Effects of Product Class Knowledge on the Evaluation of Comparative Versus Noncomparative Messages

Angelina Villarreal-Camacho, San Diego State University
ABSTRACT - This study proposes prior knowledge as one of the moderating factors that limit the effectiveness of comparative advertising. Comparative and noncomparative messages including objective information about a complex product were shown to individuals with varying product class knowledge. Results show that prior knowledge has a positive influence on the evaluation of and preference for comparative messages and on the evaluation of the sponsoring brand. This indicates that the greater the product class knowledge, the more likely to prefer comparative over noncomparative messages.
[ to cite ]:
Angelina Villarreal-Camacho (1985) ,"Effects of Product Class Knowledge on the Evaluation of Comparative Versus Noncomparative Messages", in NA - Advances in Consumer Research Volume 12, eds. Elizabeth C. Hirschman and Moris B. Holbrook, Provo, UT : Association for Consumer Research, Pages: 504-509.

Advances in Consumer Research Volume 12, 1985      Pages 504-509


Angelina Villarreal-Camacho, San Diego State University


This study proposes prior knowledge as one of the moderating factors that limit the effectiveness of comparative advertising. Comparative and noncomparative messages including objective information about a complex product were shown to individuals with varying product class knowledge. Results show that prior knowledge has a positive influence on the evaluation of and preference for comparative messages and on the evaluation of the sponsoring brand. This indicates that the greater the product class knowledge, the more likely to prefer comparative over noncomparative messages.


Studies reveal the amount of product class knowledge individuals possess plays an important role in acquiring and using information. Cognitive psychologists, for example, report differences in problem solving ( Chi 1981), information use (Fiske and Kinder 1980), and comprehension and recall (Bransford (1972) among individuals with varying degrees of knowledge. Consumer behaviorists, on the other hand, have investigated the effects of product class knowledge on information -integration (Park 1976), information retention (Alba 1983, Gartner 1983), information use (Gardner 1983), and organization of information in memory (Hutchinson 1983, Mitchell et. al. 1983) . Their results also report differences in the processing and use of information among consumers who possess varying knowledge of a specific product class.

In spite of the important role prior knowledge has on processing information, few studies have investigated its influence on the perception and evaluation of advertisements, a communication vehicle used (among other purposes) to provide consumers with product information.

The purpose of this study is to investigate the role product class knowledge has on the evaluation of messages which differ in amount, type, and complexity of information. In particular, the effectiveness of comparative versus noncomparative messages among expert and nonexpert consumers is addressed in this paper.

Prior Knowledge and Advertising Effectiveness

It is generally acknowledged that consumers' prior knowledge influences their reaction to persuasive communication. The same advertisement may or may not be perceived as complete, interesting or useful depending on the consumers' currently activated knowledge; however, research in this area is scant. There are few studies that have used advertisements as the stimuli for testing hypotheses regarding the influence of prior knowledge on the processing and acquisition of information. In one study it was found that product attribute based information advertising is more likely to be attended to and interpreted by highly knowledgeable individuals (Edell and Mitchell 1978). This study also reports that individuals with little product class knowledge generated significantly fewer counterarguments than the more knowledgeable subjects.

Research on the impact of technical wording on advertising found that consumers' responses to complex information are influenced by their prior experience with the product class and their education level (Anderson and Jolson 1980). The authors suggest that knowledge influences the interpretation and comprehension of the message. Marks and Olson (1981) studied the impact of knowledge on cognitive responses elicited by advertisements. They found that high knowledge reduced the number of cognitive responses, especially counterarguments. Highly knowledgeable individuals displayed more positive attitudes toward the advertised brand which they were more likely to recommend. Marks and Olson suggest that knowledge improves message acceptance by providing the consumer with an appropriate framework to evaluate the message.

