A Re-Examination of the Relative Persuasiveness of Comparative and Noncomparative Advertising

ABSTRACT - Recent research has demonstrated that relative measures are more sensitive than nonrelative measures which have traditionally been used in assessing comparative advertising effects. This evidence has been offered as a means of explaining the equivalence of direct comparative and noncomparative ads with respect to persuasion, a typical finding of past research. To more fully substantiate the robustness of these findings, the present study re-examines comparative and noncomparative ads previously found to be equivalent in persuasiveness. As expected, the relative measures used in the current investigation revealed greater persuasion engendered by the comparative ad than by the noncomparative ad. Furthermore, the results provide evidence for a biasing effect, in which a relative encoding frame, once activated, may influence the processing of subsequent noncomparative information.

Citation:

Paul W. Miniard, Michael J. Barone, Randall L. Rose, and Kenneth C. Manning (1994) ,"A Re-Examination of the Relative Persuasiveness of Comparative and Noncomparative Advertising", in NA - Advances in Consumer Research Volume 21, eds. Chris T. Allen and Deborah Roedder John, Provo, UT : Association for Consumer Research, Pages: 299-303.

Advances in Consumer Research Volume 21, 1994      Pages 299-303

A RE-EXAMINATION OF THE RELATIVE PERSUASIVENESS OF COMPARATIVE AND NONCOMPARATIVE ADVERTISING

Paul W. Miniard, University of South Carolina

Michael J. Barone, University of South Carolina

Randall L. Rose, University of South Carolina

Kenneth C. Manning, University of South Carolina

ABSTRACT -

Recent research has demonstrated that relative measures are more sensitive than nonrelative measures which have traditionally been used in assessing comparative advertising effects. This evidence has been offered as a means of explaining the equivalence of direct comparative and noncomparative ads with respect to persuasion, a typical finding of past research. To more fully substantiate the robustness of these findings, the present study re-examines comparative and noncomparative ads previously found to be equivalent in persuasiveness. As expected, the relative measures used in the current investigation revealed greater persuasion engendered by the comparative ad than by the noncomparative ad. Furthermore, the results provide evidence for a biasing effect, in which a relative encoding frame, once activated, may influence the processing of subsequent noncomparative information.

INTRODUCTION

Since Wilkie and Farris' (1975) suggestions about the potential persuasion advantages of comparative over noncomparative ads, these two forms of advertising have been pitted against each other in numerous investigations. Although comparative ads have been found to outperform their noncomparative counterparts (Demirdjian 1983; Golden 1979; Gorn and Weinberg 1984; Levine 1976), such findings are the exception rather than the rule. Indeed, in some cases, comparative ads have been found to be less persuasive than noncomparative ads (Grossbart, Muehling, and Kangun 1986; Swinyard 1981). Most often, however, comparative and noncomparative ads are reported to produce very similar levels of persuasion (Belch 1981; Dr÷ge 1989; Golden 1979; Goodwin and Etgar 1980; Gorn and Weinberg 1984; Grossbart et al. 1986; Levine 1976; Sujan and Dekleva 1987; Swinyard 1981).

One response to this diversity in empirical findings has been a search for moderating factors (Iyer 1988; Miniard, Rose, and Till 1992a; Pechmann and Stewart 1990; Shimp and Dyer 1978). Iyer (1988), for instance, observed that comparative ads outperformed noncomparative ads when the advertised brand was unknown, but not when the advertised brand was familiar (see Shimp and Dyer 1978 for similar results). Similarly, Pechmann and Stewart (1990) have considered the moderating role played by the relative market shares of the advertised and comparison brands. They found comparative ads outperformed noncomparative ads when a low-share advertised brand was compared to a high-share brand, while the opposite was true when a high-share advertised brand was compared against a low-share brand. When both the advertised and comparison brands possessed moderate shares, direct comparative and noncomparative ads appeared equal in their persuasiveness.

