TwO'Sided VersusOne'Sided CelebrityEndorsements: The Impacton AdvertisingEffectiveness andCredibility

Michael A. KaminsMeribeth J. BrandStuart A. HoekeJohn C. Moe

This study examines celebrity endorsements in advertising using a two-sided framework, interms of the inieTnalization ami identi^icarion processes of social influence as discussed b>Keiman (1961). The two-sided execution was designed to increase a viewer's perception ofadvertiser credibility by including a discussion of a limitation of the advertised service. Resultsshou' thai when compared to a traditional one-sided celebrity endorsement, the tao-sidedcommunication elicited significantly higher advertising credibility and ejjectiveness ratings,higher evaluation of the sponsor in terms of perceived ofeTall quality of service, as well as asignificantly greater intention to use the advertised service. These Endings suggest that the use0/ a celebrity appeal in a two-sided form is an effective advertising strategy.

Michael A. Kamins (Ph,D,, New YorkUniversity) is assistant professor. Depart-ment of Marketing, School of BusinessAdministration, University of Southern Cal-ifornia, Los Angeles.

Meribeth J. Brand (MBA, University ofSouthern California) is financial analyst,Trust Company of the West, Los Angeles,

Stuart A. Hoeke (MBA, University ofSouthern California) is president. Apex Ser-vices, Inc., Atlanta, GA,

John C, Moe (MBA, University of South-ern California) is project coordinator, Ma-Guire, Thomas Partners, Santa Monica,CA,

Advertisers regularly pursue strategies designed to attract attention to their com-munication and to distinguish their product from competing products with thehope of influencing purchase. In an ever-competitive world, a premium is placedon an approach which can achieve these objectives. One attempt at such a strategyinvolves the use of a celebrity spokesperson. According to Atkin and Block (1983),there are several reasons why a well-known endorser may be influential. First,such a spokesperson attracts attention to the advertisement in the cluttered streamof messages. In addition, celebrities are traditionally viewed as being highly dy-namic individuals with attractive and likeable qualities. Their credibility and be-lievability, however, remain in question.

The use of celebrity spokespeople has been on the rise (Advertismg Age 1978).A 1975 Gallup and Robinson study (reported by Forkan 1975) estimated that 15percent of prime time television commercials featured celebrities. By 1978, thenumber was reported to be over 20 percent. According to a recent report, in-dividuals in the advertising field were said to agree that celebrities are being soughtout to endorse products as never before (Sherman 1985). Given this increase inuse, research on celebrity endorsements becomes increasingly important to ad-vertisers. This is especially true since past empirical research has shown celebritiesto be well liked and oftentimes attractive, though not always credible and effectivespokespeople (Atkin and Block 1983; Freiden 1984; Friedman, Termini and Wash-ington 1977).

Purpose

This research examines celebrity endorsements that utilize a two-sided format inwhich the celebrity spokesperson makes both positive and negative statementsregarding the advertised product. This format is designed to enhance both ce-lebrity effectiveness and overall advertising effectiveness by increasing perceivedcredibility. This two-sided format is compared to the more traditional one-sidedformat where only positive claims are made about the product by a celebrity.

©Journal of AdvertisingVolume 18, Number 2, 1989, Pages 4-10

Background

A celebrity is defined as "an individualwho is known to the public (i.e., actor,sports figure, entertainer, etc.) for hisor her achievements in areas other thanthat ofthe product class endorsed" (cf.,Friedman and Friedman 1979). Al-though previous studies have foundthese individuals to be likeable and/orattractive, these favorable perceptionshave not consistently carried over toenhance measures of believability andpurchase intention.

Friedman and Friedman (1979) foundempirical evidence that, in the pro-motion of products high in psycholog-ical and/or social risk, use of a celebrityendorser would lead to greater believ-ability, a more favorable evaluation ofthe product and advertisement, and asignificantly more positive purchase in-tention than advertisements using an"expert" or "typical consumer" endor-ser. Such effects were absent when ce-lehrity advertising was used inconjunction with a product high in fi-nancial, performance and/or physicalrisk (i.e., a vacuum cleaner). In generalhowever, celebrity endorsers werefound to be attractive and likeable.

