Division of Research November 1985 Graduate School of Business Administration The University of Michigan A CONCEPTUAL AND METHODOLOGICAL FRAMEWORK FOR COMPARATIVE ADVERTISING RESEARCH Working Paper No. 447 David A. Home and Michael D. Johnson The University of Michigan FOR DISCUSSION PURPOSES ONLY None of this material is to be quoted or reproduced without the expressed permission of the Division of Research

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AUTHORS' NOTE David A. Horne is Visiting Assistant Professor of Marketing and Michael D. Johnson is Assistant Professor of Marketing, both at the University of Michigan's Graduate School of Business Administration. The author's gratefully acknowledge the work of Kenneth Shields in helping to develop and conduct the pilot study described in the paper. 1

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INTRODUCTION Explicit comparative advertising is a fairly recent phenomena. Driven by an undeclared change in a vague, regulatory posture (Federal Trade Commission circa 1971) rather than conceptual or theoretical developments, comparative advertising now accounts for a very significant share of advertising expenditures. When the FTC began encouraging direct comparisons in advertising, it saw three basic advantages. First, comparative advertising would make the marketplace of commercial ideas self correcting. Any false claims could be explicitly refuted by competitors and, as a result, the government's role in policing deceptive ads would diminish. Second, the FTC felt comparative advertising would be very informative due to the existence of attribute-by-attribute comparisons. Consumers, as a result, would make better choices based on more information. Third, comparative ads were seen as a means of encouraging competition. If an advertisement showed a particular firm as less capable, more expensive, or otherwise inferior, the affected firm would have an incentive to "straighten itself out" and come roaring back into the fray. The consumer again would benefit as consumption alternatives would generally improve as successive rounds of comparative ads were unveiled. Unfortunately, these are often not the intentions of most advertisers. From an advertising viewpoint, using a comparative ad campaign is more complex. Comparative ads may provoke retaliation in both the marketplace and the courtroom. Also, while advertisers realize that a comparison can give consumers more information, the advertiser's goal is usually one of selective, as opposed to complete, information provision. And because comparative ad campaigns may be better suited for some competitors than others (e.g. a small 2

share or new brand as opposed to a market leader), consumers often end up hearing only one side of the story. The debate regarding the effectiveness of comparative advertising rages on. Unfortunately, and of central importance here, research on the effectiveness of comparative advertising has done little to settle the debate. Interestingly, the often conflicting and generally negative empirical evidence regarding comparative advertising's effectiveness (Lincoln and Samli 1979; Ash and Wee 1983; Shimp and Gresham 1983) hardly dissuades advertising practitioners. The practice is readily apparent in all media for a number of both products and services. Moreover, Hisrich (1983) reports generally favorable perceptions toward and experience with comparative advertising among practitioners. The only conclusion available is that, in spite of substantial research efforts, comparative advertising remains a mystery. Its potential has yet to be determined and, importantly, directions for its use remain elusive. At least in part, this state of affairs stems from two important factors addressed here. First, as is the case with advertising in general, questions exist regarding the validity and usefulness of the test procedures employed by researchers. A variety of research methods have been used across studies, many of which are questionable. It may not be surprising then that nonconvergent results are often the norm. Second, no unified conceptual framework exists regarding the promotional goals of comparative advertising. This has resulted in wide discrepancies regarding how the effectiveness of comparative ads should be measured. In addition, there are no guidelines for designing comparative ads with specific goals in mind. 3