Researchers have also begun to pay greater attention to the measures used to test for potential persuasion differences between comparative and noncomparative ads. One early indication of the importance of alternative measures in assessing persuasion was provided by Gorn and Weinberg (1984). Although persuasion is typically gauged by responses to various belief, attitudinal, and/or intention measures, Gorn and Weinberg reasoned that one possible outcome of comparative advertising is an enhanced association of the advertised and comparison brands. Based on this rationale, they included measures of the perceived similarity between the advertised and comparison brands. Their results supported comparative advertising's associational effect, which has become one of the more consistent findings in the comparative advertising literature (Dr÷ge and Darmon 1987; Johnson and Horne 1988; Pechmann and Ratneshwar 1991; Sujan and Dekleva 1987).

Recently, Miniard, Rose, Manning, and Barone (1992b) have developed the framing correspondence hypothesis as a means of conceptualizing the role of measurement in tracking comparative advertising effects. In the following section, we briefly review this conceptualization and its implications for measuring comparative advertising effects.

THE FRAMING CORRESPONDENCE HYPOTHESIS

Conceptualization

According to the framing correspondence hypothesis, a measure's sensitivity to advertising effects depends upon the degree of correspondence between the encoding frame used during ad processing and the measure's response frame. One characteristic important to both types of frames is whether they are relative or nonrelative in nature.

Comparative ads presenting claims about the advertised brand relative to one or more competitors are likely to lead to the use of a relative encoding frame during ad processing, in which information about the competitor(s) is used as a point of reference. This reference point becomes an integral part of the encoding frame employed during ad processing, as information about the advertised brand will be encoded relative to that regarding the comparison brand. Consequently, the resulting post-message impressions (e.g., beliefs, attitudes, and intentions) stored in memory are themselves likely to be relative in nature.

In contrast, noncomparative ads lack explicit reference points, in that they present information focusing solely on the advertised brand. Unless consumers spontaneously generate their own reference points, a nonrelative encoding frame is likely to characterize ad processing. [Evidence germane to this supposition is provided in a study conducted by Walker, Swasy, and Rethans (1986), in which only 10% of subjects exposed to a noncomparative ad reported thinking about how the advertised brand compared to a competing brand(s).] As a result, the post-message impressions stored in memory are unlikely to be relative in nature.

Similarly, measures can differ in whether they employ relative or nonrelative response frames (cf. Barnard and Ehrenberg 1990; Teas and Wong 1992). Relative measures require judgments using some specified reference point (e.g., "How likely is it that brand A powdered cleaner is safer and gentler than brand B?") which nonrelative measures lack (e.g., "How likely is it that brand A powdered cleaner is safe and gentle?").

The framing correspondence hypothesis predicts that the most sensitive measures of an ad's effects are those that contain a response frame which corresponds to the encoding frame present during ad processing. Thus, when an ad is processed with a nonrelative encoding frame and the resultant post-message impressions are stored in a nonrelative fashion in memory, nonrelative measures are expected to yield the most sensitive assessment of the ad's effect. However, when a relative encoding frame is used during ad processing, relative measures with response frames that mirror the encoding frame should prove most sensitive.

Correspondence between encoding and response frames is important for at least two reasons. One reason is suggested by Tversky, Sattath, and Slovic's (1988) compatibility principle. A lack of correspondence between the information stored in memory and a response frame will increase the number of mental transformations and, consequently, the number of errors that arise when transforming stored impressions into a form required by the measure. As a result, when the post-message impressions residing in memory are relative in nature, more transformation errors are likely to occur in response to nonrelative measures, and such errors should undermine the accuracy of such measures in capturing advertising effects.