In a study designed to test the role of prior knowledge in the acquisition, retention, and use of new information, Srull (1983) employed four experimental situations. An advertisement was used in only one experiment, in which Srull manipulated subjects' moods and prior familiarity. His results show that under high familiarity, moods (positive, negative, or neutral) do not influence how subjects encode the information provided by the advertisement but under low familiarity, moods influence the rating provided. Subjects in a positive mood rated the product more positively than subjects in a neutral or in a negative mood. Product evaluation, on the other hand, did not differ as a function of prior familiarity when neutral moods were induced. Srull suggests that under high familiarity, subjects are resistant to mood influences while under low familiarity, mood has a strong effect on product evaluations.

Alba (1983) also tested the effects of product knowledge on the comprehension, retention, and evaluation of product information. His results show that while knowledge did not affect reading time, it did account for differences in quantity and content of recall. High-knowledge individuals recalled more complex information and more idea units (e.g . sentences) than low-knowledge individuals.

From the amount of research in @ b area, it is impossible to derive conclusions on the influence of prior knowledge on advertising effectiveness, however, it is obvious that prior knowledge does affect message comprehension and retention.


Since 1971 when the Federal Trade Commission issued guidelines encouraging advertisers to name competing brands as a means to improve the consumers' information environment, there has been a substantial increase in the use and specificity of comparative claims. This increase in the use of comparative advertising has been accompanied by empirical studies examining the effectiveness of this form of advertising, particularly with respect to the effects of comparative versus noncomparative messages.

Most research has followed the definition proposed by Wilkie and Farris (1975) who defined comparative advertising as a message that: (1) compares two or more specifically named or recognizably presented brands of the same generic product/service, and (2) compares specific attributes. Several researchers have taken a broader perspective by incorporating implicit comparisons and nonproduct based attributes (McDougall 1977; Sewall and Goldstein 1979).

Overall, research on comparative advertising has produced mixed results. Levine (1976) and Pride et al. (1977) reported no favorable effects of comparative advertising on awareness levels. Jain and Hackelman (1978) found that the advantage on brand recall for comparative messages lasted no more than one day. Notwithstanding, Prasad (1976), found higher recall with comparative messages than with noncomparative messages, however, his study used indirect rather than direct comparisons.

Concerning attitude formation and change, results are scant. Wilson (1976) reported that subjects exposed to comparative messages indicated a greater willingness to change their views toward the product, than subjects exposed to noncomparative messages. Goodwin and Etgar (1980) indicate that although comparative advertising improves (only marginally) consumers' feelings toward the advertisement, it does not improve respondents' attitudes toward the promoted brand.

Behavioral responses to comparative messages have been measured by buying intentions and actual purchase behavior. The findings reported by several researchers indicate no significant differences in buying intentions between consumers exposed to comparative messages and consumers exposed to noncomparative messages (Belch 1981; Golden- 1976, 1979; Levine 1976; Shimp and Dyer 1978).

Several researchers have focused on the consumers' perceptions of comparative versus noncomparative messages. Wilson (1976) found that comparative messages were perceived as less believable and more offensive than noncomparative messages. Levine (1976) and Shimp and Dyer (1978) also found that comparative messages were perceived as lower in believability. Golden (1979), conversely, found no significant difference in perceived believability between comparative and noncomparative messages. Claim credibility has also been researched. Golden (1979) found no significant differences on the credibility of claims between comparative and noncomparative messages. Swinyard (1981) and Wilson and Muderrisoglu (1979) found that consumers perceived comparative messages as lower in credibility when compared to noncomparative messages. Opponents to comparative advertising have used these results to suggest that the use of comparisons in a message leads to deceptive or misleading information.

Although the FTC encouraged the use of comparative messages as a way to improve the consumers' information environment, research has found no significant differences between comparative and noncomparative advertising in terms of perceived usefulness of the information provided by the message (Golden 1979; McDougall 1977; Pride et al. 1977; Shimp and Dyer 1978; Wilson 1976). Furthermore, skepticism toward advertisers who use comparative messages was found in several studies (Golden 1979; Shimp and Dyer 1978; Wilson 1976). Belch (1981) suggested that dislike of advertisements that explicitly compares products may motivate consumers to rely on disparagement of the advertiser as a strategy for processing comparative messages. Also,subjects exposed to comparative messages generated more source derogations than those receiving noncomparative messages. Swinyard (1981) and Wilson (1976) also found more negative ideation in response to comparative versus noncomparative massages.

