful-ugly”, “attractive-unattractive”, and “plain-elegant” (Lafferty & Goldsmith, 1999; Ohanian, 1990).

Another literature string puts its emphasis on the credibility of the advertiser who produced the advertised product being a valuable source of information, i.e., advertiser credibility (Lafferty & Goldsmith, 1999; MacKenzie & Lutz, 1989; Newell & Goldsmith, 2001). Here, in the same tradition, expertise and trustworthiness have been identified as components of credibility. While expertise is generally described as the extent to which consumers have the perception that the company/advertiser has the knowledge or skill to fulfil its stated claims, trustworthiness is defined in terms of whether the company can be trusted to tell the truth or not (Newell & Goldsmith, 2001). Van de Berge et al. (1981) propose that an advertiser’s credibility is best described in terms of trustworthiness, prestige, competence, familiarity, competitiveness along with the affective elements of attractiveness and likeability. Similarly, Haley (1996) found that consumers perceive advertisers as credible when they show adequate levels of trustworthiness, expertise, and attractiveness.

Research on the credibility of individuals who state their opinions and comments online (i.e., reviewer credibility) heavily draws from the traditional view of source credibility. It is commonly understood as a consumer’s attitude towards the message source (Gunther, 1992), which dictates how much the consumer believes in the message sender and consequently the message itself. When a source is perceived to be credible, the level of belief in what the source claims is positively influenced Ling & Liu, 2008; Wu & Wang, 2011). In an analogy, this thesis views reviewer credibility as an (situational) antecedent of eWOM trust. If a consumer holds a positive orientation towards the credibility of eWOM endorsers, he/she will be more likely to trust the information provided by this group of fellow shoppers.

The work of Hovland et al. (1953) seems to be most influential, as reviewer source credibility is recognized as an important factor impacting persuasion effectiveness. Additionally, most researchers recognize that the source’s trustworthiness as well as expertise are both factors that have been most frequently studied. For instance, the works of Brown et al. (2007), Huang et al. (2006), and Luo et al. (2013) all agree that source credibility of online reviewers depends on these two factors. By drawing on the work of Sternthal et al. (1978), Luo et al. (2013) equally define the construct with its dimensions, as they state that source credibility is an information reader’s perception of the expertise and trustworthiness of a source. Consequently, the construct has been regularly measured by applying the semantic-differential scale derived from Ohanian (1990, 1991). For example, Dou et al. (2012) use “dependable-undependable”, “honest- dishonest”, “reliable-unreliable”, “sincere-insincere”, and “trustworthy-untrustworthy” to measure trustworthiness, and “expert-not expert”, “experienced-inexperienced”,

“knowledgeable-unknowledgeable”, “qualified-unqualified”, and “skilled-unskilled” to quantify the expertise dimension. Wu et al. (2001) recognize that source attractiveness is also an important determinant. However, they refrain from measuring this dimension, because according to their opinion eWOM senders cannot be directly contacted by the consumer and therefore attractiveness cannot be assessed. Each of the remaining dimensions includes five semantic-differential items adopted from Ohanian (1990). Similarly, Rabjohn et al. (2008) measure trustworthiness and expertise with two items each. By applying a Likert scale, Lis (2013) quantifies reviewer expertise with five items (e.g., “The reviewer is an expert.”, “The reviewer is qualified.”), and the same amount of items for measuring reviewer trustworthiness (e.g., “The reviewer is honest.”, “The reviewer is sincere.”). All these measures are taken again from Ohanian (1991).

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