Further support for the framing correspondence hypothesis can be found in the memory literature. According to the principle of encoding specificity (Tulving and Thomson 1973), the retrieval of information encoded during ad processing should be facilitated when aspects of the encoding context (i.e., cues) are present at retrieval. Comparative ads, which encourage a relative encoding frame during ad processing, provide an association between the advertised and comparison brands. This frame can be recreated through the use of relative measures, which provide an external association between the two brands. This external association serves to cue the retrieval of comparatively framed ad information more precisely than nonrelative measures which do not explicitly specify this association.

In sum, the framing correspondence hypothesis posits that the encoding frame present during ad processing directly influences the nature of the resultant mental representation. The encoding frame is thought to be a function of the particular reference point (if any) activated during ad processing. Identification of the relevant frame (and, for relative encodings, the specific reference point as well) is critical in determining a measure's sensitivity to advertising effects, as measures which employ response frames that correspond to the encoding frame used during ad processing should provide the most sensitive assessment of advertising effects.

Empirical Evidence

Most of our work germane to the framing correspondence hypothesis has been within the context of comparative advertising. We observed that one rather common characteristic of research reporting little difference in the persuasiveness of comparative and noncomparative advertising is their use of nonrelative measures. Yet, as suggested by the framing correspondence hypothesis, measures using relative response frames that correspond to the encoding frame activated by a comparative ad should prove most sensitive to the unique effects of comparative ads. Consequently, we have executed a number of studies that tested for persuasion differences between comparative and noncomparative ads using both relative and nonrelative measures (Miniard et al. 1992b, 1993; Rose et al. 1993). This research has shown relative measures consistently outperform nonrelative measures in revealing persuasion differences in favor of comparative advertising.

While our research suggests that the reliance on nonrelative measures may be one reason that prior investigations have often found direct comparative and noncomparative advertising to be equivalent in their persuasiveness, none of our studies employed ads used in prior studies reporting null findings. Rather, new ads which typically featured an unknown advertised brand compared to a well-known brand, a combination that is quite conducive to the emergence of persuasion differences in favor of comparative advertising (Iyer 1988; Shimp and Dyer 1978), were created and tested.

We sought to overcome these limitations in the present study by re-examining comparative and noncomparative ads previously reported to be equivalent in their persuasive effects. As noted earlier in the paper, Pechmann and Stewart (1990) did not detect persuasion differences between a direct comparative ad and a noncomparative ad when the advertised and comparison brands possessed moderate shares. In their study, persuasion was assessed in terms of subjects' responses to the question, "In the future, when you need to buy [product category], which brand do you think you will actually buy?" However, we wondered whether this single indicator of persuasion, operationalized in a manner that does not correspond to the encoding frame of the comparative ad, might provide a very conservative estimate of any potential persuasion differences between their direct comparative and noncomparative ads. Consequently, we retested the ads from one of the two product categories examined by Pechmann and Stewart in their moderate share condition. [We wish to thank Connie Pechmann for providing us with these ads.] We attempted to enhance the odds of detecting persuasion differences by using a set of measures with two important features. First, to maximize the measures' sensitivity to the comparative ad's effects, the measures employed a response frame that corresponded to the encoding frame encouraged by the comparative ad. Second, in addition to asking subjects to choose between the advertised and comparison brands, we also assessed their beliefs, attitudes, and intentions toward the advertised brand relative to the comparison brand. Doing so enabled us to more fully examine the different ways in which advertising may be influential.

METHOD

Subjects and Ads

Sixty-six undergraduate business students were assigned randomly to one of two conditions, in which they were presented with either the noncomparative or direct comparative print ad for Comet brand cleanser used by Pechmann and Stewart (1990). The ads were similar in layout, but differed from one another in several respects. First, the headline in the comparative ad included a reference to a comparison brand, Ajax. Also, the first attribute claim in the comparative ad described Comet as being safer and gentler on surfaces than Ajax. The headline and first attribute claim in the noncomparative ad, on the other hand, made no references to the Ajax brand. Claims regarding the second and third attributes (cleaning ability and use on many surfaces) were noncomparative in nature in both the comparative and noncomparative ads.

