Celebrity Testimonials | cpi CELEBRITY PERFORMANCE

Testimonials: Do They Increase the Effectiveness of Advertising Campaigns?

Excerpt from the study, published October 18, 2013.

Increasing brand awareness and affinity, and, ultimately, increasing the target audience’s desire to make a purchase are all objectives pursued by marketers when they use celebrity testimonials in their campaigns.

cpi CELEBRITY PERFORMANCE and respondi AG conducted an empirical study to investigate the extent to which brands such as L’Oréal, Head & Shoulders and Sparkasse have had success with their current testimonial campaigns.

The idea of using celebrities as potent brand ambassadors in marketing is almost as old as marketing itself. The use of testimonials in advertising has seen a dramatic increase around the world, especially in the past 20 years. Marketers hope that testimonials will, in particular, increase brand awareness and affinity, give the brand a positive boost with the testimonial’s image, and ultimately increase the target group’s desire to make a purchase.

The present empirical study analyzes the extent to which brands such as H&M, L’Oréal, Edeka, Philips and Sparkasse have been successful in these terms with their current TV commercials featuring celebrity testimonials such as Beyoncé Knowles, Heike Makatsch, Kaya Yanar, Sylvie van der Vaart and Martina Hill.

Celebrity Testimonials: the Opportunities

Kaya Yanar shops at Edeka, Sylvie van der Vaart brushes her teeth with Philips, and Beyoncé Knowles wears H&M. Using celebrities in marketing campaigns is the trend. Stars are enjoying steadily increasing popularity as brand ambassadors. One out of every eight ads in Germany features a celebrity testimonial. It’s no wonder, because in these times of market saturation and an almost bewildering array of functionally similar products with marginal differences in quality, a strong brand is what guarantees market success. To successfully stand out from the competition and add an emotional boost to the brand, companies often call upon prominent personalities as testimonials.

The current study by cpi CELEBRITY PERFORMANCE and respondi tested the TV campaigns with celebrity testimonials listed in Table 1.

Table 1: Calculated cpi-Spot-Performance-Index for the 16 TV commercials tested

From a business perspective, there can be a variety of reasons for opting to use a celebrity testimonial. According to a study conducted by cpi CELEBRITY PERFORMANCE in conjunction with the Celebrity Marketing Alliance,^[2] marketing decision makers are pursuing the following goals when they decide for a celebrity testimonial:

a substantial increase in brand affinity;
a higher increase in brand awareness than would be expected from non-testimonial campaigns;
positive impact on brand image through the celebrity’s personality;
sharpening the brand’s image profile in a specific way;
increasing the target group’s desire to make a purchase.

From the massive amount of information that bombards consumers in the various communication channels we use nowadays, only a fraction is consciously perceived. A well-known face in an ad is often an effective way to catch the attention of consumers and increase the perception of the advertising message. Celebrity testimonials thus help advertising communication penetrate consumers’ selective perceptual filters into their consciousness. The increased perception and recall triggered by testimonials is often reflected in higher brand awareness. A high brand affinity and a strong brand image are other important drivers of brand performance and can often justify a significant price premium over competing brands. By linking a brand with a prominent spokesperson, both the affinity and image of the advertised brand can be substantially increased. Companies seek to have consumers transfer their positive image of the celebrity onto the brand and add emotional charge to the brand in terms of relevant personality traits (what is known as image transfer). Ultimately, marketers hope that the positive effects of endorsements on brand awareness, likeability and image also result in an increase in sales.

Celebrity Testimonials: the Risks

Used correctly, celebrities can bring a range of positive effects on the success of a brand and a company. But be careful: not every partnership between celebrities and brands is successful. Using a celebrity as a spokesperson involves certain risks. Celebrities are usually integrated into campaigns designed to reach wide masses. In particular, TV endorsements are usually associated with high costs, including the celebrity’s fees, production costs, and the purchase of air time. If such a campaign does not produce the intended positive effects on aspects such as brand awareness or brand image, the marketing department has squandered its scarce human and financial resources. In the worst case, a prominent brand ambassador can cause a brand short, medium and even long term harm, e.g. if he or she is linked more to scandals than to positive headlines and transfers negative image aspects to the brand. The image losses suffered can sometimes be several times higher than the just the costs of a wasted campaign.