Similarly, Freiden (1984) found thata celebrity advertisement for a televi-sion set (a product high in financial andperformance risk) generated highermean values for the likeabilit;y of thespokesperson as compared to ads fea-turing an expert, typical consumer orCEO. Measures related to the knowl-edge and believability of the spokes-person, product quality, trustworth-iness of the advertiser and purchase in-tent, did not reveal especially favorableratings.

Two additional studies, focusing onproducts high in social risk, supportfindings which suggest the effectivenessof using a celebrity endorser. Fried-man, Termini and Washington (1977)found that a celebrity endorsement fora fictitious brand of sangria scored sig-nificantly higher on a product-basedcharacteristic (probable taste); andmarginally higher on purchase intentthan did advertisements with no spo-kesperson. Believability, although

higher for the celebrity spokespersoncondition, approached but did notreach significance. Atkin and Block(1983) found that advertisements for abrand of alcohol which utilized celeb-rity endorsements produced consis-tently more favorable affective ratingsfor the advertisement and the productthan did advertisements using non-ce-lebrity endorsers. No difference in ad-vertisement believahility between ex-perimental conditions was evident.Similarly, behavioral purchase inten-tion, although higher for the celebrityversion of the message, uias not ob-served to be significant.

The use of celebrityspokespeople hasbeen on the rise.

In sum, these studies seem to suggestthat product type has a mediating effecton the overall effectiveness of using acelebrity as a product spokesperson.That is, products high in psychologicaland/or social risk seem to be hest suit-ed for such a strategy (cf., Friedmanand Friedman 1979). Even for theseproducts, however, purchase intentionis not consistently enhanced by such astrategy. Also, all studies report a directcorrelation between believability andoverall advertisement effectiveness asmeasured hy purchase intention. Thatis, in all studies discussed, an effect forbelievability was mirrored in the pur-chase intention measure. Togetherthese findings suggest that helievahilityhas not always been observed to be en-hanced through the use of a celebrityappeal.

This study examines a strategy de-signed to enhance the credibility of acelebrity spokesperson through the useof a two-sided appeal. Before discussingthat strategy, however, it is importantto understand the theoretical frame-work advanced to explain the effec-tiveness of advertising using celebrity

endorsers. This framework is intro-duced in the following section.

How Celebrity Ads Influence theConsumer. The effectiveness of celeb-rity advertising has been linked by someauthors, to the process of social influ-ence (cf., Friedman and Friedman1979). In a seminal work, Deutsch andGerard (1955) distinguished two formsof social influence. The first, termed"informational social infiuence," refersto "influence to accept information ob-tained from another as evidence attoutreality." The second, "normative socialinfiuence," refers to the influence toconform to another person or group.

Kelman (1961) was the first to iden-tify the processes of social influence.He suggested that there are three suchprocesses which, when pursued, facil-itate the potential that an individualwill accept Influence from another per-son or group: compliance, identificationand internalijiaiion. Identification andinternalization are particularly appli-cable to the study of celebrity endorse-ments.

Identification is said to occur whenan individual adopts the behavior ofanother person (or group). Because theindividual aspires to be like that personor group, adoption of the behavior en-hances the individual's self-image. Thisprocess relates to Deutsch and Ger-ard's normative influence type and hasbeen hypothesized to be strongly re-lated to affective characteristics of thecelebrity endorser such as likeahilityand attractiveness (Friedman andFriedman 1979). It is through the iden-tification process that celebrity en-dorsements achieve their effectiveness,particularly in the case of products highin psychological or social risk.

Internalization as a process of socialinfiuence relates to Deutsch and Ger-ard's informational infiuence type. It issaid to occur when individuals con-form to the attitudes or behavior ofothers because these actions or beliefsare perceived to be credible and arecongruent with one's own value sys-tem. It is the content of the inducedbehavior which is said to be rewardingto the individual. According to Kelman

(1961), the characteristics of the influ-encing agent play an important role ininternalization, but the critical dimen-sion is credibility.

The effectiveness of celebrity en-dorsements traditionally has not beenstrongly linked to this process, as a ce-lebrity's reason for promoting a prod-uct can just as easily be attributed bythe consumer to an external motive (i.e.,a monetary payment), as to an internalmotive (i.e., the celebrity's true beliefin the worth of the product). Hence,for this reason, the consumer's percep-tion of credibility of the advertiser suf-fers. This is especially true when theimage or knowledge base of the celeb-rity is inconsistent with that which theproduct requires. This may also explainwhy experts have been shown to per-form better than celebrities for ad- andproduct-based measures in the case ofproducts with higb financial, perform-ance or physical risks (Friedman andFriedman 1979).