Procedure

Subjects were informed that they would be shown an ad for a brand of powdered cleanser. They were also instructed to evaluate the advertised brand with the expectation that, following ad exposure, they would answer questions regarding their impressions of the advertised brand and make a choice between different brands of powdered cleansers. To this end, subjects were presented with two folders, the first of which contained the experimental ad. Subjects were allowed to examine this ad for as long as they wished, after which they were to complete a questionnaire included in the second folder. Subjects were instructed to answer the questions without referring back to the ad.

TABLE

MEANS AND SIGNIFICANCE TESTS

Measures

With the exception of a dichotomous choice measure, in which subjects made a choice between Comet and Ajax, all measures employed 9-point response scales. These measures were relative in nature, in that they required subjects to make judgments regarding Comet relative to the comparison brand, Ajax. For example, beliefs regarding the first attribute were assessed through the use of a likelihood measure which asked subjects, "How likely is it that Comet is safer and gentler on surfaces than Ajax?" Similar measures were used to assess subjects' beliefs with respect to the remaining two attributes (cleaning ability and use on many surfaces). Subjects were also asked to indicate their perceptions of the overall quality of Comet compared to Ajax on a scale anchored by "very low" and "very high." Subjects' attitudes towards Comet relative to Ajax were then assessed using the average value (r = .98) of two scales, one with the endpoints of "more unfavorable" and "more favorable," and the other, "more negative" and "more positive." Lastly, subjects indicated their intentions to purchase Comet compared to Ajax.

RESULTS

The Table summarizes the cell means and significance tests for the relative measures. Mean differences between ad conditions were tested using one-way analysis of variance (df = 1,64).

Consistent with our earlier findings (Miniard et al. 1992b, 1993; Rose et al. 1993), the current results support the usefulness of assessing comparative advertising effects with correspondent relative measures. As can be seen in the Table, subjects reported significantly (p<.05) more favorable beliefs about the advertised brand relative to comparison brand for two (i.e., "safeness/gentleness" and "use on many surfaces") of the three featured attributes following exposure to the comparative ad. Similarly, the comparative ad produced significantly (p<.05) more favorable attitudes toward the advertised brand relative to the comparison brand. Relative purchase intentions were also more favorable toward the advertised brand in the comparative ad condition (p<.1). Surprisingly, responses to the overall quality measure, although directionally consistent with the responses to the other measures, did not statistically differ across the ad conditions (p>.1).

Further evidence of the comparative ad's persuasive superiority was provided by the choice measure. When asked to choose between the advertised and comparison brand, a greater percentage of subjects chose the advertised brand in the comparative (97%) than the noncomparative (80%) ad condition (c²(1) = 4.54; p<.05).

DISCUSSION

Although our prior research has suggested that one reason for null findings in the comparative advertising literature was the failure to employ correspondent relative measures, this evidence is limited by its failure to retest the same comparative and noncomparative ads used in published studies reporting no differences in the ads' persuasive effects. To overcome this limitation, we re-examined ads from Pechmann and Stewart's (1990) moderate share condition. These ads were also attractive because they featured a well-known advertised brand, unlike the fictitious advertised brand typically used in the ads examined in our earlier investigations. As such, Pechmann and Stewart's ads afforded a more stringent test of potential persuasion differences by virtue of having to change pre-existing attitudes toward the well-known advertised brand rather than simply influence attitude formation, as in the case of an unknown advertised brand (Iyer 1988; Shimp and Dyer 1978). [Nearly 85% of the subjects reported having previously used the advertised brand, thus indicating that the vast majority of subjects entered the study with pre-existing attitudes toward the advertised brand based on prior consumption experience.]

