The Effect of Consumer Testimonials and Disclosures 

on Ad Communication for a Dietary Supplement 

Report submitted to Federal Trade Commission

Manoj Hastak, Ph.D.

Michael B. Mazis, Ph.D.

September 30, 2003
The Effect of Consumer Testimonials and Disclosures 

on Ad Communication for a Dietary Supplement 

Background 

A consumer survey was conducted to examine the communication effects of a promotional 

booklet for a dietary supplement. The booklet consisted entirely of three pages of consumer 

testimonials, primarily from senior citizens, touting the product's efficacy for treating various 

diseases and conditions. 

Research Questions 

! Do testimonials communicate product efficacy?

! Do testimonials communicate typicality?

! Do disclosures qualify claims conveyed by testimonial ads?

! Does the disclosure language make a difference in qualifying claims conveyed by testimonial

ads? 

! Do consumers notice prominent disclosures in testimonial ads? 

Methodology 

The study used a mall-intercept design and was conducted in seven geographically diverse 

shopping malls. The study sample consisted of 200 dietary supplement users who reported 

suffering from breathing problems, low energy or chronic pain. The sample was half male and 

half female. Eighty percent of respondents were 60 years of age or older, which was the primary 

target audience for the dietary supplement. 

There were five "booklet" groups and one "no booklet" group: 

• Respondents in the "no booklet" group were shown a one-page letter touting the dietary 

supplement as an "astonishing" nutritional product. The letter did not contain any 

testimonials and did not mention any specific health conditions or diseases (group 1). 

• Respondents in the five "booklet" groups were shown the letter together with a three-page 

booklet consisting of 18 testimonials extolling the virtues of the dietary supplement for 

breathing problems (e.g., asthma), fatigue and low energy, and chronic pain (e.g., arthritis). 

One "booklet" group was shown the booklet without any disclosure (group 2). The other four 

"booklet" groups were shown the booklet with one of the following prominent, boxed 

disclosures in 14-point type at the bottom of each page of the booklet: 
Long disclosure: "DISCLAIMER: These testimonials do not imply that similar results 

will happen with your use of our products. These testimonials are not intended to 

recommend any supplement as a drug, as a diagnosis for specific diseases or conditions, 

nor as a product to eliminate diseases or other medical conditions or complications. We 

make no medical claims as to the benefits of any of our products to improve medical 

conditions." (hereafter "long disclosure") (group 3) 

Shorter version of long disclosure: "NOTICE: These testimonials do not imply that 

similar results will happen with your use of our products." (hereafter "short disclosure") 

(group 4) 

"Stronger" disclosure # 1: "NOTICE: These testimonials are based on the experiences of 

a few people. You are not likely to have similar results." (hereafter "few people") (group 

5) 

"Stronger" disclosure # 2: "NOTICE: These testimonials do not prove our product works. 

You should not expect to have similar results." (hereafter "doesn't prove") (group 6) 

The long disclosure took up four lines of text and due to its length it was more than twice as large 

as the other three disclosures, each of which took up two lines of text. 

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Results 

1. Ad Claim Recall 

Respondents were first asked two open-ended questions. They were asked what the main idea

was and what other ideas, if any, were communicated by the booklet.

Table 1 shows a tabulation of combined responses to these two questions.

Table 1

Ad Claim Recall

No 

Booklet 

(1) 

No 

Disclosure 

(2) 

Long 

Disclosure 

(3) 

Short 

Disclosure 

(4) 

"Few 

People" 

(5) 

"Doesn't 

Prove" 

(6) 

# of 

Respondents 

34 34 29 34 35 34 

Recalled a 

Breathing 

Claim 

0% 32.4% 51.7% 47.1% 40.0% 32.4% 

Recalled an 

Energy Claim 

14.7% 58.8% 69% 61.8% 68.6% 61.8% 

Recalled a Pain 

Claim 

5.9% 38.2% 48.3% 50.0% 34.3% 29.4% 

Recalled a 

Breathing, 

Energy, or Pain 

Claim 

17.6% 61.8% 82.8% 70.6% 82.9% 67.6% 

Recalled 

Disclosure 

0% 0% 0% 2.9% 0% 0% 

These results show: 

• A substantial number of respondents (62% to 83%) who were exposed to the cover letter and 

testimonial booklet (groups 2 - 6) recalled a breathing, energy, or pain relief claim.1 

Additional respondents said that the product cures or improves many or all conditions or 

diseases, without mentioning a specific health condition or disease. 