An important issue relates to the de-velopment of a strategy for use in ad-vertising using celebrity spokespeoplewhich benefits from the dual supportof the identification and intemalizationprocesses of social influence. Indeed,prior empirical research has shown thatidentification and internalization canoccur concurrently as mediators of at-titude change (Mills and Harvey 1972;Romer 1979) and numerous studies inboth psychology and marketing havefocused on these processes (Burnkrantand Cousineau 1975; Cohen andGolden 1972; Norman 1976). It hasbeen established that the effectivenessof advertisements using celebrity en-dorsers is strongly linked to the iden-tification process of social influencethrough the dimension of likeability ofthe personality It remains to developa strong link to internalization by con-currently enhancing the credibility ofthe appeal. A two-sided approach tocelebrity endorsements may supply theanswer. Two-sided messages present theadvantages as well as slight disadvan-tages in the product's characteristics.This technique should increase believ-ability and therefore purchase inten-tion, as opposed to the traditional one-

sided appeal in which only positivecharacteristics are presented. This mayeven be the case for those products notonly typically best suited for promo-tion through a celebrity appeal.

Two-Sided Messages. As applied toadvertising, a two-sided message in-volves those instances when a com-municator claims that the advertisedproduct performs well on attributeswhich are important determinants ofproduct usage. Product performanceon less-important characteristics mightbe disclaimed and/or limited in scope.Alternatively as noted, a one-sidedmessage only presents positive aspectsof the product. In the use of two-sidedappeals, if an attempt is made to dilutethe significance of negative claims madewithin the text of the communicationon an attribute-specific basis, then thead is termed two-sided refutational. Ifno such attempt is made, then the adis said to be two-sided non-refutationalin nature.

. . . Studies suggestthat product type hasa mediating effect onoverall effectiveness ofa celebrityspokesperson.

Relevant research has shown thetwo-sided non-refiJtational message tobe higher in credibility than the two-sided refutational communication (Ka-mins 1984; Kamins and Assael 1987).In relation to our intent to increase thecredibility of celebrity advertising, theseresults suggested that the two-sidednon-refutational message would be themore appropriate technique to apply.

Research on two-sided non-refuta-tional appeals has typically comparedthis executiion witb that of the one-sided approach. This research hasshown that two-sided non-refutational

appeals were more effective than one-sided communications in increasingcopy believability (Etgar and Goodwin1982; Golden and Alpert 1978, 1987;Kamins 1985; Settle and Golden 1974;Smith and Hunt 1978; Swinyard 1981).Attempts to influence product ratings,intentions or attitudes through the useof such appeals have met with only lim-ited success, despite the appeal's ap-parent positive effect upon credibility.In celebrity endorsements, however, atwo-sided approach may effectively in-fluence purchase intention since the useof celebrities has already been shownto positively impact upon a subject'saffective reactions to the advertise-ment. Added credibililty gained by two-sidedness may be enough to dramati-cally increase purchase intention as wellas the subject's impression of the ef-fectiveness of the ad and the image ofthe sponsor.

Hypotheses

H5: The ratings of ad credibility andeffectiveness will be significantlyhigher for celebrity endorse-ments using a two-sided as op-posed to a one-sided format.

H;: A celebrity endorsement pre-sented in a two-sided form willlead to a significantly highersponsor evaluation ratings onoverall quality of service than aone-sided endorsement.

H3: Purchase intention for a two-sided celebrity endorsement willbe significantly higher than thatobserved for a one-sided en-dorsement.