Current Testimonial Campaigns: Objectives of the Study

This study investigates the impact that current TV spots featuring celebrities have on the attitudes and behavior of consumers. Specifically, the following questions are addressed for sixteen current TV campaigns featuring celebrity testimonials:

How well are the brands’ commercials recalled against the competitive environment? How do consumers judge these spots in detail?
Which spots and brands benefit from the celebrities in terms of the spot’s impact?
What is the impact of celebrities on the marketing KPIs of brand likeability and intention to purchase the brands and products advertised?
To what extent is the image of the brands advertised changed by the celebrity? What facets of the brand image are strengthened or weakened by the celebrity?
Which brands gain from using a celebrity spokesperson?
To what extent can marketers predict in advance whether a celebrity testimonial will have a positive or negative effect on the spot’s impact, the brand affinity, the brand image and the intent to purchase?

For in-depth answers to these questions, we conducted a comprehensive survey of the key demographic of 14-49 year olds. First, the effects of eight television commercials’ advertising products with a primarily female target audience (such as Veet, taft) were studied. Then, eight TV spots for brands and products which should be relevant to both women and men (such as Sparkasse, VHV) were studied. To reflect this set-up, only women were interviewed concerning the first eight spots, while an equal survey (50% each) of men and women was conducted for the second group. In the period from August 9-19, 2013, a total of 2,084 interviews were conducted. At least 250 people were asked about each TV spot and at least 200 people were asked about each celebrity.

In the first part of the survey, the two groups of respondents were played an advertising block of eight TV spots. The order of the spots was varied randomly among the respondents. Immediately after the advertising block, an open question was asked about the respondents’ recall of the ads. Then two spots from the advertising block were replayed for each respondent, followed by questions about his or her assessment of the ads, the likelihood that he or she would purchase the advertised product, brand affinity and brand personality. The respondents were then also asked whether they recognized a celebrity in the spot and, if so, whom.

In the second part of the survey, respondents were shown the photos and names of the eight celebrities who had appeared in the advertising block they had watched earlier. First, respondents were asked whether and to what extent they knew each of the celebrities. Then, each respondent was given two randomly selected celebrities whom he or she had indicated they knew by photo and name. The respondents were then asked for their assessment of the celebrities’ image and personality as well as their ability to act as testimonials for certain product categories.

Impact of Testimonials: Measuring the Effect on Spot Performance, Brand Affinity, Purchase Intent and Brand Personality

Differences in the performance of TV spots can, of course, be due to all sorts of aspects, for example, different concepts, story or editing. A significant driver of the spot performance could also be the featured testimonials – at least that is what advertisers believe. Whether this is the case and how celebrities can influence key marketing performance measures such as brand affinity, purchase intent and brand personality is analyzed in the following part of the study.

As stated in the introduction, marketing decision makers expect celebrity testimonials to have a positive influence on consumers’ attitude towards the brand (in terms of increased brand affinity and a sharpened brand image) and behavior (in the form of increased intent to purchase) that goes beyond a simple improvement of the spot’s performance.

In order to isolate the influence of the celebrities in the sixteen TV commercials with testimonials tested, we compared how both a test group and a control group assessed the celebrity-brand relationship for each commercial: the test group included those respondents who noticed the celebrities in the spot. The control group consisted of all those who did not notice any celebrities in the spot. Since the two groups are differentiated on the basis of recognizing the celebrity or not, the differences in their assessment of the spot, brand affinity, intent to purchase and brand image can be traced to the impact of the celebrity testimonial.

Impact of the Testimonial on Spot Performance

First, we answer the questions whether and to what extent celebrity testimonials are capable of increasing a spot’s impact. Across all respondents and brands, celebrities had, on average, a consistently positive influence on the aspects of the spot we were investigating (see Fig. 1).

Fig. 1: Assessment of the eight spot impact dimensions.

Basis: all respondents (2,084); calculated as averages of the top 2 boxes on a scale from 1 = “strongly disagree” to 7 “strongly agree” (question: “To what extent do the following statements apply to the TV commercial for … ?”)

To determine the extent to which each spot benefited from its celebrity testimonial, we calculated the Spot Impact Improvement Factor. This indicates the factor by which the spot impact was increased by the celebrity testimonials (see Fig. 2).

Fig. 2: Spot Improvement Factor for the 16 TV spots tested

*Significant differences in the assessment of the spot (across all dimensions) between the test and control group (p < 0.1, using variance analysis).