There were no significant differences between the "no disclosure" group (group 2) and 

any of the disclosure groups (groups 3 – 6) in the recall of breathing, energy or pain relief claims. 

(continued...) 

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• Virtually none of the respondents in the "no booklet" condition (group 1), who were exposed 

to the cover letter only, reported that the letter communicated breathing or pain relief claims. 

However, 15% of "no booklet" condition respondents indicated that the cover letter 

communicated an energy claim. These respondents may associate improved energy with the 

consumption of any dietary supplement. 

• Of the 132 respondents who were exposed to a disclosure (groups 3 – 6), only one respondent 

mentioned the disclosure in response to the two open-ended questions. 

2. Assessment of Efficacy 

Next, respondents were read a list of statements and were asked whether each statement had or 

had not appeared in or had been implied by the materials they had read. Respondents were also 

given the option to say "don't know" or "not sure." 

The six statements read to respondents concerned whether the advertised product reduces 

breathing problems, reduces thyroid problems, increases energy levels, reduces hair loss, relieves 

chronic or persistent pain, and reduces dry skin problems. The order for the six statements was 

rotated. Three of these statements (breathing, energy, and pain relief) focused on problems that 

were discussed in the testimonials, while the other three statements (thyroid, hair loss, and dry 

skin) focused on problems that were not discussed in the testimonials. These latter statements 

served as decoys. 

Table 2a shows the percentage of respondents who said that the claims about breathing, energy, 

and pain were made in or implied by the materials they had read: 

Table 2a

Efficacy Assessment

No 

Booklet 

(1) 

No 

Disclosure 

(2) 

Long 

Disclosure 

(3) 

Short 

Disclosure 

(4) 

"Few 

People" 

(5) 

"Doesn't 

Prove" 

(6) 

Breathing 14.7% 85.3% 89.7% 85.3% 88.6% 79.4% 

Energy 38.2% 88.2% 100% 88.2% 100% 91.2% 

Pain 17.6% 88.2% 86.2% 88.2% 77.1% 79.4% 

1

(...continued) 

However, when considering the recall of either a breathing, energy, or pain relief claim, one of 

the comparisons between the "no disclosure" group and a disclosure group was statistically 

significant --respondents in the "few people" group showed a higher recall than did respondents 

in the "no disclosure" group (83% vs. 62%, p<.05). 

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These results show: 

• In the "booklet" conditions (groups 2 – 6), more than three-quarters of the respondents agreed 

that a breathing, energy, or pain relief claim was made in or was implied by the promotional 

materials. 

• In the "no booklet" condition (group 1), from 15%-38% of the respondents agreed that a 

breathing, energy, or pain relief claim was made in or was implied by the promotional 

materials. The highest percentage (38%) was associated with the energy claim. As suggested 

earlier, respondents may associate improved energy with taking any dietary supplement. 

• None of the disclosures (groups 3 – 6) significantly reduced the percentage of respondents 

agreeing that a breathing, energy, or pain relief claim was made in or was implied by the 

promotional materials. 