Methodology

Product. A service (a managementconsulting firm) was used in this studyA consulting service can be classifiedas high in both financial and perform-ance risk, and therefore may not be theoptimal choice for use of a celebrityappeal (cf., Friedman and Friedman1979). Therefore, by design, the choiceof this service should make the obser-vation of a significant "sideness" effect

difficult, and if evident, such an effectshould be more robust than had aproduct high in social and/or psycho-logical risk been studied. A consultingservice was selected because a majorityof small- to medium-sized businessesfece situations which compel them toconsider outside sources of support toarrive at feasible and effective solutionsto business problems. The advantageof advertising a management consult-ing service was the ability to appeal toa number of different business types,thereby diminishing the possibility thatfindings are anchored to a specific in-dustry. The company used (HighlandDecision Systems) was new and, there-fore, had a small share in the marketarea investigated. At the time of thestudy, they had not yet advertised theirservices.

Sample. The subjects were owners orCEOs of small- to medium-sized busi-nesses with under $10 million in an-nual gross sales and less than 200employees. A proportional quota sam-ple of 52 businesses in the greater LosAngeles region was completed basedon the actual distribution of the in-dustries within that region. The sam-ple was selected using StandardIndustrial Classification (SIC) codes andlistings of local merchants who metboth the industry and size require-ments. The industries selected includ-ed manufacturing, high-tech products,consumer products, health care, retail,transportation, marketing and busi-ness service companies. This cross sec-tion was designed to be general enoughto cover the range of small- to medium-sized business arenas, while allowingthe experimenters an opportunity toscreen industries and those specificcompanies that were not likely to con-sider management consulting services.

In addition to meeting the require-ment of being the owner or CEO ofthe company, executives included in thesample had to have the decision-mak-ing power to evaluate and adopt theadvertised service. Identification of thekey individual for each company wasacquired through pre-telephone con-tact with his/her office and/or public

information. Time constraints on manyof the executives contacted precludedtheir completion of the interview. Thefindings discussed here are based upon52 completed interviews.

. . . research hasshown the two-sidednon-refutationalmessage to be higherin credibility than thetwO'sided refutationalcommunication . . .

Advertisements. Two full-page, black-and-white advertisements were createdto reflect the two experimental con-ditions; that is, an advertisement usinga celebrity spokesperson making prod-uct-related statements in either a one-sided or two-sided non-refutationalform. The celebrity endorser chosenwas Leonard Nimoy. Nimoy was se-lected on the basis of pretests in which12 male celebrities were rated on fivepersonal characteristics of a spokes-person. These characteristics, drawnfrom prior research, were: (1) credibil-ity; (2) trustworthiness; (3) believabili-ty; (4) identifiability and (5) consistencyor congruence of the spokesperson'simage with the product. The test wasadministered at a major West Coastuniversity using 20 undergraduatebusiness students as subjects. The 12male celebrities had previously beenidentified as satisfying a high likeabilityrequirement (i.e., Leonard Nimoy, TomSelleck, William Shatner, and MelGibson, among others). Celebritieswere rated using seven-point scales (e.g..1 = not at all credible; 7 = completelycredible). Four celebrities were ob-served to be above the scale midpointon measures of credibility, trustwor-thiness and believability. In addition,their images were found to be con-gruent with the image of a spokesper-

son for a management consultingservice (see Kahle and Homer (1985)for a discussion of congruence as it re-lates to celebrity appeals). Additionally,all 20 subjects were able to correctlyidentify a television show or movie inwhich these four celebrities appeared,lending face validity to the claim ofidentifiability for each.

A second test, involving a sample of10 business owners or CEOs of small-to medium-sized companies in the tar-get area of the study was undertaken.These individuals were asked to ratethe four remaining celebrities on thesame scales used in the earlier test.Leonard Nimoy was the only celebritywho scored above the scale midpointon each measure and was correctlyidentified by each subject.

Advertisements were identical inlayout and spacing. Clad in a businesssuit, Nimoy appeared on the left sideof the ad. Copy appeared on the rightside as a personal statement from thecelebrity. The ad copy for the one-sid-ed communication appeared as follows:

"You've launched your businessand you're headed at full speedtowards the 21st century. Youknow your product is good, andyou have the expertise to provideyour company with the productinnovations to keep you an in-dustry leader. But you've begun tonotice that your business is push-ing hard to keep up the pace.

This is where the ManagementExperts at Highland Decision Sys-tems can help. I know. . . I usethem in my business.

Highland Decision System... TheSmall Business Experts. The log-ical choice to take your businesswhere no business has gone be-fore."

The two-sided advertisement wasidentical to that of the one-sided withthe addition of the following disclaimerat the end of the second paragraph:

"They aren't the best known busi-ness consultants,... Just the best."