A glance at Fig. 2 shows that almost all advertised brands were able to benefit from their celebrity testimonial. The additional variance analyses indicate that there were statistically significant positive differences in the assessment of the spot between those persons who recognized the celebrity in the ad and those who did not for the nine top-ranked spots.

The TV commercials for Head & Shoulders 2-in-1 and Lascana showed the strongest impact: both Mats Hummels and Sara Nuru ensured that the spots were much better assessed on all collected assessment dimensions. Respondents who recognized Mats Hummels and Sara Nuru in the spots gave the spot better rankings, on average, by a factor of 1.2 over people who did not. In addition, the spots for taft Ultra, the Sparkasse current account, Edeka, Veet Easy Wax, Philips Sonicare Diamond Clean, belVita Frühstückskeks and the Dacia Lodgy also benefited significantly from their celebrity testimonials.

Impact of Testimonials on Marketing KPIs: Purchase Intent and Brand Affinity

However, a good spot performance is only a means to an end. Companies ultimately use testimonial campaigns to achieve significant increases in purchase preference and, as an important long-term driver of market success, in brand affinity. While a purchase preference can often change over a relatively short term, depending on the product group, brand affinity is a construct that usually only changes in the medium to longer term. The latter is particularly true for well-known brands, as their brand affinity and brand image have been built and strengthened over a long period.

Our test showed that the probability of purchase for belVita Frühstückskeks, Head & Shoulders 2-in-1, Lascana and Veet Easy Wax could be significantly increased by the respective celebrity testimonial (see Table 2):

Table 2: List of products where the probability of purchase was significantly increased by the celebrities (p ≤ 0.1) (variance analysis)

* Shown are the mean values of the top 2 boxes on the question of the purchase probability on a scale from 1 = “very unlikely” to 7 = “very likely”.

While only 13.4% of those persons who did not recognize Annette Frier in the belVita spot indicated that they would likely buy belVita Frühstückskekse the next time they purchased cookies, 22.3% of those who did recognize Frier indicated that they would. Sara Nuru has a similarly strong effect on consumers’ purchasing preference: 21.4% of those who recognized her indicated that they would buy the product, while only 12.8% of those who did not recognize her were swayed towards a purchase. Jorge Gonzalez (from 27.3% to 35.4%) and Mats Hummels (from 17.0% to 24.7%) successfully contribute to an increase in the probability of purchase for Veet Easy Wax and Head & Shoulders 2-in-1, respectively.

A similar study of brand affinity shows that, in seven of the sixteen spots, the testimonial contributed to a significant increase in brand affinity (see Table 3):

Table 3: List of brands, whose brand sympathy is significantly increased through the celebrity (p<0,1, (variance analysis)).

* Displayed are the average values of the top 2 Boxes to the question, how likeable the brand is on a scale from 1=“not at all likeable” to 7=“very likeable“.

Annette Frier, Sara Nuru, Mats Hummels and Jorge Gonzalez helped the products they were advertising to not only a higher probability of purchase, but also higher affinity to the associated brands. Similar results were shown for H&M with Beyoncé, Philips Sonicare with Sylvie van der Vaart, and taft with Heidi Klum. Given the fact that H&M, Head & Shoulders, and taft are already long-established brands and products on the German market, the resulting strong impact of the endorsement is all the more remarkable.

Impact of Testimonials on Brand Personality

Marketers often cite the positive transfer of a celebrity’s personality to the brand being advertised as an important argument for using a testimonial. Evidence for this includes the significant (p < 0.05) positive correlations between various personality facets of the celebrities and the brands tested in our study. Across all respondents and brands studied, that of fourteen personality traits assessed for the celebrities, elegance, attractiveness, charisma, trendiness, competence, extravagance and honesty were the ones most particularly transferred to the brand advertised. However, looking at the aspects of image transfer at the level of individual brands also shows that the use of testimonials triggers different degrees of leverage in terms of brand personality and its facets, depending on the brand (see Table 4).

Table 4: Brand image attributes with significant increases in attribution related to the celebrity (p ≤ 0,1) (variance analysis).

The brands H&M, Head & Shoulders, Lascana, Philips Sonicare and Veet benefited in many ways from a positive image transfer from their testimonial to the brand. All fourteen brand personality dimensions studied were attributed significantly stronger to Lascana when associated with Sara Nuru. As Fig. 3 shows, the effect is strongest for trustworthiness (+19%), attractiveness (+17%), elegance (+14%) and brand competence (+13%).

