Several studies, in the past few years, have demonstrated that eWOM review credibility is a basic requirement for the adoption of the eWOM message (Lis, 2013). Indeed, according to the author, the more the recipient perceives the message as credible, the greater is the chance that the message information will be adopted and used. This is the reason why it is crucial, in order to understand the effects of eWOM reviews on the purchase decision process, to gain a better understanding of all of the determinants which lead the review to be perceived as credible by the reader. The literature so far has focused the attention on several aspects – determinants – that are integrated in the model proposed in Figure 1.

Chih et al. (2012) point out that consumers, when looking for online reviews, satisfy two basic needs: a functional need and a social need. The former is addressed through obtaining buying-related information, whereas the latter through what Chih et al. (2012) call social orientation through information. The same logic has been confirmed by Cheung et al. (2009), who categorise credibility determinants in informational and normative determinants. According to Cheung et al. (2009): “[i]nformational influence arises from information obtained as evidence about reality. It is based on the receiver’s self-judgement of the received information ... Normative influence, on the other hand, refers to the influence on the individual arising from the norms/expectations of others that are implicit or explicit in the choice preference of the group or community” (p. 13).

Informational Determinants

Informational determinants include argument strength, recommendation framing, source style, source credibility, and confirmation to prior belief.

- Argument Strength: It is also referred to as argument quality (Teng et al., 2014). According to Teng et al. (2014), quality comprises the strength of the argument, its comprehensiveness, accuracy, timeliness, and relevance. If the review content is perceived as valid from the recipient, then a positive attitude toward the product/service will be developed, and the argument will be perceived as credible.

- Recommendation Framing: Recommendation framing stands from the valence of the review (Cheung et al., 2009). Indeed the review can be positively and/or negatively structured. Previous studies have demonstrated that, generally, negatively framed messages are perceived from the receivers as stronger: a phenomenon also called negative bias (King et al., 2014) (Cheung and Thadani, 2012). According to King et al. (2014), this is more evident when receivers have a neutral opinion toward the review topic. Two possible reasons why the negative bias occur are, according to Cheung et al. (2009), that receivers are sure that negative messages are not uploaded by marketers or companies’ personnel, and that people tendency is to avoid taking risks. Teng et al. (2014) add that a negative valence results in a growth in sales, since allows the receivers to become more confident and understand better the product.

- Source style: Source style stands for all of the visual text and visual cues that can stimulate the information elaboration, and that can increase the information retention (Teng et al., 2014). Teng et al. (2014) assert that the quantity of information reduces the risk perceived, while the volume of reviews affects users’ acceptance of the information. King et al. (2014) add that the length of the text has an influence on the helpfulness perceived. Another salient characteristic of source style is recommendation sidedness (Cheung et al., 2009). In general, messages are classifies as one-sided if they include either positive or negative features, while two-sided if they include both. Concerning perceived eWOM credibility, two-sided messages are more complete, enhancing in this way the quality of the review, which in turn tends to be perceived as more credible (Cheung et al., 2009). When analysing source style, it is also important to look at the content. King et al. (2014) show that, for feature-based products, it is essential to provide more information to enhance the credibility of the review, while, for experiential goods, the subjective point of view it is more relevant. It is necessary to specify that nowadays, most of the time, products are a combination of features and experiences.

- Source Credibility: Source credibility can be defined as all of the characteristics of the communication source perceived by the receiver (Lis, 2013). According to Ohanian (1990,91 cited in Lis, 2013), the credibility of the source is built upon three main characteristics: expertise, trustworthiness, and homophily. Source expertise includes the knowledge, skills and experience of the source (Lis, 2013). Teng et al. (2014), define experience as to which extent the source is familiar with the product related to the review. The greater the expertise, the more likely the review will be perceived as credible (Lis, 2013). On the other hand, trustworthiness represents the degree of objectivity and sincerity perceived in the review (Lis, 2013). In an online context, it is hard for the receiver to assess this parameter, so indirect methods such as consistence of the arguments or objectivity of the content are adopted in order to evaluate it (Lis, 2013). According to the scholar, source trustworthiness is positively associated with eWOM review credibility. Finally, homophily, also referred to as “like-me principle” or “source attractiveness”, stands for the degree of similarity between the participants, in terms of demographic determinants or shared values and experiences (Lis, 2013). Teng et al. (2014) explain that the receiver perceives the source as appealing based on the degree of similarity, familiarity (i.e. level of comfort), and likeability (i.e. personal traits and physical appearance), even though the latter is absent online, due to eWOM anonymity. The higher the resemblance among the participants, the higher the likelihood that the review will be perceived as credible (Lis, 2013).