The attribute used in the disclaimerwas selected on the basis of two criteriain pretest: (1) a moderate degree of im-portance, and (2} consistency in eval-uation. Prior research in the messagesidedness area has shown that disclaim-ing too important an attribute maynegatively impact purchase intention(Settle and Golden 1974; Smith andHunt 1978); whereas disclaiming toounimportant an attribute may have lit-tle, if any, effect upon credibility of theadvertiser. Pretests revealed that the at-tribute relating to prior knowledge ofthe company best fit the above criteriafor disclamation.

Experimental Procedure. An ap-pointment was made well in advance,and the instrument was administeredto each executive at his/her place ofbusiness. The experimental guise in-volved asking subjects to serve as "ex-pert judges" in the evaluation of aproposed advertisement for a univer-sity-sponsored advertising competi-tion. Such a guise was designed to avoida demand effect where the executivewould feel committed to a favorableevaluation of the advertisement. Fifty-two subjects participated in the study

Subjects were initially exposed to oneof the advertisements for a period oftwo minutes. They were asked to takethis time to read the ad carefully, withthe understanding that a short ques-tionnaire, focusing mainly on the ad,was to follow. Subjects then completedthe questionnaire by responding toquestions related to the effectivenessand credibility of the ad; the evaluationof the company on a measure of overallquality of service; and purchase inten-tion (i.e., fijture use of the service). Thequestionnaire ended with classificationquestions related to the subject's busi-ness characteristics such as businesstype, number of employees, approxi-mate yearly sales and current and pastuse or non-use of consulting services.By design, the number of questions waskept to a minimum given the nature ofthe sample (executives) and their con-cern for effective time management.After completion of the questionnaire,subjects were thanked for their partic-

ipation and debriefed.The dependent variables measured

were:

Advertisement Evaluation. The subject'soverall evaluation of the advertisementon credibility and effectiveness wasmeasured respectively on 7-point scalesranging from not credible (1) to credible(7); and ineffective (1) to effective (7).

Sponsor Evaluation. Subjects wereasked to evaluate the sponsor (High-land Decision Systems} on overall qual-ity of service. This measure was codedon a 7-point scale ranging from poor(1) to excellent (7).

Purchase Intention. This measure re-quired respondents to indicate their in-clination to use Highland DecisionSystem's services based upon a readingof the given advertisement. The scalewas anchored by not inclined (1) andstrongly inclined (7).

. . . disclaiming tooimportant an attributemay negatively impactpurchase intention . . .

Independent Variable: As noted ear-lier, the study manipulated the sided-ness of the celebrity spokesperson'scomments regarding the sponsoringcompany, creating two experimentalgroups. Twenty-six subjects respondedto the one-sided celebrity appeal, whilean equal number responded to the two-sided celebrity appeal. The data wereinitially analyzed in a multivariate fash-ion through the use of Hotelling's T^procedure for all dependent measuresconcurrently. Conditional upon ob-served significance, ensuing data anal-ysis proceeded through the use of pair-wise t-tests for each of the dependentmeasures separately.

To ensure that the two experimentalgroups did not significantly vary oncompany-specific characteristics, meas-ures relating to annual sales, number

of employees, type of business classifica-tion and the proportion of companieswho currently use consulting serviceswere examined. Results showed no sig-nificant effects for each measure con-sidered in terms of annual sales( t=1.46) , number of employees(t=1.40); type of business classifica-tion (chi-square = 4.02), and propor-tion who currently used consultingservices (t = .87)- These findings sup-ply evidence that the two experimentalgroups did not initially differ on im-portant measures relating to company-specific characteristics, and discountsthe use of such measures as confound-ing variables in explaining experimen-tal effects.

Results

An overall multivariate Hotelling T^procedure was utilized to determine ifa significant difference was evident be-tween the experimental conditionswhen all four dependent measures wereconsidered simultaneously. Resultsshowed that this was the case(T^ = 7.29, p<.001) and conditionalupon this observed significance, a testof each hypothesis was undertaken withthe use of univariate t-tests.

