Objective emotional assessment of tactile hair properties and their modulation by different product worlds

Objective emotional assessment of tactile hair

properties and their modulation by different product

worlds

W. Boucsein�, F. Schaefer�, M. Kefel�, P. Buschy and W. Eisfeldy�Physiological Psychology, University of Wuppertal, and yCognis Deutschland GmbH, Du« sseldorf, Germany

Received 22 November 2001, Accepted 5 December 2001

Keywords: haptic sensation, multivariate psychophysiology, product worlds, sensoryassessment, tactilehair properties

Synopsis

Tactile properties of cosmetic products constituteweak stimuli and thus can be expected to be easilymodi¢ed by mental images. In order to enhance anintended positive-emotion-inducing e¡ect of such aproduct, its experience can be embedded in a certain‘world’ that generates a positive emotional imagina-tion. The present study investigated such an in£u-ence in 12 males and 12 females, half of each beinglaymen and experts in sensory assessment. Two pro-duct worlds (emotional and technical) and three dif-ferent hair samples, two of them treated withdi¡erent shampoos and an untreated one as control,were presented to each subject in counter-balancedorder of all six combinations. An objective emotionalassessment using a psychophysiological techniquedeveloped in an earlier study was applied and com-pared with a traditional sensory assessment. Amongthe physiological measures, peripheral blood volumeand facial muscular activity were the most sensitivein revealing e¡ects of and interactions between theproduct worlds and hair samples. Amultivariate eva-luationof the physiological data revealed three discri-minant functions that explained 78.4% of the totalvariance and enabled a re-classi¢cation considerablybetter than chance. The ¢rst discriminant function

clearly separated the treated from the untreated hairsamples whichwas not possible by subjective ratingsor traditional sensoryassessment.The two other dis-criminant functions comprised a hedonistic and aproduct world factor. The emotional product worldexerted the largest in£uence in case of the weakesttactile di¡erences between the hair samples, and itsin£uencewas largeron laymenthanonexperts. Gen-der e¡ects were most prominent in the subjectivedomain. In conclusion, multivariate psychophysiolo-gical methodology is superior to traditional sensoryassessment in revealing subtle di¡erences in the tac-tile perception of cosmetic products.

Resume

Les proprie¤ te¤ s tactiles des produits cosme¤ tiques con-stituent de faibles stimuli, de sorte que l’on peuts’attendre a' ce qu’elles soient facilement modi¢e¤ espar des images mentales. A¢n d’intensi¢er l’e¡etintentionnellement incitant a' une e¤ motion positiveenvers un tel produit, son expe¤ rience peut e“ tre intro-duite dans uncertain‘environnement’qui engendrer-ait une imagination e¤ motionelle positive.La pre¤ sente e¤ tude a teste¤ telle in£uence sur 12

hommes et 12 femmes, la moitie¤ de chaque groupee¤ tant noninitie¤ e et l’autre experte en e¤ valuation sen-sorielle. Nous avons pre¤ sente¤ a' chaque sujet, parordre contrebalance¤ des six possibilite¤ s, deux ‘envir-onnements’du produit (e¤ motif et technique), et troisdi¡e¤ rents e¤ chantillons capillaires dont deux ou' lescheveux e¤ taient traite¤ s par di¡e¤ rents shampooings,et, pour le contro“ le, un e¤ chantillon de cheveux

International Journal of Cosmetic Science, 2002, 24, 135^150

� 2002 Blackwell Science Ltd 135

Correspondence: Physiological Psychology, University ofWuppertal, Max-Horkheimer-Str. 20, D-42119 Wuppertal,Germany.Tel:þ49 202 439 2338, fax:þ49 202 4392926.Co-correspondence address: Cognis Deutschland GmbH,Henkelstr. 67, D-40589 Du« sseldorf, Germany; Tel:þ492117940 4628, fax: þ49 2117981087.

