廣告訊息之理解與說服效果：捷思式－－系統式訊息處理觀點

Comprehension and Persuasion on Advertising Message: Heuristic-Systematic Model Approach

本研究應用「捷思式－－系統式訊息處理途徑模型」之觀點，探討來源可信度與視覺化線索如何影響消費者對廣告訊息的理解與態度，並同時驗證消費者的理解過程是否符合方法目的鏈所述「屬性－－結果－－價值」之結構。研究一結果顯示，消費者在捷思式途徑中會依賴來源可信度作為廣告訊息理解的主要線索，且理解層級符合方法目的鏈所主張的，從屬性到結果到價值的層次。研究二則發現，捷思式－－系統式二元訊息處理途徑中的捷思式與系統式途徑兩者可以並存，當訊息以口語化方式呈現時，消費者主要採取捷思式處理途徑，依賴來源可信度（代言人）作為線索來評估與判斷廣告內容，然而若強化訊息內容的有形線索，則會誘發消費者進行系統式途徑，因而弱化來源可信度的影響力；換言之，視覺化有形線索是有效的調節變數，可用來干擾來源可信度對訊息的理解與態度形成。

For a long history, firms abundantly use different kinds of endorser in advertisements as an information cue or a signal of quality. But still very few researches have been devoted to understand how source credibility can influence the way consumers comprehend advertising messages and evaluate advertised product. It is also not clear whether the persuasion effect of celebrity endorser is always better than non-famous endorser, and in what condition firms can use cheaper non-famous endorser but generate comparable communication effect. In order to answer those questions, this article, through the lens of the heuristic-systematic dual-processing model (HSM), is aimed to research how source credibility and visualization can impact consumer’s comprehension and persuasion of advertising messages, as well as to examine whether the structure of comprehension conforms to the means-end chain (MEC) theory which postulated an “attribute-consequence-value” sequential chain in comprehension of product message. MEC was developed by Gutman in 1982 with the intension to explain how consumers link product attributes to the consumption consequence and then to the value they desired during the process of comprehending adverting message. This theory provided a good tool to measure the communication effect on message comprehension. And Hovland, Janis, and Kelly (1953) assumed that persuasion variables (e.g., source expertise) can influence persuasion by their impact on the causally prior processes of attention and comprehension of message content. So they proposed that comprehension mediates persuasion. On the other hand, the HSM is a persuasion-based model that examines information processing as an antecedent to attitude formation in social judgment (Chaiken, Liberman, and Eagly 1989). When processing information heuristically, message perceivers are said to employ comparably little effort, typically relying on easily accessible information, such as the source’s identity or other non-content cues, in deciding whether or not to accept a message’s conclusion (Chaiken 1980) . This type of processing is more likely to occur with low involvement, low perceived capacity to process information, or when an individual does not perceive more in-depth processing to be of much consequence. On the contrary, systematic processing is defined by effortful exploration and comparison of information. When processing information systematically, perceivers actively attempt to comprehend and evaluate a message’s arguments (Chaiken and Eagly 1983). We can thus infer that the impact of source credibility will be different between heuristic and systematic processing and will be much salient when customers process information heuristically. But how can we induce consumers to engage systematic processing and therefore the impact of source credibility can be weakened? What Mitchell (1986) argued may give us some ideas. Mitchell (1986) demonstrated that the visual component in ads may affect the evaluation of product attributes. Photographs (pictures) often play a major role in persuasion and are evaluated positively, creating more favorable attitudes toward ads and brands. In line with this rationale, we assume that consumers use source credibility as a heuristic cue to comprehend an advertised product’s message, and the “attribute-consequencevalue” chain does exist in the message comprehension process which mediates their attitude toward the ads and the brand. Additionally, based on Motchell’s argument, we proposed that visualization of message may activate the systematic processing in which the persuasion effect of celebrity endorser may be diluted. This research is consisted of 2 experimental studies in which a series of TV type advertisements was created as the stimulus materials, and a credit card of fictitious brand was used as the product. We included undergraduate students from a large university in Taiwan as subjects in both studies and subjects were randomly assigned to one of the experimental conditions. Study 1 was to investigate the structure of comprehension and the effect of source credibility on comprehension and persuasion. We proposed that consumers use source credibility as a heuristic cue to activate their heuristic processing. A one-factor 4-level (source credibility: celebrity/expert/student/employee) between-subjects experiment was conducted. After watching the ads, each participant was asked to report their perception of comprehension and persuasion by answering the questions in a booklet. The intent of Study 2 was to further investigate the effect of visualization on comprehension and persuasion. The hypothesis is that the moderating effect of visualization can provide important information for consumers who are motivated to use heuristic-systematic dual-processing to develop accurate comprehension and attitudes. We used a 4 × 2 factorial between-subjects design. The two factors were source credibility (celebrity/expert/student/employee) and message type (verbalization/visualization). Before watching the ads, participants were asked to report their product knowledge of credit card. The purpose was to activate systematic processing, since it can elicit individuals’ considerably greater cognitive effort and make them focus on specific information. Findings of Study 1 reveal that consumers rely on source credibility in heuristic processing to comprehend a product’s attributes, consequences, and value. And the structure of comprehension indeed consists with what means-end chain theory postulated. But it failed to confirm the mediating role of comprehension on persuasion. Findings of Study 2 show that heuristic and systematic processing can co-occur. When an advertising message is presented by verbalization, consumers are more likely to engage in heuristic processing, relying on source credibility as a heuristic cue to arrive at a judgment. However, when information is presented by visualization, the influence of systematic processing tends to dominate over heuristic processing, and as a result, the effect of source credibility was diluted. These two replicated experiments offer important implications for advertisers. In the case of a tangible and familiar product for the target (e.g., a credit card), it could be essential to provide product-attribute messages to counteract the effects of source credibility heuristic cues. In other words, when the message type is provided for more visual condition, compared with a highcredibility endorser (e.g., a celebrity), a low-credibility endorser (e.g., an employee) may produce commensurate communication effect. Moreover, it could be dramatically cost saving for a company to adopt its own employee or a typical consumer as an endorser.