To determine an "adjusted" measure of the proportion of respondents agreeing that a breathing, 

energy, or pain relief claim was made in or was implied by the promotional materials, an 

adjustment was made to account for "yea" saying or because of prior beliefs that may be 

associated with all dietary supplements. Responses to the "no booklet" condition, which had no 

specific health claims, were subtracted from responses to the "booklet" conditions to make these 

adjustments. Table 2b shows the "adjusted" responses: 

Table 2b

Efficacy Assessment (Adjusted)

No 

Disclosure 

(2) 

Long 

Disclosure 

(3) 

Short 

Disclosure 

(4) 

"Few 

People" 

(5) 

"Doesn't 

Prove" 

(6) 

Breathing 70.6% 75.0% 70.6% 73.9% 64.7% 

Energy 50.0% 61.8% 50.0% 61.8% 53.0% 

Pain 70.6% 68.6% 70.6% 59.5% 61.8% 

These results show: 

• After adjustment, between 50% and 71% of the respondents in the "no disclosure" condition 

(group 2) agreed that a breathing, energy, or pain relief claim was made in or was implied by 

the promotional materials. 

• None of the disclosures (groups 3 – 6) significantly reduced the percentage of respondents 

agreeing that a breathing, energy, or pain relief claim was made in or was implied by the 

promotional materials. 

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3. Assessment of Typicality 

Respondents who agreed that the advertised product reduces breathing problems, reduces pain, or 

increases energy levels were asked a follow-up question to assess typicality. Respondents were 

asked whether the dietary supplement improves the condition for "all," "almost all," "most," 

"about half," "some," "very few," or "none" of the people who try it. 

Table 3a shows the percentage of respondents who responded with all, almost all, most, or about 

half: 

Table 3a*

Typicality Assessment

No 

Booklet 

(1) 

No 

Disclosure 

(2) 

Long 

Disclosure 

(3) 

Short 

Disclosure 

(4) 

"Few 

People" 

(5) 

"Doesn't 

Prove" 

(6) 

Breathing 11.8% 70.6% 75.8% 70.6% 74.3% 70.6% 

Energy 29.4% 70.6% 96.5% 82.3% 85.7% 73.5% 

Pain 11.8% 79.4% 82.3% 76.5% 71.4% 67.6% 

*

Percentages are computed based on all respondents, not just those who were asked this question. 

These results show: 

• In the "booklet" conditions (groups 2 - 6), two-thirds or more of the respondents felt that the 

dietary supplement would reduce breathing problems, increase energy levels, or relieve pain 

in all, almost all, most, or about half of the people who try it. 

• In the "no booklet" condition (group 1), from 10% to 29% of respondents felt that the dietary 

supplement would reduce breathing problems, increase energy levels, or relieve pain in all, 

almost all, most, or about half of the people who try it. As with communication of product 

efficacy, the highest percentage (29%) was associated with the energy claim. 

• None of the disclosures (groups 3 – 6) significantly reduced the percentage of respondents 

who felt that the dietary supplement would reduce breathing problems, increase energy 

levels, or relieve pain in all, almost all, most, or about half of the people who try it. 

To determine an "adjusted" proportion of respondents who felt that the dietary supplement would 

reduce breathing problems, increase energy levels, and relieve pain in all, almost all, most, or 

about half of the people who try, an adjustment was made to account for "yea" saying or because 

of prior beliefs that may be associated with all dietary supplements. Table 3b shows the 

"adjusted" responses: 

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Table 3b

Typicality Assessment (Adjusted)

No 

Disclosure 

(2) 

Long 

Disclosure 

(3) 

Short 

Disclosure 

(4) 

"Few 

People" 

(5) 

"Doesn't 

Prove" 

(6) 

Breathing 58.8% 64.0% 58.8% 62.5% 58.8% 

Energy 41.2% 67.1% 52.9% 56.3% 44.1% 

Pain 67.6% 70.5% 64.7% 59.6% 55.8% 

These results show: 

• After adjustment, more than half of the respondents in the "no disclosure" condition (group 2) 

felt that the dietary supplement would reduce breathing problems or relieve pain and about 

two fifths of the respondents felt that the dietary supplement would increase energy levels in 

all, almost all, most, or about half of the people who try it. 