nontraite¤ s. Nous avons employe¤ une e¤ valuation e¤ mo-tionelle objective par une technique psychophysiolo-gique de¤ veloppe¤ e durant une e¤ tude pre¤ ce¤ dente etl’avons compare¤ e a' une e¤ valuation sensorielle tradi-tionnelle. Parmi les mesures physiologiques, levolume sanguin pe¤ riphe¤ rique et les activite¤ s desmuscles faciaux e¤ taient exceptionnellement sensi-bles a' manifester les e¡ets des ‘environnements’ duproduit, et des e¤ chantillons, ainsi que les interactionsentre eux.Une e¤ valuation multivariante des donne¤ es physio-

logiques de¤ voila trois fonctions discriminantes expli-quant les 78.4% de l’ensemble de la variance, etpermettant une re-classi¢cation conside¤ rablementmeilleure que le hasard. La premie' re fonction discri-minante a nettement distingue¤ les e¤ chantillons decheveux traite¤ s de ceux nontraite¤ s; ce qui n’e¤ taitpas possible a' travers une e¤ valuation subjective oudes mesures sensorielles traditionnelles. Les deuxautres fonctions discriminantes comportaient unfacteur he¤ doniste et d’environnement du produit.Dans le cas des plus faibles di¡e¤ rences tactilesentre les e¤ chantillons capillaires, l’environnemente¤ motif du produit a exerce¤ plus d’in£uence sur lesnoninitie¤ s que sur les experts. Les e¡ets du genrehumain e¤ taient surtout marquants dans le domainesubjectif.En conclusion, pour de¤ voiler les subtiles di¡e¤ r-

ences dans la perception tactile des produitscosme¤ tiques, la me¤ thodologie psychophysiologiquemultivariante est supe¤ rieure a' l’e¤ valuation sensor-ielle traditionnelle.

Introduction

There is a distinct shift in our encounter with exter-nal matters. In many cases, we are not a¡ected bythe external object itself but by the stimuli which ¢reour imagination.Thus, above all, the encounterwiththe object takes place in our brains. This is not at allsurprising, as according to Aristotle ‘the soul neverthinks without a mental image’. Expressed in moremodernterms: imagination is anessential part of per-ception at any level.For example, our vision is only half of the seeing

process.The eye does not send the image to the brain;the brain imagines the image and thena dialog startswith the eye until the two of them reach agreement.The image was never in the eye; it was always in thebrain. The brain veri¢es the image, it does not gener-ate it [1]. This can be assumed to be more or less truefor all of our sensorycapabilities including the tactile

sensation that is involved in the handling of cosmeticproducts.Our tactile sensation seems to be particularly

dependent on the mental images. For that reason, wecharacterize our tactile experiences with the word‘like’: it feels like velvet, silk, or sandpaper. Thus, wegenerate inner images which help us to recognizethe object we touch. Taking into consideration thespeci¢c process of our sensory perception, onewouldexpect that images generated in our brain stronglyin£uence the quality of our experiences. There arenumerous possibilities to generate such an innerimage: showing pictures (e.g. videos), embracing uswith theworld of music, or just telling stories.The lat-ter is at present a hot issue, because business counse-lors claim that story-telling will be the key motivatorfor purchasing products.The in£uence of the imaginative world on tactile

sensations is shown in this paper by means of objec-tive testing. It has been demonstrated in an earlierstudy [2] that di¡erent kinds of foams could be suc-cessfully distinguished in a double blind investiga-tion by a newly developed technique called objectiveemotional assessment (OEA). Other than by meansof a traditional sensory assessment [3], OEAwas notonly able to di¡erentiate the physical properties ofthe foams but also to reveal their emotion-inducingproperties that could not be assessed by the tradi-tional technique.The use of OEAcomprises both subjective and phy-