The purpose of this study is to develop and test both a methodological and conceptual framework for the development and testing of comparative advertising in a practical manner. Briefly, our methodological framework calls for an increased use of multiple methods or measurement processes in order to reduce the uncertainty associated with single method studies. Our conceptual framework calls for adherence to both a marketing and related psychological framework for developing comparative ads. According to the framework, comparative advertising's best use may be in accomplishing certain product positioning goals (Wilkie and Farris 1975; Shimp and Dyer 1978; Gorn and Weinberg 1984). With these goals in mind, the development of a psychological framework based on consumer perceptions of proximity is possible which may aid in the construction of comparative ads. We begin by briefly reviewing existing comparative advertising studies and outlining their methodological and conceptual shortcomings. Our methodological and conceptual frameworks are then described in detail. Finally, a pilot study is presented which supports the conceptual framework. METHODOLOGICAL REVIEW Examination of the stream of literature on comparative advertising reveals numerous attempts to make definitive statements regarding its use. Most, however, have failed the test of time and replication (see Lincoln and Samli 1979; Ash and Wee 1983; Shimp and Gresham 1983). Before beginning a methodological critique, the nature and source of the various empirical studies must be mentioned. Several studies either grew into or emerged from doctoral dissertations. Others have been conference proceedings whose only goals were, presumably, to reveal the "tip of the iceberg". The dual shortages of funds and time probably explain a good number of the forthcoming 4

problems. Nonetheless, if billions are being spent in the marketplace, the need for superior research efforts and planning is far from a moot point. We compared the existing empirical studies on four readily apparent factors: 1) the dependent measures employed; 2) the respondents queried; 3) the context surrounding the exposure; and 4) the actual advertisements used. Table 1 presents a chronological listing of the majority of the published empirical studies on the effects of comparative advertising. Not included are conceptual works, reviews, or tangentially related articles. Dependent Measures The initial stage of advertising research, indeed any research, is to precisely define the problem at hand. In the case of comparative advertising, this need for specific and directed focus is critical given the enormous base of possible issues to study (Wilkie and Farris 1975). Progressing from an overall topic to a researchable issue requires the development of dependent variables that clearly tell others what the purpose of the study is and why it is important. As a focus on justified and meaningful measures is critical, we look first at the dependent measures contained in the empirical comparative advertising studies to date. Table 1's list of dependent measures was segmented into three general categories; variables pertaining to the claim, variables pertaining to the brand, and variables pertaining to the sponsor. It should be noted that the descriptive phrases used in the table are as close to the authors' words as possible. There are twenty-four claim variables, nineteen brand variables, and seventeen sponsor variables for a total of sixty different dependent measures in these studies. Even allowing for some misinterpretation of the authors' descriptions, this appears excessive. Closer examination highlights 5

favorites - recall, believability, and informativeness for the claim; intention to buy and recall for the brand. Probably more intriguing is that thirty-seven of the sixty measures were only used once while another thirteen were only used twice. Obviously, cross study comparisons become tenuous when so many different measures are used. In all fairness, there is not much agreement on any advertising effectiveness measure. The studies in Table 1 certainly emphasize that point. Respondent Base The nature of the research population may directly reflect a study's ability to project to the population at large. This basic axiom of non-census research should not require reiteration. Unfortunately it does. The major advantages of using non-probabilistic sampling techniques are, of course, convenience and economy (Selltiz, Wrightsman, and Cook 1976). Non-probability or convenience sampling may also be justified when precise representativeness is not necessary (Babbie 1973). Calder, Phillips, and Tybout (1981), for example, contend that serious attempts to study fundamental mental or cognitive processes are immune to such limitations. A brain, is a brain, is a brain goes the logic. However, advertising is designed to affect different people in different ways. The major problem with using convenience samples, therefore, is that the researcher has no way of evaluating the biases introduced by each group of respondents (Selltiz et al. 1976). In other words, an advertising response, is not an advertising response, is not an advertising response. Table 1's list of the subjects gives as much detail as the authors provided. A glance at Table 1 is alarming. Only Levine (1976), McDougall (1978) and Swinyard (1981) used any sort of random samples. The other 6