The present findings reinforce our earlier findings. By using persuasion measures with response frames that corresponded to the encoding frame encouraged by the comparative ad, we observed significant persuasion differences between the comparative and noncomparative ads. In particular, the comparative ad produced more favorable beliefs, attitudes, and purchase intentions. And when asked to choose between the advertised and comparison brands, more subjects selected the advertised brand following exposure to the comparative ad.

Although we used ads from Pechmann and Stewart's (1990) moderate share condition, self-reported usage data suggest that the advertised and comparison brands featured in these ads were not moderate share brands for the subjects participating in our research. Nearly two-thirds of the subjects reported being current users of the advertised brand, whereas only 15% indicated that they currently use the comparison brand. These relative usage levels are much more in alignment with Pechmann and Stewart's (1990) high-share advertised brand and low-share comparison brand condition.

Interestingly, it has been suggested (Pechmann and Stewart 1990) that high-share brands should rely on noncomparative ads rather than comparative messages in order to avoid potential problems associated with the latter (e.g., providing free advertising for the comparison brand, increasing awareness of the comparison brand, upgrading the comparison brand's image). However, published empirical evidence germane to this situation is limited to Pechmann and Stewart's (1990) findings of noncomparative ads being more persuasive than comparative ads for high-share advertised brands. In contrast, our findings imply just the opposite, at least within the confines of our study. If both patterns of effects prove robust, future efforts might focus on understanding when each type of advertising might be most effective for high-share brands.

There is another aspect of our findings which we believe is worth emphasizing. Although only the initial attribute claim in the comparative ad described the advertised brand as superior to the comparison brand, a significant effect was observed for the third and final attribute claim (use on many surfaces). Subjects were more likely to perceive the advertised brand as superior to the comparison brand on this attribute after processing the comparative ad, even though the ad did not make any reference to the brand's relative performance on this feature. Perhaps subjects inferred that the absence of harsh abrasives (discussed in the ad as substantiation for the claim involving the safe and gentle attribute) would enable the product to be used on a greater number of surfaces. Whatever the reason, this result in itself is suggestive of the potential for relative encoding frames, once activated, to alter subsequent processing of even noncomparative information. Such findings should be particularly important to public policy officials, since it indicates the possibility for misleading consumers about the relative performance of competing brands even in the absence of any overtly deceptive ad claims.

It is also interesting that this apparent biasing effect of a relative encoding frame was limited to the third featured attribute and did not extend to the second attribute presented in a noncomparative fashion within the ad. The fact that this effect occurred for one attribute but not the other implies that the impact of a relative encoding frame on the processing of noncomparative claims may be moderated by certain factors. Future research may wish to further explore when comparative ads containing noncomparative claims may lead to biased processing.

Limitations

One potential threat to the meaningfulness of our findings is whether they are driven by a demand artifact. Specifically, subjects in the comparative ad condition might infer that the experimenter wants them to perceive the advertised brand as superior to the comparison brand. This inference should become particularly salient when responding to the relative measures. Thus, the persuasion differences suggested by the relative measures may simply reflect subjects' willingness to comply with presumed experimenter expectations rather than the actual impact of the ads themselves.

Although certainly plausible, the pattern of effects observed in our study seem rather incompatible with a demand explanation. In particular, it is not obvious why a demand effect would lead subjects to provide responses that differ significantly for some, but not all, of the relative measures. Presumably, a demand effect, once operative, should alter subjects' responses to all of the measures. Further evidence germane to this demand explanation can be found in Rose et al. (1993).

A more clear-cut limitation of our study is the sole reliance on relative measures. Unlike our earlier investigations, we did not include nonrelative measures to serve as a benchmark. Unknown, then, is how the relative measures' performance would compare to nonrelative measures. By the same token, it would have been desirable to have included the particular measure used by Pechmann and Stewart (1990) in assessing advertising effects. Lacking this, it is impossible to determine whether the different effects observed in their study and our study are due to differences in how persuasion was measured versus the other factors (e.g., subject population, exposure condition, etc.) along which the two studies differed from each other.

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