siological measures. The so-called psychophysiologi-cal responses (e.g. changes in heart rate, peripheralblood volume, skin conductance or facial muscularactivity) are elicited by the phylogenetically olderparts of the human brain, especially the limbic sys-tem. The detection of these prior-to-consciousnessemotion-driven responses is of great interest for aproper understanding of the acceptance or refusal ofproducts byconsumers. Inmany instances, decisionstobuyor not tobuyaproduct arenot rationallybased.Instead, they originate from non-conscious imagesin our brain. Therefore, sensory assessment of pro-ducts has become an interdisciplinary topic, includ-ing not only chemists and physicists but alsophysiologists and psychologists [4]. Psychophysiolog-ical measures do not only re£ect an immediate emo-tional response to a product during an initialcontact or a manipulation phase, as shown by [2].Their additional advantage over verbal descriptionssuch as used in the traditional sensory assessment isthat they cannot be easily faked. Thus, they consti-tute an objective measure of what is taking place

Emotional assessment of tactile hair properties and their modulation W. Boucsein et al.

136 � 2002 International Journal of Cosmetic Science, 24, 135^150

during the interaction of the tactile stimulation by aproduct and the inner images in our mind.In the realm of product testing, such inner images

are normally created by a context not directly refer-ring to the properties of the product itself. Instead,these ‘worlds’constitute an induction of an imagina-tion with the aim of linking the positive emotions tothe product in question. This is of particular impor-tance for the tactile properties of cosmetic productsthat constitute ratherweak stimuli compared to opti-cal and acoustical stimulation.Therefore, we decidedtouse a certainproductworld inorder to induce posi-tive emotions prior to the subjects’contact with thetactile stimuli. For the study presented in this paper,we thus prepared two di¡erent product worlds, anemotional one and, for reason of contrast, a nonemo-tional (technical) one. The products tested here werea special hair shampoo containing a nanoparticularlayer silicate (Optigel1SH, Su« d-Chemie) and a simplestandard shampoowithout this silicate, both appliedto standard hair samples. An untreated hair samplewas used as standard for comparison.Because of the huge individual di¡erences to be

expected in this type of consumer research [cf. 5],and because there are considerable gender di¡er-ences in emotion [see 6], we decided to use bothmaleand female subjects and introduce gender as a sepa-rate factor in our design. Because cosmetic productsare normally assessed by experts [e.g. 3], althoughthe product aims to na|« ve users, both experts and lay-men were tested in the present study in order todetect whether experts from the producer’s companywill show a bias in their product assessment asdescribed by [7].A major goal of the present study was, however, to

probe themultivariate psychophysiological approachintactile stimulationbyhair samples treatedwith dif-ferent cosmetic products. Single physiological mea-sures such as electrodermal activity (sometimesbetter known as galvanic skin response) or facial

muscle activity have already been successfully usedinproduct testing [e.g.8,9]. However, each physiolog-ical measure can only re£ect one speci¢c aspect ofthe psychophysiological response [10]. Therefore, weattempted to apply the multivariate approach inOEAas used in a pilot study on tactile stimuli [2] andextend it bymultivariate testing suchas discriminantanalysis, in order to see to what extent the relativelysmall di¡erences in tactile stimulation produced bycosmetic treatment of hair can be statistically pro-ven.

Materials and methods

Hair samples and product worlds

Three kinds of hair samples were used in the presentstudy, di¡ering in their treatment. Hair tresses of18 cm length and 2 g weight (Alkinco Type 6634)were cleaned for 30 minwith a12% lauryl ether sul-phate (Texapon1NSO, Cognis) solution (pH ¼ 6.5)and rinsed for 5 min. Thereafter, the hair tresseswere either left untreated (control sample) or treatedwithone of the products described inTable I. For eachtreatment,0.5 g of the product was applied to1 g hairfor 5 min and rinsed for1min. Finally, the hair tres-ses were dried. Each hair tress was used for one trialonly, in order to prevent possible changes caused bycontact andmanipulationwith the subjects’ hands.As additional experimental conditions, two di¡er-

ent product worlds were created in the form of videoclips, comparable to a TVcommercial. The video clipwith the emotional product world used scenes fromtravel documentation movies on the Cape VerdeIslands, the Dominican Republic and Hawaii andcontained short sequences showing hair (i.e. awoman shaking her long hair at the beach) in anemotionally positive holiday context (i.e. surfers,palm trees, white sand). The acoustical backgroundfor the emotional video clip was taken from the song