Message and respondent characteristics moderate perceptions and evaluations of comparative messages. Prasad (1976) discovered that perceived credibility ratings were lower among individuals with prior preference for the comparison brand. McDougall (1978) found that users of the comparison brand were less receptive to comparative claims than respondents who were loyal to other brands or uncommitted. Pride et al. (1977) found that comparisons that were moderate in intensity showed more favorable results than those that were strong in intensity, particularly among owners of the comparison bran 1. Brand loyalty and product usage rate measures were also used in studies by Etgar and Goodwin (1978, 1980) and by Belch (1981), however, they did not show any significant effects on dependent measures when used as covariants.

Several studies have examined the effects of one and two sided messages in a comparative message context. Swinyard (1981) found that credibility of comparative messages can be increased through the use of a two-sided claim. Etgar and Goodwin (1978) found that a two-sided comparative advertisement was superior on product-related measures, but inferior with regard to ad-related perceptual measures. Mazis (1976) found some positive effects for two-sided comparative appeals on cognitive response measures, but not for attitudes and purchase intention. Belch (1981) found no significant differences in one- and two-sided comparative messages even after multiple exposures to the ads. The relative effectiveness of comparative messages is influenced by several other factors such as advertising theme (Golden 1979), competitive or market position of the advertiser (Shimp and Dyer 1978; Golden 1979), and claim substantiation (McDougall 1978; Golden 1979).

In summary, despite the extensive amount of research on comparative advertising, results are diverse. Comparative messages are not more effective than noncomparative ads with respect to attitude and purchase intention. There is evidence that consumers perceive comparative messages more negatively and have more negative thoughts toward them than toward noncomparative advertisement.

Furthermore, the effectiveness of a comparative message may be influenced by both message and recipient factors. Factors such as claim substantiation, message sidedness, market position, and ad theme may moderate the effects of the message as may prior knowledge and initial predispositions of the recipient. Additional research of specific conditions in which a comparative messages are effective (i.e. under high familiarity, under high involvement, etc.) should provide better insights.


The results on the impact of prior knowledge on message acceptance indicate that the amount of prior information individuals have of a particular product class affect their attention and their ability to comprehend, recall, and evaluate the information presented in the message.

Although prior knowledge has not been addressed in previous research as one of the recipient characteristics that may affect the effectiveness of comparative messages, the complexity of this type of message may require some prior experience with the product class to understand how the similarities/dissimilarities between the brands affect the performance of the sponsoring brand. The recipient of a comparative message is required to understand how the compared attributes affect product performance and why the combination presented provide the best results. Empirical evidence in Cognitive Psychology suggests that prior knowledge helps individuals to distinguish important product attributes and thereby focus their attention on the most relevant product characteristics (McArthur 1980). Prior knowledge also increases the ability to understand and remember a complex message (Bransford 1979; Bransford and Johnson 1912, 1973). Finally, prior knowledge influences recall of information and facilitates the processing of the information (Spilich et al . 1979, and Chiesi et. al. 1979)

Research on prior knowledge using an advertisement or a similar communication as a context, suggests that knowledge influences the information processing of a message, therefore, it plays an important role in its evaluation. This may be particularly important in the context of comparative advertisement given the type of information provided. In particular, it is suggested that:

H1 High knowledgeable individuals will react more favorably (advertiser, advertisement, and brand evaluations as well as purchase intention) to comparative messages than to noncomparative messages; and,

H2 Low knowledgeable individuals will react more favorably (advertiser, advertisement, and brand evaluations as well as purchase intention) to noncomparative messages than to comparative messages.


A pretest/posttest laboratory experiment tested the research hypotheses. A 2x2 between-subjects design was used with type of message (comparative or noncomparative) and product class knowledge (high or low) as the factors. Printed messages for a new brand of personal computer to be introduced into the U. S. market were produced to serve as message stimuli. The new brand, unknown in the U. S. market, was selected to avoid any possible confounding effects due to prior liking or disliking of the brand.