fourteen studies used convenience samples, and, of those, thirteen used students. (Shimp and Dyer [1978] used both students and nonstudents.) Of the fourteen respondent sets using convenience samples, nine are known to have used or included business administration students. To put it another way, over half of the respondents in these studies may have been highly sensitized. Notwithstanding the argument that many of the products or services used were often purchased by students, these respondents seem far from typical. Certainly, the student subject debate will continue, but the overwhelming reliance in these instances is startling. Exposure Context While the dangers of reactivity in research are often discussed by researchers, few have so fervently advocated the use of nonreactive or unobtrusive measures as Webb, Campbell, Schwartz, Sechret, and Grove (1981). As their popular example goes, recording floor tile wear at a museum exhibit is a more accurate gauge of popularity than opinion polls. Certainly not all measures or methods can or should be unobtrusive or subtle. However, when the trouble associated with achieving a high quality sample is taken into account, it seems foolish to ignore the possible effects of the research context on the research results. Table 1's list of the study contexts tries to capture the naturalness of the respondents' interaction with the advertisements. It appears that control was an overriding concern of almost every author. Only Swinyard (1981) designed an experiment where he did not know if the respondents "saw" the advertisement. All the others put subjects in unfamiliar surroundings that overtly manipulated their involvement with the advertising. People rarely confront advertisements in such a controlled environment. As a result, the 7

potential for reactive responses due to the overt exposure in the studies is naturally high. The Advertisements Finally, the advertisements themselves are an important criteria for evaluating the methods employed in previous studies. While the issues here are similar to those involved with the reactivity of the research setting discussed above, singular differences emerge. Lifelong exposure to a barrage of professional advertisements has taught the average consumer what an ad should look, sound, and read like. While often necessary given resource constraints, unrealistic ads standout. Table 1's list of the ad's origin is divided into two possibilities - constructed for the study and borrowed from the media. Only Levine (1976), McDougall (1978), Wilson (1980), and Gorn and Weinberg (1984) actually borrowed from the media. The rest were constructed for the study. Certainly, each author did as good a job as possible when constructing the ads. However, subjects can recognize and appreciate professional work, and ads that do not measure up are easily noticed. Once again this may sensitize subjects to the experiments. We now see that the lack of consensus across existing research results is at least partially explained by the variance in research methods or measures used across studies and/or the use of singularly questionable contexts, ads, and respondents. In light of the above discussion, we offer two general methodological suggestions for future research in this area. The first is the need to adopt more multi-method approachs to comparative advertising research. The second is the use of simpler, more straight forward research designs based on clear marketing objectives. 8

METHODOLOGICAL FRAMEWORK Multi-Method Approach A multi-method approach involves the simultaneous use of qualitatively different methods to study the same research hypothesis or proposition. For instance, rather than using only controlled experiments, casual observations, or surveys, two or more such different methods should be combined to study any particular issue. Relying upon any single method implies some sacrificing of internal validity for external validity or vice versa (Campbell and Stanley 1963). A valid test of any hypothesis, therefore, requires the use of more than one method. If one views different methods as different measurement processes, the argument for using multiple methods is the same as that for using multiple measures to study a given proposition. As Webb et. al. (1981, p.35) state, "Once a proposition has been confirmed by two or more independent measurement processes (methods), the uncertainty of its interpretation is greatly reduced.....If a proposition can survive the onslaught of a series of imperfect measures (methods), with all their irrelevant error, confidence should be placed in it." This is not to say that any one method is bad. We are simply saying that the use of any one method, in isolation, does not allow researchers to make conclusions with confidence. Where multiple methods yield consistent results, useful conclusions are possible. Where multiple methods yield differing results, false conclusions are not allowed. In those cases where results differ across methods, it may be possible to trace the difference in results to one particular aspect of one particular study or set of studies. Obviously this will be easier the more incrementally different the methods. 9

