Testing Tactics—Consumer vs. Scientific Language: Relating In vivo to In vitro

Editor’s note: Cosmetics & Toiletries is pleased to revive its former “Testing Tactics” column with two new columnists. Chris McLeod will focus on skin beginning in June 2013, and Trefor Evans, PhD, featured here, focuses on hair. Evans’ expertise in designing tests and interpreting results will advance the scientific understanding of hair and strengthen claims substantiation. Readers are invited to engage in this article on the Cosmetics & Toiletries' LinkedIn Group, or send comments to CTEdit@allured.com.

It should perhaps go without saying that consumer products are sold using consumer language. Market researchers and consumer scientists spend a great deal of time studying their target audience and learning this vocabulary, which subsequently allows the recounting of product benefits in the same terminology. In the hair care world, this has resulted in a long list of now well-known attributes that represent the language of the industry. Thus, R&D may receive direction from marketing colleagues to develop products that better promote “shine,” increase “strength,” tame “frizz,” or aid in any number of other familiar properties.

Upon receiving these directives involving consumer-derived words and phrases, there is a natural tendency for the product development chemist to consider the attributes from a highly scientific standpoint. Therefore, the term strength may be equated with the tensile properties of individual fibers, frizz could be associated with electrostatic buildup during grooming, and shine may be taken to relate to the interaction of light with the hair surface. As such, armed with their mission and these notions, the product developers embark on a variety of strategies in an attempt to attain their objective.

To help guide this process, a means of screening formulation iterations is desired, to determine whether strategies are on track. Since consumer testing is generally costly, in vitro instrumental testing approaches often are employed as a substitute. The hair care world has a variety of relatively well-established methodologies that are commonly used to assess and measure the technical performance of prototype formulations and finished products. For example, an instrumental combing experiment1 can be used to demonstrate how surface lubrication delivered from conditioning products is able to dramatically lower frictional forces and subsequently facilitate the grooming process (see Figure 1). Therefore, by using these approaches, formulation iterations can quickly be screened and ranked relative to benchmarks.

Perhaps not surprisingly, one frequently encounters a desire to assess the predictive capability of these methods, and validate that correlations do indeed exist between consumer and scientific testing approaches. However, these relationships can often be complex and this topic merits some discussion. In short, consumer perception of a formulation/ product is governed by a myriad of factors—not just technical functionality. For example, a conditioning product may deliver excellent lubrication and hugely facilitate grooming, but it will not be accepted by customers unless it is accomplished in an aesthetically pleasing manner.

Perceivably Superior

Many sensorial factors play no role whatsoever in technical performance but can still strongly influence consumer-perceived performance. Perhaps the most obvious of these is fragrance, where an affinity for a specific scent may halo the overall perception of a product. A thought-provoking exercise involves preparing a large batch of conditioner, then subdividing it into a series of smaller samples of which each is fragranced differently. Upon presenting these samples to consumers, it is possible to find individuals who emphatically proclaim differences in performance. Obviously, the technical performance of all samples is the same, but the allure of the scent can overwhelm other senses and influence opinion. Accordingly, it begins to become apparent as to why correlations between instrumental and overall consumer performance may not be as strong as one may hope.

However, with this said, useful insights can be obtained by comparing and contrasting differences that may arise from consumer and technical evaluations. For example, if instrumental testing suggests comparable technical performance between samples but consumer testing provides a distinct winner, then one must conclude that another overriding factor is dictating preference. This is obviously extremely valuable learning. Initially one may suspect the involvement of sensorial drivers such as fragrance, viscosity, appearance or feel-related aesthetics but there may be other subliminal factors also at work.

Consumer scientists recognize that quite different responses can be obtained for a given formulation if it is presented for panelist testing in association with a specific concept. Namely, these propositions can set up specific preconceived notions, which may or may not be realized during use. Accordingly, non-formulation-based drivers such as brand recognition, association with a specific marketing message, or possibly even the presence of a given buzzword can impact the subconscious and influence preference.

In a similar vein, one also should not neglect the potential for a similarly strong impact from an especially appealing or attractive package; how disconcerting for the formulation chemist to learn that consumers buy specific products because the bottles match the color schemes of their bathrooms. All of these factors are very real and have probably been encountered many times by seasoned product developers. Therefore, if instrumental testing indicates a prototype formula has acceptable technical performance but it does not measure up to benchmarks in consumer testing, it is likely the deficiency lies in some other area.

Lost in Translation

Now consider the reverse scenario, where an instrumental measure suggests some kind of superiority but the sample does not win in consumer testing. Again, it is clear that enhanced technical performance cannot occur at the expense of diminished aesthetics, but assuming comparable sensorial performance, the researcher potentially encounters other enlightening possibilities. Firstly, the magnitude of the technical benefit may not be sufficient to be consumer-perceivable. A second option is that the technical parameter in question actually possesses no impact on consumer judgment. This, too, can be an enormously important finding that has profound implications for future formulation strategy.

By means of illustration, consider the consumer term moisturization. Many consumers worry greatly about their hair drying out and subsequently demand products that will moisturize or hydrate. Taking these words according to their strict technical definitions, a reasonable formulation strategy may involve including known humectants in an attempt to raise the water content of hair. However, the scientific literature teaches that the water content of damaged hair is not in fact depleted in any way, and in some instances it can become slightly elevated.2 It is also well-recognized that the actual water content of hair is overwhelmingly dominated by the relative humidity (RH) of the environment, with the highest values occurring at elevated humidity (see Figure 2). Therefore, while consumers profess the desire for maximum moisturization, such high humidity conditions generally represent the very definition of a “bad hair day.”