Also, comparative messages are often used for new products to compare them with market leaders. The decision to use personal computers as product class was based on the results of a pretest which indicate that consumers prefer comparative messages of complex products with several objective characteristics that can be compared. Similarly a new and complex product permits manipulation of the amount of prior knowledge a consumer has.

One comparative and one noncomparative full-color printed messages were designed for this study. The decision concerning which attributes to include was based on pretesting numerous personal computers' attributes. Special features of a personal computer not commonly found in the computers sold in the U. S. market were chosen as the main appeal of the message.

The comparative message used in the experiment compared three brands on nine attributes. The noncomparative one presented the same information but just for the sponsoring brand. The messages were constructed alike. The same background, picture, colors, headings, introductory sentences and message layout was used.


Members of seven computer clubs in a large East Coast city participated in this study. All the participants had interest in personal computers, however, their knowledge of the product class varied. Some were nearly experts in the field while the majority desired to know more about personal computers. Of the 200 subjects contacted, just 75 had the characteristics desired (either high or low product class knowledge).

Pretest: Knowledge Manipulation

The purpose of pretesting the experiment was to measure the participant's product class knowledge.

Knowledge was measured by three different concepts: knowledge about product attributes, knowledge about brands available in the market, and experience with the product class. Knowledge about product attributes was measured by using a "paper and pencil" test in which individuals were asked to name the concept applied to a list of the definitions. Knowledge about brands was measured by using a recognition test in which fifteen computer brand names were mixed with fifteen noncomputer brand names. Experience with the product class was measured by the number of hours during a week spent in front of a personal computer, and by the type of computer usage. Eleven different usage categories were developed ranging from computer games (the simplest) to software development (the most complex).

After completing the pretest, correlations between the measures used were calculated. Concept identification, brand identification, and usage type were highly correlated. Time showed low correlation and was found to be high among subjects who used the computer to play games or for word processing. These results indicate that is the quality of time ( usage type) and not the amount of time what makes a difference between high and low knowledgeable individuals.

A three-way classification method using the three measures was used to identify high and low knowledgeable subjects. Seventy-five individuals were selected to participate in the second phase of the experiment. Thirty-nine subjects were categorized as high in knowledge and thirty-six subjects were categorized as low in knowledge.

Dependent Measures

Message reactions were measured by using semantic differential scales that measured advertiser evaluations (biased-unbiased; believable-unbelievable; sincere-insincere), advertisement evaluations (favorable-unfavorable; interesting-boring; attractive-unattractive; useful-useless), brand evaluations (positive-negative; favorable-unfavorable), information search intention (likely-unlikely; wise-foolish) and purchase intention (likely-unlikely).

Posttest Procedure

Members of each group (high or low knowledge) were randomly assigned to the comparative and noncomparative experimental conditions. Each participant received a booklet containing either a comparative or a noncomparative message and a questionnaire. The booklets instructed participants to read the advertisement and answer questions. In addition to the five dependent measures used (advertised evaluations, advertisement evaluations, brand evaluations, information search retention and purchase retention), self-perceived familiarity with the product class and demographic characteristics were also measured after at exposure.


Manipulation Check

To determine whether the individual's knowledge manipulation was successful, during the posttest subjects were asked to evaluate themselves in three dimensions: (1) knowledge about the important features of personal computers, (2) knowledge about computer alternatives and their performance, and (3) overall knowledge about personal computers. A seven-point scale was used to measure these perceptions. The results of these manipulation checks (in Table 1) suggest that the knowledge measures used to divide the sample into two groups were successful.


High Versus Low Knowledge Individuals

Self perception of knowledge were different between these two groups. While the differences are clear with respect to product features and overall knowledge, the differences between available brands, although significant, are not extreme, therefore, the term "high knowledge" refers to an individual with an extensive knowledge about product features and available brands, and the term "low knowledge" refers to those with limited knowledge about product features. Also, it is important to note that in this research, individuals without computer knowledge were not included. All the participants, by club membership, by ownership, by work experience, or by mass-media exposure were previously exposed to personal computers.