While the use of multiple methods sounds ideal, there are obvious practical problems that limit the practice. First is the expense, in time, effort, and money, of doing such extensive research. The resource constraints faced by researchers can severely limit the methods considered. Second is the risk involved with running more than one study and getting discrepant results which, in turn, can prolong the entire process. Research endeavors, which already seem endless, may become extremely lengthy before practical guidelines or conclusions emerge, moreless publications. Nevertheless, very few conclusions can be drawn and put into practice with confidence unless a multimethod approach is taken. Simple Designs A second suggestion is that research on comparative advertising be more straightforward and practical in design. Not only have methodologies varied, but the issues studied, as noted by the range of dependent variables in the studies in Table 1, are also numerous and varied. It was suggested that this lack of focus owes largely to a weak or loosely formulated conceptual framework regarding the promotional objectives of using comparative ads. If the specific promotional goal(s) of a comparative advertisement can be stated clearly, then the need for complicated designs involving a variety of different dependent measures diminishes. If any measure does not directly address achievement of the promotional goals, it is extraneous. Such "extras" only serve to complicate the research design, complicate the respondents' role, and introduce reactivity or demand characteristics. Put quite simply, our proposed framework calls for the use of fewer variables, which are more closely tied to the promotional goals of the advertisement, and more methods or measurement processes to measure attainment 10

of those goals. In the next section a conceptual review is offered followed by a conceptual framework to accompany these methodological suggestions. CONCEPTUAL REVIEW One would hope that a conceptual review results in an orderly progression of useful theoretical explanations. Unfortunately, such a progession is lacking among the available studies. Only three of the empirical studies - Belch (1981), Murphy and Amundsen (1981), and Swinyard (1981) - provide any extensive theoretical justifications. Recall, however, that interest in comparative advertising was driven by a regulatory agency rather than conceptual or theoretical developments. The "rules of the game" had changed, and theory often got lost in the shuffle. Belch (1981) applied a cognitive response approach (Wright 1973) to the use of one-sided versus two-sided comparative advertising messages. He argued that two-sided messages should be more effective that one-sided arguments because counter arguments are less readily available. Moreover, the relatively positive effect of two-sided claims should increase with exposure as the positive thoughts generated have more opportunity to sink in or affect attitudes. Murphy and Amundsen (1981) focused on the issue of new brand utilization of comparative claims using a cognitive dissonance approach. They suggested that consumers ignore or downplay attitude disrupting, or dissonant, information. Because a new brand may claim equality or superiority over more familiar brands, this may be met with resistence or skepticism. Alternatively, however, these authors mention the possibility that new brands may, in fact, encounter fewer negative cognitive respones (using Wright's framework). Because opinions regarding new products have yet to be formed, 11

there is little basis for counterarguing. This idea was suggested originally by Shimp and Dyer (1978). Finally, also in the context of the cognitive response framework, Swinyard (1981) linked active counterarguing to attribution theory. Accordingly, whether or not an advertiser is seen as either truthful or self-serving determines the strength of the counter arguments. While these more conceptually driven studies are in the minority, they do provide a basis for understanding comparative advertising. Nonetheless, the fact that the generally negative research results on comparative advertising are inconsistent with generally positive practitioner attitudes toward its use (Hisrich 1983) suggests that the above mentioned frameworks fall short. Focusing on the underlying purpose of comparative ads may provide the missing link. CONCEPTUAL FRAMEWORK Marketing Goals and Comparative Ads The core of our framework is a central focus on the promotional and related marketing strategy goals that comparative advertising may be used to accomplish. It is important not to start with comparative ads themselves but, rather, with the tactical purpose to which they may be put. In their compelling early conceptual paper, Wilkie and Farris (1975) discussed many of the issues related to comparative advertising and its effects on consumers. From a marketer's perspective, however, the most important of these is the use of comparative ads in accomplishing product positioning goals. As Wilkie and Farris suggest, two possible positioning goals are relevant, association, or using comparative ads to position a product closer to another product or set of products, and differentiation, or using comparative ads to position a 12