- Confirmation to prior belief: When the receivers read the review, they tend to perceive it as credible if the information included is consistent with their prior knowledge and expectations (Cheung et al., 2009). The concept is related to what King et al. (2014) refer to as confirmation bias, which stems from people tendency to look for affirmative evidences supporting their thoughts and choices.

Normative Determinants

Every time the information on position favoured by others is accessible to the eWOM recipient, normative determinants occur, influencing the perceived credibility (Cheung, 2009). According to Cheung et al. (2009), there are two main normative determinants: recommendation consistency, and recommendation rating.

- Recommendation Consistency: The extent to which the current recommendation is consistent with the other messages already posted by other contributors, makes the review more or less credible (Cheung et al., 2009). This effect is enhanced online, since generally it is a space where it is easy to compare different comments. According to Cheung et al. (2009), if the review is consistent with the others, it will be more likely perceived as credible, whereas if it is not, the receiver will be confused, and the degree of perceived credibility will be lowered.

- Recommendation Rating: Recommendation rating represents the overall rating given by other receivers on the same recommendation (Cheung et al., 2009). The authors demonstrate the significance of this determinant on the level of perceived eWOM review credibility.

Asch (1951 cited in Cheung et al., 2009) in his study points out how, in traditional communication, normative determinants lead only to public compliance, but not necessarily to a change in the private personal opinion. However, Cheung et al. (2009) demonstrate that, in eWOM, Asch results cannot be applied, and that normative determinants seem to influence also the private opinion.

Web Reputation

Web reputation is a determinant introduced by Chih et al. (2012), in order to explain the effect that the web site reputation can have toward the perception of the eWOM review credibility. The scholars have demonstrated through their research that a strong reputation of the platform can lead to a higher perceived credibility. This phenomenon cannot be included either in informational or normative determinants since reputation is a complex concept, which seems to result from both an individual and collective thinking.

Moderators

Different authors, through their research, have demonstrated that the credibility determinants afore mentioned can be strengthened of weakened by several moderators in eWOM. The model provided in Figure 1., embraces the most relevant factors which act as moderators when it comes to the perceived credibility. Motivation, ability, and involvement will be taken into consideration.

- Motivation: Hoyer and MacInnis define motivation as “an inner state of arousal that denotes energy to achieve a goal” (2001 cited in Cheung et al., 2009).

- Ability: Ability denotes having the necessary resources in order to make an outcome happen (Cheung et al., 2009). The most important factor concerning ability, according to Cheung et al. (2009), is prior knowledge that can be further classified in prior knowledge of the review topic and prior knowledge of the online platform. The research results of Cheung et al. (2009) point out that different type of prior knowledge can impact on different determinants. In particular, the research states that a higher prior knowledge of the topic leads source credibility to be less relevant in determining eWOM review credibility, whereas a higher prior knowledge of the online platform makes recommendation rating to be considered more, as what it seems to be a heuristic shortcut adopted by the receiver.

- Involvement: According to Lis (2013), involvement is determined by the relevance of the object, in terms of needs, values, and interests of the receiver. Lis (2013) point out that, in eWOM, high involvement leads the reader to process the source attributes in a better way. In other words, high involvement strengthens expertise and homophily effects. On the other hand, according to Lis (2013), trustworthiness effect seems to be weakened with high involvement. Together with trustworthiness, also recommendation rating is weakened in situations characterised by high involvement (Lis, 2013).

CONCLUSION

eWOM is becoming more and more relevant, in a world characterised by empowered consumers who can share, connect and collaborate each other 24 hours a day, 7 days a week (Hanna et al., 2011). The most important characteristics of eWOM, compared to the traditional WOM, have been presented in order to contextualise the research. Several studies, in the past few years, have demonstrated that perceived eWOM review credibility is a basic requirement for the adoption of the eWOM message (Lis, 2013). Consequently, the most relevant determinants of credibility in eWOM communication have been presented. In particular, they can be classified in two broad categories, informational and normative determinants. The research contributes providing a new model which summarises the most relevant determinants uncovered by scholars in this field. The studies conducted until now has focused mostly on written eWOM. Thus, a further contribution would be investigating review credibility related to the more recent forms of eWOM, such as visual eWOM, characterised by a communication based on pictures and videos. Moreover, the researchers should verify if there are other determinants involved in the process, and if the ones already uncovered can be applied in such a context.

MANAGERIAL IMPLICATIONS

Understanding the determinants that enable the review to be perceived as credible, can lead the company to implement strategic decisions. For instance, in a context characterised by high involvement, the company should encourage the consumers with more expertise, or the ones who resemble the most the target group, to create reviews online about the products/services the company sells. Even though the consumers create the content, the company has the opportunity to influence them, building strategies upon the determinants, and establishing competitive advantage.

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