Fig. 3: Perception of Lascana’s brand personality

Displayed are the mean values of the top 2 boxes concerning attribution of certain aspects to the brand on a scale from 1 = “strongly disagree” to 7 = “strongly agree”.

Another example for wide-ranging image transfer effects is H&M: Beyoncé came across as particularly fresh, elegant, attractive, charismatic, trendy, hot blooded and cool, and consumers associated these image attributes with H&M to a much greater extent when the brand was associated with Beyoncé (see Fig. 4).

Fig. 4: Perception of the brand personality of H&M.

Displayed are the mean values of the top 2 boxes regarding the question of the attribution of the relevant aspects related to the brand on a scale from 1 = “strongly disagree” to 7 = “strongly agree to”.

We can only make conjectures about the target image for the individual brands because such information was not provided by the advertisers. Therefore, one must certainly keep in mind that companies may wish to strengthen or reposition their brands with a celebrity testimonial only with respect to individual aspects of their brand image. Assuming L’Oréal wanted to position L’Oréal Excellence Creme as a reliable brand with Heike Makatsch as its celebrity spokesperson, this goal was achieved: people that associated Heike Makatsch with the brand gave the brand significantly higher scores in reliability (+7%). The same applies, for example, to Olaz in terms of the image attributes elegance (+9%) and competence (+4%), or for Edeka concerning aspects of freshness (+12%) and trendiness (+5%).

For belVita, Dacia, Sparkasse and Sheba, no significant image transfer from the celebrity endorser to the brand could be detected in this study. As already mentioned, this could, for example, be attributable to the fact that a brand image transfer only occurs in the medium- to longer-term and therefore could (still) not be determined in this study.

Smart Marketing with Celebrity Testimonials: Tools for Selecting Testimonials and Ensuring Successful Testimonial Campaigns

”Afterwards one is always wiser”, but marketers face the challenge of having to make the right decisions regarding the use of celebrity testimonials before the campaign is launched. That’s why they have to ask: how can a potential testimonial influence the perception (brand affinity, brand image, etc.) and preferences (purchase likelihood, etc.) of my target audience? Three dimensions, the cpi-Index, the cpi-Celebrity-Brand-Fit-Index and the cpi-Product-Categories-Fit, help marketers answer this question and find the ideal testimonial. The usefulness of these three dimensions was demonstrated empirically for the sixteen commercials tested.

Three Conditions for Effective Testimonials

The basic prerequisite for a celebrity testimonial to have a positive effect on a brand is celebrity’s ability to exert a positive influence on the target group’s attitudes and behavior. For this, the celebrity needs a sufficient reach within the target group (i.e. awareness) as well as a strong image (such as popularity, opinion leadership, trustworthiness, etc.) in order to exert an influence on those familiar with him or her. In order for this potential to be fully exploited and the intended image transfer from the celebrity to the brand to take place, there needs to be adequate fit between the perceived personality of the celebrity and the (target) brand image. Only then will the celebrity help strengthen or reposition the brand as desired. In addition, the celebrity must also be a credible ambassador for the product to be advertised. If these three rules are followed, the likelihood of a successful endorsement campaign is very high.

Choosing the Right Testimonial: Three Indicators as Relevant Basis for Decisions

cpi CELEBRITY PERFORMANCE has developed three key indices and fit indicators that address the three rules for successful testimonial marketing and form the basis for right decisions.

cpi-Index: Leading scientific method for the empirical prediction of a celebrity’s ability to have a positive influence on a specific audience’s attitudes and behavior.

cpi-Celebrity-Brand-Fit-Index: Empirical method for determining the degree of coherence between the celebrity’s personality and the brand’s target personality.

cpi-Product-Categories-Fit: Empirically determined indicator that measures the ability of a person to act as an effective endorser for a specific product category.

cpi Indices Successfully Predict the Effectiveness of Testimonials

In this empirical study, the cpi-Index for sixteen celebrity testimonials was calculated. The index measures the construct of image strength and awareness. Image strength, measured with six key image facets, quantifies the potential influence of a celebrity on consumers. Associated with the celebrity’s reach within the target group (i.e. his or her level of familiarity), the cpi-Index provides an indicator of the potential advertising impact on the whole target group.