product away from other products. Such goals may apply to a new product's initial position or the repositioning of an existing product. Unfortunately, with notable exceptions (see Shimp and Dyer 1978; Pride, Lamb, and Pletcher 1977; Gorn and Weinberg 1984), empirical studies have not focused on these marketing goals. Having a clear statement of the relevant marketing goals allows researchers to choose only specific, relevant dependent measures. When the goal is achieving either an initial or different position, then the perceived position of the relevant products in the minds of consumers is the dependent measure of interest. As is often argued, perceived position should be assessed in a relative fashion, by measuring perceptions for products in relation to their realistic competitors (Wind and Robinson 1972). A direct measure of effectiveness in this case then is the perceived similarity, either overall or on a by attribute basis, of the product in question relative to its competitors. In this light, the use of dependent measures in comparative advertising research is straight forward. Does the comparative advertisement affect the perceived similarity or dissimilarity of the sponsor's product in the desired direction? If perceptual proximity is the psychologically important variable, a look at how consumers judge similarity may also yield insights into how comparative ads should be developed. In the next section of the paper, a psychological model of similarity is described as well as its potential for use in developing comparative ads. A Psychological Model of Similarity Tversky's (1977) contrast model of similarity provides both a model of how similarity judgments are produced and a subsequent framework for 13

developing comparative ads to meet particular positioning goals. For many objects, Tversky views similarity (or dissimilarity) judgments as resulting from a contrasting of the common and distinctive features we associate to those objects. Common features add to similarity while distinctive features detract. The opposite is true for dissimilarity judgments; common features detract from dissimilarity while distinctive features add. Formally, the contrast model appears as follows: s(a,b) = Gf(A nB) - Of(A - B) - pf(B - A) where s(a,b) is the similarity between a and b, the objects of the judgment, and A and B are the feature sets associated with a and b respectively. Similarity is a function of three different types of features, those common to a and b (A (f B), those distinctive to a, (A - B), and those distinctive to b, (B - A). The f function captures the salience of different features within each of these sets (for a more detailed discussion see Tversky 1977). One aspect of the model is particularly pertinent to our discussion and relates directly to the development of comparative ads. The variables 4, PC, and / represent the relative weight, from 0 to 1, of the three different types of features on proximity judgments. The fact that these weights vary from situation to situation explains a variety of contextual effects on perceived similarity. For example, if a pair of products has both many common and many distinctive features, they may be considered both very similar and very dissimilar relative to other product pairs. Johnson (1981), for example, demonstrated how subjects' judgments of similarity among colas, noncolas, and beer are not necessarily negatively related to judgments of dissimilarity. Coke and Pepsi were, for example, considered the most similar pair of colas among subjects judging similarity. Among those subjects judging 14

dissimilarity, Coke and Pepsi were also considered the most dissimilar pair of colas. The contrast model explains such context effects by the weight subjects place on the different feature sets. If the weight in a similarity judgment is more naturally on common features, while the weight in a dissimilarity judgment is more on distinctive features, a pair of products such as Coke and Pepsi, which have both many common and many distinctive features, may be simultaneously considered both very similar and very dissimilar. A second context effect of interest concerns the existence of asymmetries in proximity judgments. When judgments are made in a subject/referent format (i.e. how similar is a to b, where a is the subject and b is the referent), asymmetries often result where a may be more similar to b than b is to a. Asymmetries of this sort have been found among countries, faces, and consumer products (Tversky 1977; Tversky and Gati 1978; Johnson 1981, 1984). For instance, Tversky and Gati found subjects' ratings of the similarity of North Korea to Red China to be greater than the similarity of Red China to North Korea. The contrast model again helps us explain such judgments through the relative weight placed on various feature sets. In a subject/referent judgment, the weight is naturally on the features of the subject. Because Red China has more distinctive features than North Korea, asymmetric judgments may result. Similarly, Johnson (1981) found judgments of the similarity of Shasta Cola to Coke to be larger than judgments of the similarity of Coke to Shasta. Such asymmetries can be traced directly to the greater number of distinctive features consumers associate to Coke (Johnson 1984). When Coke is the subject of a comparison with a product that does not have as many distinctive features, perceptions of similarity will be 15