Hypothesis 1: The findings presentedin Table 1 for advertisement evalua-tions lends strong statistical support tothe first hypothesis. That is, subjects'evaluation of advertisement credibilitywas higher for those exposed to thetwo-sided celebrity appeal (x = 4.85)relative to those exposed to the re-spective one-sided communication(x = 4.31). A pairwise one-tailed Stu-dent's t-test revealed this difference tobe statistically significant (t = 3.27,p:<.005). Moreover, those exposed tothe two-sided communication rated itsignificantly more effective (x = 4.85)than the one-sided advertisement(x = 4.38, t = 2.79, p< 005).

Hypothesis 2: The next step was todetermine if the positive impact of sid-edness upon advertisement credibilityand effectiveness also was refiected inan enhancement of the image of thesponsor in terms of overall quality of

8

service. The findings presented in Ta-ble 1 indicate that this was indeed thecase, lending statistical support to Hy-pothesis 2. Subjects exposed to the two-sided communication evaluated thesponsor as significantly higher in over-all quality of service (x = 5.00) thanthose exposed to the alternative one-sided appeal (x = 4.61, t = 2.28, p<.01).

Hypothesis 3; This hypothesis fo-cused on the subject's intention to usethe sponsor's services based upon ex-posure to the advertisement. The find-ings as presented in Tahle 1 supportthis hypothesis, with subjects exposedto the two-sided communication indi-cating greater intention (x = 4.31) thanthose exposed to the one-sided ad(x = 3.69. t = 2.01, p< 025).

Discussion

The results of this study are encour-aging in that they indicate the effec-tiveness in use of a two-sided as opposedto one-sided celebrity spokespersonappeal across three distinct levels. First,ad-related variables such as credibilityand effectiveness were significantly en-hanced. Significant results for credi-bility is rare in research of this type,and the findings evident here are con-sistent with the interpretation that sid-edness enhances credibility through theidentification process of social influ-ence. Moreover, the sponsor receivedsignificantly higher ratings on overallquality of service and subjects' revealeda significantly greater intention to usethe company to tackle consulting prob-lems.

Although the results of the currentresearch are impressive, conclusions asto their relative meaning await a com-parison with mean values derived fromnon-celebrity advertisements varyingin sidedness and product type. This wasnot the goal of the current study. Theresearch focus here was simply to com-pare a strategy of two-sidedness in ce-lebrity endorsements with the moretraditional one-sided approach.

The current study does suggest thatsidedness in celebrity endorsementsholds great potential for advertisers.Future research should investigate this

issue in greater depth through consid-eration of other variables such as prod-uct type (i.e., a service vs. a productand/or high vs. low involvement prod-uct classes); status of endorser (i.e., ex-pert, company president, typicalconsumer and celebrity); and the var-iation in importance and number of at-tributes disclaimed.

Finally, advertisers today seem to bekeenly attuned to the attributionalprocesses through which subjects infera spokesperson's reason and rationalefor advertising a product (Folkes 1988;Kamins and Assael 1987). The recentuse of celebrities in advertising whomake the claim that they have neverserved as a spokesperson before (i.e.,George C. Scott for Renault) is a directattempt by advertisers to influenceconsumers' attributional processes.That is, it is hoped that consumers wiltattribute the celebrity's involvement inthe product to his/her firm belief inproduct quality and service (or othersimilar attributes) rather than just themonetary reward. Hence, this strategyas outlined above and the use of a two-sided communication both have a goalof increasing advertiser credibility. Infuture research, it would be useful tostudy the interaction between these twostrategies as well as the attributionalprocesses which underlie their effec-tiveness.

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TABLE 1Mean, Standard Deviation and t-Test Results for One-Sided

and Two-Sided Advertisements Utilizing a Celebrity Spokesperson

Experimental ConditionOne-Sided Ad

(n = 26)Two-Sided Ad

(n = 26)t-TestResult Sig-

Dependent MeasureAdvertisement Evaluation

Credibility

Effectiveness

Sponsor EvaluationQuality of Service

Purchase Intention

X = 4.31s = .63x = 4,38s = .65

x-4.61s= .51X = 3.69

X = 4.85s= .56X = 4.85s = .56

x = 5.00s = .71x = 4.31

3.27

2.79

2.28

2.01

.005

.005

. 01

.025

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Received August 31, 1987. Rei;ision acceptedfor publication December 13, 1988.

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