Additional reading teaches that water is a plasticizer for hair, which subsequently lowers its tensile properties and increases the tendency for breakage.3 In short, technical evidence points to moisture being an enemy to beautiful hair. This disconnect between consumer and scientific language was convincingly demonstrated by Davis and Stofel,4 who used RH to control the water content of hair tresses before presenting them to panelists for assessment. Hair allowed to equilibrate at 80% RH contains more than four times the amount of water than it does at 15% RH—yet three out of four panelists ranked the hair stored at low humidity as feeling “more moisturized.” Similar lopsided wins were also seen for the “low humidity hair” in terms of smoothness, being less tangled and feeling less damaged.

Nevertheless, when consumers are asked whether a typical hair conditioner provides “moisturization,” the response is likely to be overwhelmingly positive. Therefore, while scientific measures show that traditional conditioners do not change actual water content, clearly a pronounced improvement in hair quality arises, which is described by consumers as moisturization. A likely explanation, again, revolves around the lubrication delivered by these products and their ability to mask the rough, course feel associated with degrading surface structure. Therefore, the alleviation of this misdiagnosed “dry” condition seemingly equates to consumer perception. Armed with this new knowledge, the formulation scientist is now likely to embark on a very different formulation strategy.

Indirect Correlation

It again must be emphasized that the list of attributes making up the industry’s vocabulary represents consumer language, and it is dangerous to assume direct relationships to technical language—even when seemingly common terms are present. This can have profound implications when it comes to crafting product claim strategies, where it is necessary to generate data that validates attractive “consumer language” stories but the primary means of accomplishing this task generally involves technical instrument-based measures.

This highlights the need to build and validate models that bridge this gap and shed light on how manipulation of hair properties is interpreted by consumers. By means of illustration, it is not a stretch to see how the ability to lubricate the hair surface could be the driver behind many consumer attributes such as conditioning, manageability, protection, smoothness and softness. However, this property can also be linked to moisturization (as described already); repair, i.e., the alleviation of sensorial negatives; strength, by reducing snags, tangles and abrasion; shine, by facilitating hair alignment; and likely others, too.

Of course, correlations cannot be expected to be perfect, as science cannot reduce a multifaceted consumer term to a single laboratory measure that is itself performed under highly controlled conditions. Indeed, the ability to perform these technical measures in such a controlled manner helps to elucidate and quantify contributions from these variables on performance. For example, it becomes evident that the manner by which the product is used, including dosage, exposure time, rinsing conditions, etc., has a significant impact on technical efficacy. Similarly, in many instances, hair type and quality can greatly influence results. Clearly consumers will use and abuse products in an almost infinite number of ways, which further contributes to a muddling of correlations.

An additional intermediary tool for helping understand these complex relationships involves the use of trained consumer panels. This approach takes some effort to set up, as it requires the recruiting and training of individuals who are able to provide an educated consumer response. Assessments are generally performed on hair tresses that can be treated and maintained under highly controlled laboratory conditions. Therefore, stronger correlations are expected between instrument performance and feedback from these skilled evaluators; but in addition, the trained assessors are also able to provide informed comments on sensorial factors associated with product treatments, i.e., did the hair feel oily, greasy, etc.?


The personal care industry is hugely complicated by the rather cryptic terms that consumers use to describe their hair and the issues that may arise. In certain instances, these words may seem to possess a technical equivalent, i.e., strength, moisturization or shine, but there is danger in taking these terms literally. For example, in general, traditional conditioners do not alter the tensile properties of hair or the water content, and they usually diminish the ability for light to reflect off the now-soiled surface of individual fibers. Nonetheless, all of the above terms regularly appear on products without much contention because consumers overwhelmingly offer positive feedback in these areas.

Therefore, in the development of products, it is important to recognize and distinguish between consumer language and scientific language, and to craft models that explain differences. Accordingly, it becomes apparent how the technical property of surface lubrication can dramatically reduce hair breakage during grooming, i.e., impart “strength”; alleviate a rough, course, “dry” feel; “moisturize”; and facilitate the ability to align hair fibers, i.e., improve shine. These conclusions are realized by comparing and contrasting information from three important resources: in vivo testing, in vitro testing and the pertinent scientific literature, which illustrates the importance of all three. Namely, the creation of successful hair care products involves the interrelationship of underlying fundamental science, an ability to deliver technical benefits, and the knowledge of how these benefits are interpreted by consumers.


Send e-mail to trefor.evans@taevans.net.

  1. TA Evans, Evaluating hair conditioning with instrumental combing, Cosm & Toil 126(8) 558–563 (2011)
  2. TA Evans, The adsorption properties of hair, in Practical Modern Hair Science, T Evans and RR Wickett, eds, Allured Business Media, Carol Stream, IL USA (2012)
  3. TA Evans, Hair breakage, in Practical Modern Hair Science, T Evans and RR Wickett, eds, Allured Business Media, Carol Stream, IL USA (2012)
  4. MG Davis and S Stoffel, Consumer perception versus single and bulk fiber technical measurements, Proc 16th International Hair Science Symposium, Weimer, Germany (2009)
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