lower than when Coke is just a referent and its distinctive features are not being emphasized. In light of the contrast model, the positioning goals of comparative advertising can be restated as an attempt to control the weight consumers place on these different feature sets. The advertiser's goal is to emphasize common features when pursuing an association strategy while emphasizing distinctive features when differentiating a product. One very direct way to influence these weights is by taking advantage of subject/referent asymmetries. If any brand with relatively few associated features wants to position itself close to a competitor with many associated features, an effective strategy may be to use that competitor as a referent in a comparative ad. If, alternatively, the goal is one of differentiation, use of the competitor as a subject will highlight everything that is distinctive between the brands. Stating this hypothesis in research form: [H1]: When the products in a comparative ad differ in associated distinctive features, using the product with more distinctive features as a referent in comparison facilitates a strategy of association while using the same product as a subject facilitates differentiation. To summarize, comparative advertising should be viewed as one possible way to achieve product positioning goals. As such, a simple, direct measure of the effectiveness of a comparative ad is its ability to either create or reinforce a certain level of perceived similarity between the sponsor's product and the product or products of comparison. By understanding how proximity judgments are produced in different contexts advertisers may learn how to structure ads to either minimize or maximize perceived similarity. The studies that follow illustrate this process. 16

APPLICATION OF THE CONCEPTUAL FRAMEWORK Pilot Study As an initial test of the conceptual framework, and more specifically, the effect of subject/referent positioning in comparative ads, a pilot study was conducted involving the advertising of a new (hypothetical) cola softdrink named "Sparkle". Four print ads (story boards) were constructed in which Sparkle was compared either implicitly or explicitly with Coke (the pilot study was conducted prior to the introduction of New Coke). Two independent variables were manipulated in the four ads, the subject/referent position of Sparkle and Coke and the expliciteness of the comparison. In all four ads, three characteristics or aspects of the product were given, where Sparkle had half the calories, half the caffeine, and more cola taste than Coke. Objectively, in all four ads Sparkles' attributes place it somewhere in between regular colas (Coke as well as Pepsi and RC) and diet, caffeine free colas (e.g. Diet Caffeine Free Coke, Diet Pepsi Free). If the existence of asymmetric subject/referent perceptions is generalizable to advertising, however, whether Sparkle or Coke are subjects or referents in an ad should result in very different positions. According to the contrast model, because Coke has so many distinctive features (Johnson 1981; 1984), using Coke as a subject in comparison with Sparkle should position Sparkle farther away from Coke (and, perhaps, the other regular colas) than when Coke is used only as a referent. Using Coke as a subject should bring to mind many of Coke's distinctive features while using Coke as a referent should lower the weight consumers place on Coke's features. 17

Two ads were constructed in which the subject/referent comparison was very explicit. In one ad, Sparkle was the subject of the comparison and Coke was the referent. The ad showed a can of Sparkle on the left, a copy line that read "Sparkle, the Cola for You (at the top of the ad)... when Coke is just too much" (at the bottom of the ad). The three attributes were listed just to the right of the can (in the middle of the ad). In the second ad, Coke was the subject and Sparkle was the referent. Two cans were shown, Coke on the left and Sparkle on the right. The copy line here read, "Is Coke too much? (at the top) Sparkle... the Cola for You" (at the bottom). The attribute information was listed in between the cans in the middle of the page. It was believed that the effectiveness of the subject referent manipulation might hinge on the explicitness of the comparison. The more explicitly one uses Coke in the comparison the more likely, perhaps, Cokes distinctive features may come to mind independent of whether Coke is a subject or a referent. Therefore, two more ads were developed using more implicit comparisons. As above, in one ad Sparkle was the subject. Here a can of Sparkle was presented along with the attribute information described above with a short copy line at the top of the ad reading "Less....Yet More". In the second ad, Coke was the subject. A can of Coke was presented at left with the attribute information at right. The copy line at the top read "Too little with too much?" and at the bottom read "Sparkle...Less but More". To test the hypothesis, each ad was shown to a separate group of student subjects in a classroom situation (n= 20, 17, 18, and 22 for the four ads respectively). The ads were shown using a slide projector for one minute. As discussed above, the relevant dependent measure for the marketing manager is 18