High Knowledge and Comparative Ads

The first hypothesis concerns the effects of high product class knowledge on the message acceptance measures used. With respect to advertiser evaluations, results indicate that individuals with high product class knowledge perceive comparative messages as more believable (X-3.45) than noncomparative messages (X-4.70). No differences were found with respect to the perception of biasedness or sincerity of comparative and noncomparative ads. Refer to Table 2.


Among highly knowledgeable participants, a comparative advertisement was perceived as more favorable (X-3.63) more interesting (X-4.16) more attractive (X-3.05) and more useful (X-3.58) than a not comparative at (refer to Table 2). Also the sponsoring brand was more favorably perceived (X-3.27) and more positively evaluated (X-3.61) (Refer to Table 25.

As a result of exposure to a comparative ad, highly knowledgeable individuals showed higher information search intention: likely (X=4.19) and wise (X=4 .37), however, no significant differences in purchase intention was found among high knowledge individuals exposed to comparative or noncomparative ads. The results presented above partially support the first hypothesis. Individuals with high knowledge provided higher advertisement evaluations, brand evaluations, and information search intention where they are exposed to comparative messages, however, no significant differences in advertiser evaluations and purchase intention were fount.

Low Knowledge and Noncomparative Ads.

The second hypothesis refers to the effects of low product class knowledge on the message acceptance measures used . Among this group (low product class knowledge) comparative ads were perceived as more believable (X-4.70) than noncomparative ads (X=5.44). No significant differences were found in terms of biasedness and sincerity. Refer to Table 2.

Advertising evaluations were also higher for comparative ads. Low knowledgeable participants evaluated comparative ads as more favorable (X=4.10), more interesting (X=3.20), and more attractive (X=3.40) than noncomparative ads. No significant difference in the usefulness of comparative versus noncomparative ads was found. Refer to Table 2. Brand evaluations were higher when a noncomparative message was used. The sponsoring brand was more favorable (X=4.52) and positive (X=4.13) when presented in a noncomparative advertisement than when presented in a comparative advertisement. Information search intentions were also higher as a result of exposure to a noncomparative message (likely: X=4.47; wise: X=4.92). No significant difference in purchase intention was found between comparative and noncomparative advertisements. Refer to Table 2.

The results suggest that individuals with low knowledge provide higher brand evaluations and information search intention when exposed to a noncomparative advertisement. However, they provide higher advertiser and advertisement evaluations when exposed to a comparative advertisement.

Knowledge and Type of Message

To examine the relationship between the amount of knowledge (high versus low) and the type of message (comparative versus noncomparative) the dimensions of each of the message reactions measures were factor analyzed to derive five summary measures: advertiser evaluation, advertisement evaluation, brand evaluation, purchase intention, and information search intention. Anova was used to analyze the data. The results are shown in Table 3. The results confirm the previous analysis. Amount of knowledge influences brand evaluations and information search intentions, however, it does not affect advertiser evaluation, advertisement evaluation. and Purchase intention.



Comparative advertising is a controversial issue in advertising research. The results reported in this study suggest that knowledge may be one of the many moderating factors that limit the effectiveness of comparative messages. Prior knowledge seems to influence brand evaluations and information search intentions. The higher the knowledge the more positive the brand evaluations and the more likely the recipient of a comparative ad will engage in more external information search about the sponsoring brand.

In this study evaluations of comparative advertisements were surprisingly more positive than evaluations of noncomparative advertisements. The brand used in the study has very unique characteristics not found in the available brand, therefore, a comparison that points out this uniqueness may be viewed more positively than a comparison that focuses on more simple differences.

The impact of prior knowledge should be further explored before drawing definite conclusions on the impact of prior knowledge on the effectiveness of comparative versus noncomparative messages. Knowledge was manipulated at two levels, high and moderate-low. A more complete understanding of the role of prior knowledge can be gained if several types of knowledge (high, moderate, low, no knowledge) and several types of product (convenience, comparison, specialty; or high and low involvement) are included in the research situation.

Overall, the findings suggest that knowledge has a definite influence on effects of advertising.


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