Table I Formulations of the twoshampoos for hair sample treatment(%) Ingredients

Standard

shampoo

Silicate

shampoo

Lauryl ether sulphate (Texapon1NSO) 43.00 43.00

Cocamidopropyl betaine (Tego1Betain F50) 7.00 7.00

Sodium magnesium silicate (Optigel1SH) – 0.50

Preservative (Euxyl1K 100) 0.20 0.20

Salt (NaCl) 4.00 4.00

Water ad 100 ad 100

pH value 7.09 7.09


� 2002 International Journal of Cosmetic Science, 24, 135^150 137

‘Return to innocence’of the band ‘Enigma’. The dura-tion of the clips was 40 s. Each clip contained sixscenes. Three versions of each video clip were pre-pared, containing the same scenes but in counter-balanced sequences. They were applied for the threedi¡erent hair samples tested in the same session.The videomaterial for the technical product world

was taken from scienti¢c ¢lms about physical hairproperties and respective test methods. The ¢nalvideo clip for the technical world showed the struc-ture of the skin including hair roots, automaticcombing and statistical diagrams. The acousticalbackground was taken from the song ‘Oxygene’ fromJean Michel Jarre. As with the emotional clip, threedi¡erent versions of the technical clip were preparedbycounter-balancing the sequences.Anadditional neutral video clipwas produced, hav-

ing the same length as the other two clips but only inone version. The content was taken from movies ondi¡erent landscapes. No soundtrack was provided.Theneutralvideowasused for thepractice trialonly.

Design and subjects

Three di¡erent hair samples were presented follow-ing two di¡erent product world settings, each in awithin-subjects design. Twenty-four paid subjects(12 males,12 females) participated in the study. Halfof the subjects of each gender were experts in tradi-tional sensory assessment while the other halfwere laymen. All of them were chemical industryemployees at Du« sseldorf. The study was performed

in a temperature- and humidity-controlled labora-tory (22 8C, 40% RH). The samples were hair tresseseither (1) untreated (as control condition), or (2) trea-ted with a standard shampoo, or (3) treated with aspecial shampoo containing a nanoparticular sili-cate layer (Optigel1SH, Su« dchemie, cf. exact formu-lation in Table I). The product worlds were either (1)emotional or (2) technical, each applied to the threehair samples in each sequence equally often in eachsubgroup. The presentation of the resulting sixexperimental conditions was fully counter-balancedover the six subjects in each gender/expert-subgroupbymeans of a Latin square design.The experimenters were a male psychophysiology

student (the third author) and a female technicalassistant. The psychophysiologists engaged in thestudy were not informed about the pretreatment ofthe hair samples and the results of their sensoryassessment until the interpretationof thepsychophy-siological results was ¢nished. Thus, the study wasperformed as a double-blind investigation withrespect to hair samples.

Procedure

At the beginning of each session and after attachingthe electrodes, a full practice trial with an untreatedhair sample was applied for which the neutral videoclip was used (landscapes without sound). The sub-jects were seated in front of a camou£age preventingthem from visual contact with the hair samples (foran illustration, see Fig. 1 in [2]). Their left-arm was

Figure1 During the contact phase,the hair sample is pneumaticallylifted through the closed gap betweenindex- andmiddle-¢nger.