the effect of the different ads on the relative position of the new softdrink. After exposure to the ads, subjects in each condition were asked to rate the overall similarity among a group of twelve different cola soft-drinks which included Coke and Sparkle on a seven point scale from 1 (very dissimilar) to 7 (very similar). These judgments were averaged across subjects within groups for analysis. The main hypothesis [H1] is that the similarity of Sparkle to Coke will be higher, or Sparkle will be positioned more closely to Coke, when Sparkle is used as a subject rather than a referent in comparison. The average judgments across the ads support this hypothesis. When Sparkle was the subject, the mean similarities were 3.63 and 3.80 respectively for the explicit and implicit ads. The corresponding figures were 3.17 and 3.31 when Coke was the subject and Sparkle the referent. In order to judge the significance of the results, however, these differences must be viewed relative to the judgments for all the brands in the market. To illustrate the perceived position of Sparkle that resulted from the ads, the similarity judgments among all the colas were analyzed using an additive tree procedure (ADDTREE; Sattath and Tversky 1977) in which the length of the branches in the tree joining different brands represent the perceived distance between the brands. Such an analysis helps determine the particular competitive structure of different markets (i.e. brands on the same branches are more likely competitors than brands on different branches; Urban, Johnson, and Hauser 1984). In hindsight there was little systematic difference across the explicit/implicit versions of the ads. As a result, the similarity judgments were averaged across this condition for the ADDTREE analysis. The resulting trees for Sparkle 19

Subject/Coke-Referent and Coke-Subject/Sparkle Referent ads are shown in Figures A and B respectively (Kruskal's stress values of.061 and.058). The results reveal an important difference in the perceived position of Sparkle in the two conditions which supports the main hypothesis. When Sparkle is the subject of the comparison (Figure A), it is perceptually more competitive with Coke and the other regular colas than when Coke is the focus of the ad (Figure B). Apparently, the Sparkle-Subject ads were more successful in lowering the weight on the distinctive features of Coke than the Coke-Subject ads. This interpretation is also supported by the fact that, in the Coke-Subject ads, Coke and Pepsi are on different branches of the tree while in the Sparkle-Subject ads Coke and Pepsi are on the same branch. SUMMARY AND FUTURE RESEARCH In sum, the subject/referent position of brands in an advertising comparison may have some effect on perceived position. The pilot study results reported here suggest that the hypothesis deserves further research attention. As discussed, one can not make conclusions on the basis of one study. Future research should, therefore, test the effect of subject/referent positions in comparative advertising using a variety of research methods. Such a multimethod approach will have the added benefit of directly testing the validity of several important aspects of existing copy testing methods (e.g. naturalness of exposure to an ad). Overall, this research provides a unified framework for practitioners and researchers interested in comparative advertising. More specifically, the conceptual framework provides guidelines for the construction of comparative ads to meet particular promotional goals. 20

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TABLE I SUMMARY OF COMPARATIVE ADVERTISING STUDIES AUTHOR(S) DEPENDENT VARIABLE(S) SUBJECTS STUDY CONTEXT AD ORIGIN Prasad (1976) Wilson (1976) Levine (1976) Claim - Recall Claim - Believability Brand - Recall Brand - Believability Claim-Informativeness Claim-Believability Cla im-Offens iven ess Claim-Interesting Brand-Ability to Change View Brand-Qualicy Sponsor-Trustworthiness Students (Bus.Admin) Students (Bus.Admin) Femalel (Heads of Household) Laboratory 1 Exposure Booklet-with text and advertisements Laboratory 1 Exposure Booklets - Advertisements only 1 Exposure TV Commercials Constructed for Study Constructed for Study Borrowed from Media Claim Claim Brand Brand Brand - Believability - Clarity - Awareness - Intention to Buy - Important Difference Pride, Lamb, Pl etcher (1977) Sheluga & Jacoby (1978) Claim - Informativeness Claim - Recall Claim - Information Search Claim - Comparison Shop Brand - Recall Brand - Comparison Shop Brand - Information Search Students (Bus.Admin) Students (Psychology) Laboratory 1 Exposure 1 Print Advertisement Laboratory Information Display Board Unlimited Exposure Constructed for Study Constructed for Study Shimp & Dyer (1978) Claim - Claim - Claim - Claim - Claim - Brand - Sponsor Sponsor Brand - Recall Believability Interestingness Informativeness Convincing Purchase Intention - Identity - Truthfulness Attitude Students (High School & College) Social & Community Groups Laboratory Constructed 1 Exposure for Study Booklet - with text and advertisements 22