In the present study, there are significant positive correlations (p < 0.05) between the construct of image strength across all celebrities, spots and brands and:

general favorability of the spot;
six of the eight dimensions for assessing the impact of the spot;
brand affinity; and
the likelihood of a purchase.

This result shows that the image strength, a central component of the cpi-Index, is a useful measure for predicting the influence of celebrities on spot performance, brand affinity and the likelihood of a future purchase.

A good match of the celebrity to the advertised product category is also an important factor influencing the effectiveness of endorsement campaigns. Our analysis indicates significant positive correlations between the cpi-Product-Categories-Fit determined for each of the 16 celebrities and the spot assessment dimensions of ”makes me curious about the product,” “fits the product,” and “makes me want to use the product.” This means that a celebrity perceived as a suitable endorser for the product category being advertised significantly contributes to the spot making consumers curious about the product and inspires them to try it. The Product-Categories-Fit, however, is less relevant to the ease of understanding the ad or liking the spot: consumers may, of course, also perceive a spot as likeable or understandable even if they think the celebrity is not a suitable endorser for the product being advertised. For a spot to influence consumer behavior, a sufficient Product-Categories-Fit is, however, extremely important. This is reflected in the documented positive correlations between aspects of spot impact (“curious,” “fitting,” “inspiring”) and the cpi-Product-Categories-Fit.

The cpi-Celebrity-Brand-Fit-Index determines whether a celebrity is able to change the image of a brand in the desired manner cannot be determined in the present study. The in-house information about the target brand image was not available to us. We will be glad to investigate the cpi-Celebrity-Brand-Fit for your brand and alternative celebrities. It does serve as a reliable indicator of whether a celebrity endorsement has the potential to strengthen or change your brand image.

Summary of the Study and Implications for Testimonial Marketing

As this study shows, almost all sixteen advertised brands were able to benefit from their celebrity testimonial, either in terms of the perception of the campaign itself or even in terms of purchase intent and brand image. On average, the celebrities had a thoroughly positive impact on the assessment of the spots with regard to the marketing KPIs for the products advertised. In order to forecast whether a celebrity would be an effective endorser for a specific brand and campaign, three key metrics can be used.

Spot Performance

Across all sixteen testimonial campaigns tested, celebrities had a consistently positive influence on the aspects of spot performance we were investigating (spot impact).
For nine of the spots, there was a significant positive influence of the testimonial on the spot impact. The TV commercials for Head & Shoulders 2-in-1 and Lascana showed the strongest impact from their respective spokespersons, Mats Hummels and Sara Nuru.

Purchase Intent and Brand Affinity

Our test showed that the probability of purchase for belVita Frühstückskeks, Head & Shoulders 2-in-1, Lascana and Veet Easy Wax was significantly increased by the respective celebrity testimonial.
Annette Frier (belVita), Mats Hummels (Head & Shoulders), Beyoncé Knowles (H&M), Sara Nuru (Lascana), Sylvie van der Vaart (Philips Sonicare), Heidi Klum (taft) and Jorge Gonzalez (Veet) contributed to significantly higher affinities with the brands they advertised.

Brand Personality

The perception of an advertised brand was also shown to benefit from the positive image transfer from the testimonial’s personality: Across all respondents and brands studied, of fourteen celebrity personality traits assessed, elegance, attractiveness, charisma, trendiness, competence, extravagance and honesty were the ones most commonly transferred to the brand advertised.
For twelve of the sixteen brands studied, significant image transfer was identified. The brands H&M, Head & Shoulders, Lascana, Philips Sonicare and Veet benefited in many ways from a positive image transfer from their testimonial to the brand.

Smart Marketing with Celebrity Testimonials

In addition to the proven positive effects, it should be noted that the use of celebrity testimonials does involve risks which, in extreme cases, can even result in damage to the brand itself.
To help with this challenge, three empirically determined dimensions for identifying and selecting the best celebrity testimonial, the cpi-Index, the cpi-Celebrity-Brand-Fit-Index and the cpi-Product-Categories-Fit, all provide a demonstrably strong basis for successful testimonial campaigns.

Detailed Results

The detailed results for the testimonial campaigns, brands and celebrities studied will be provided upon request by email to .

[1] Cf. Absatzwirtschaft [08/19/2014, 2:00pm].

[2] Cf. “Celebrity Marketing in Deutschland,” a study of the Celebrity Marketing Alliance in cooperation with W&V, available here as a free download (in German).
October 18, 2025