• None of the disclosures (groups 3 – 6) significantly reduced the percentage of respondents 

who felt that the dietary supplement would reduce breathing problems, increase energy 

levels, or relieve pain in all, almost all, most, or about half of the people who try it. 

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____________________________ 

4. Recall of Disclosure 

Finally, respondents were asked whether there was a disclaimer or notice that appeared in the 

booklet they had just read. Respondents who said "yes" were then asked what the disclaimer said 

or suggested. 

Responses are shown in Table 4: 

Table 4

Disclosure Recall

No 

Booklet 

(1) 

No 

Disclosure 

(2) 

Long 

Disclosure 

(3) 

Short 

Disclosure 

(4) 

"Few 

People" 

(5) 

"Doesn't 

Prove" 

(6) 

Respondents 

saying there 

was a 

disclosure 

23.5%2 5.9% 72.4% 44.1% 45.7% 29.4% 

"Correct" 

Recall of 

Disclosure3 

0% 0% 48.3% 35.3% 34.3% 26.5% 

These results show: 

• Percentage of respondents saying that there was a disclosure was significantly higher in the 

"long disclosure" condition (72%) as compared to the other three disclosure conditions (44%, 

46%, and 29%). 

• Between 27% to 48% of the respondents who were exposed to a disclosure (groups 3 - 6) 

correctly recalled the disclosure. 

• Although the "long disclosure" produced the highest correct recall, there were no statistically 

significant differences in the recall of the four disclosure conditions. 

2 Nearly all of the respondents in the "no booklet" condition who said there was a disclosure 

were referring to the money back guarantee that was included in the cover letter. 

3 Recall of disclosure was coded as "correct" if respondents mentioned that the results may not 

apply to everybody, that testimonials do not prove the product works, or that the manufacturer 

makes no medical claims in the booklet. 
Summary 

The results of the study indicate that: 

! In the absence of a disclosure, consumer testimonials communicated efficacy claims to a 

substantial number (over half) of consumers. 

! In the absence of a disclosure, consumer testimonials communicated typicality claims to a 

substantial number (almost half) of consumers. 

! Disclosures failed to reduce significantly communication of product efficacy claims. Also, 

disclosures were ineffective in qualifying typicality claims. 

! Over two-thirds of the respondents exposed to the "long disclosure" reported noticing the 

disclosure. By contrast, less than half of the respondents exposed to one of the other three 

disclosures reported noticing them. 

! About 1/4 to 1⁄2 of consumers recalled correctly the main idea or ideas mentioned in the 

disclosures. 

Discussion 

These results suggest that multiple testimonials about a product effectively communicate efficacy 

claims, i.e., that the product works for the uses discussed in the testimonials. Testimonials also 

appear to communicate that the product will work for all, most, or about half of the people who 

use it. Finally, the study suggests that prominent disclosures in ads containing multiple 

testimonials may be ineffective in limiting the communication of efficacy and typicality claims. 

This study used disclosures that were more prominent and stronger than the disclosures typically 

used in ads containing testimonials. For example, all the disclosures were in bold, 14-point type 

and appeared in a box. The "long disclosure" was four lines long. The two "stronger" 

disclosures stated "you are not likely to have similar results." The ineffectiveness of these 

disclosures raises the question of whether the kind of disclosures tested here may be able to 

qualify adequately efficacy and typicality claims communicated by testimonials. 

Limitations 

While this study provides potentially useful findings, several characteristics of the study may 

limit its generalizability. First, the sample consisted of only 200 dietary supplement users, with 

about 35 respondents per treatment group. Therefore, there may be differences among the groups 

that were not statistically significant because of the small sample size. Second, due to the nature 

of the product, 80% of the respondents were 60 years of age or older. Younger audiences may 

process testimonials and disclosures differently. Third, these results are based on a single 

product, i.e., a dietary supplement. The use of testimonials in the advertising for other products 

may yield different results. Finally, the study booklet contained a relatively large number of 

testimonials (18). Advertisements containing fewer testimonials may produce findings different 

than those observed in this study. 

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