AUTHOR(S) DEPENDENT VARIABLE(S) SUBJECTS STUDY CONTEXT AD ORIGIN McDougall (a & b) (1978) Claim Claim Brand Brand - Reliability - Helpfulness - Rating - Purchase Intention Female (Random) Laboratory 1 Exposure Printed Messages a)Borrowed from mediatext only b)Constructed for Study Golden (1979) Claim - Believability Claim - Credibility Claim - Information Given Claim - Information Usefulness Brand - Purchase Intention Students (Bus. Admin. & Arts and Science) Laboratory 1 Exposure 1 Written advertisement Constructed for Study Goodwin & Etgar (1980) Claim Claim Claim Claim Claim Claim Claim Claim Claim Brand Brand Brand Brand Brand Brand - Understandability - Impersonality - Useless Information - Irrelevance - Unbelievability - Offensiveness - Attractiveness - Interestingness - Likeability - Knowledge Increase - Better Buy - Perceived Risk - Quality Level - Overall Affect - Intention to Buy Students Laboratory 1 Exposure 1 Written Ad Constructed for Study Wilson & Muderrisoghn (1980) Claim Claim Claim Claim Sponsc Sponsc Sponsc - Counterarguments - Support Arguments - Positive Statements - Negative Statements )r - Derogation >r - Curiosity )r - Neutral - Recall Immediate - Recall Delayed - Decay - Believability - Recall Immediate - Recall Delayed r - Position Students (Bus. Admin.) Students (Bus. Admin.) Laboratory Borrowed 1 Exposure from media Print Advertisement Laboratory Constructed 1 Exposure for Study Booklet with text and advertisements Murphy & Amundsen (1981) Claim Claim Claim Claim Brand Brand Sponsc Belch (1981) Claim - Claim - Brand - Brand - Sponsor Aided Recall Church Unaided Recall Groups Attitude Intention to Purchase - Bias Laboratory 1,3,& 5 Exposures TV Viewing with commercials Constructed for Study 23

AUTHOR(S) DEPENDENT VARIABLE(S) SUBJECTS STUDY CONTEXT AD ORIGIN Belch (1981) (con't) Sponsor Sponsor Sponsor Sponsor Sponsor - Truthfulness - Honesty - Qualification - Believability - Sincerity Swinyard Claim (1981) Claim Claim Brand Brand - Acceptance - Credibility - Counter Arguing - Purchase Intention - Actual Sales with Coupon Random Random Homes Flyer in Doors Unknown exposures Constructed for Study Etgar & Goodwin (1 982) Claim - Claim - Claim - Claim - Claim - Claim - Claim - Claim - Claim - Brand - Brand - Brand - Brand - Brand - Brand - Understandability Impersonality Useless Information Irrelevance Unbelievability Offensiveness Attractiveness Interestingness Likeability Knowledge Increase Better Buy Perceived Risk Quality Level Overall Affect Intention to Buy Students (Bus. Admin.) Laboratory Constructed 1 Exposure for Study 1 Print Advertisement Demirdjian (1983) Tashchian & Slamas (1984) Brand - Actual Purchase with Coupon Claim - Recall Brand - Purchase Intention Sponsor - Friendly Sponsor - Reliable Sponsor - Competent Sponsor - Fair Prices Sponsor - Check Prices Sponsor - Visit Stores Students (Bus. Admin.) Students (Bus. Admin.) Laboratory Constructed 1 Exposure for Study Booklet - Text with Advertisement Laboratory Constructed 1 Exposure for Study Radio - Advertisements within program Gorn & Weinberg (1984) Brand - Brand - Brand - Perceived Distance Perceived Choices Attitude Students Class Time 1 Exposure Print Advertisement Borrowed from media 24

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