put through an opening in the camou£age to allowfor contact and manipulation with the hair samples.The hair tresses were brought toward the volunteer’shand via a pneumatic linear drive. The subjects woreheadsets to prevent them from hearing the pneu-matic mechanism which could have produced audi-tory orienting response artifacts in the physiologicalmeasures.The presentation of the six experimental condi-

tions was organized in the following way: ¢rstly, thevideo clip with the product world was presented for40 s, thereafter, the subject was instructed to spreadwide the index- andmiddle ¢ngerof his/her left hand;the hair sample was placed between these ¢ngers bythe pneumatic mechanism, followed by the instruc-tion to close the gap between the ¢ngers (Fig. 1); thehair sample was pneumatically lifted and pulledthrough the ¢ngers, constituting the contact phase;the subject was then instructed to turn his/her handto manipulate with the hair sample for 30 s (Fig. 2),constituting the manipulation phase. The procedurewas terminated with a subjective assessment andrepeated for each of the subsequent conditions.After ¢nishing each trial, the subjects rated the

subjective, hedonistic qualities of the hair sample ona 23-item Likert-type adjective checklist. All instruc-tions were presented on the video screen.Thereafter,a short pause of one minute duration was insertedbefore the next trial started. Each sessionwas termi-nated by detachment of electrodes and debrie¢ngthe subject. The duration of each session was about1h and15 min.

In order to compare the psychophysiological mea-surements with results from the subjective testmeth-ods which are already established, a sensoryassessment was performedwith10 experts followingthese experiments, using the same hair samples, theresults of which are shown in Fig. 10.

Physiological and subjective measures

The same physiological measures were taken as inthe earlier study [2]. The ¢rst group of measuresre£ected the activity of the autonomic nervous sys-tem. Electrodermal activity (EDA) was recorded fromthenar/hypothenar sites at the right palm as skinconductance, using a constant voltage of 0.5 Vapplied via 6 mm diameter sintered silver/silverchloride electrodes ¢lled with an isotonic jelly madefrom Unibase [11, p. 108]. Peripheral blood volumewas recorded as ¢nger pulse volume by means of aninfrared photoplethysmographic coupler from thetip of the right middle ¢nger. The electrocardiogram(EKG) was recorded via two electrodes between thesternum and the bottom of the left rib cage, with aground electrode on the right forearm.The second group of measures re£ected the activ-

ity of the somatomotor system resulting in facialexpressions. The electromyographic activity (EMG)of three facial muscles was recorded by means of3 mm silver/silver chloride electrodes ¢lled with ahighly conductive jelly. Before attaching these elec-trodes, the skin was prepared with alcohol in orderto lower the skin-electrode resistance to 5^10 kO,

Figure 2 During the manipulationphase, the subject feels the hair sam-ple with his/her hand.



which was veri¢ed for each electrode site with anohmmeter. The facial muscles recorded were thezygomaticus major (pulls the lip corner up), the leva-tor labii superioris (raises the upper lip, widens nos-trils), and the corrugator supercilii (knits the brow).The electrode sites were chosen according to [12].All physiological recordings were made by means

of a med-Natic system, digitized by an analogue-digital converting board and stored on a computerhard disk for o¡-line evaluation.The subjective ratings were obtained by showing

the item in question to the subjects in front of thecamou£age. The subject verbally expressed his/herresponse as ‘not at all’, ‘a little’, ‘considerably’, or‘strong’. These verbal responses were scored asLikert-scale values1^4.The 23 items (see Fig. 5)weretaken fromanadjective checklist [13] and froma sen-sory assessment inventory [3] that had been adaptedfor the use in hair sample assessment.

Evaluation and interpretation of thepsychophysiological measures

For each hair sample, a contact phase and amanipu-lation phase was evaluatedwith 30-s duration each.Two di¡erent types of EDAparameters were evalu-

ated: the frequency of non-speci¢c skin conductancereactions (NS.SCR frequency) and the mean ampli-tude of all skin conductance reactions (in mS) for theinterval in question. The NS.SCR frequency is a validindicator of emotional excitement, responding easierto negative as compared to positive emotional quali-ties [see 11, pp. 277^284]. The mean SCR amplitudecan be interpreted as an indicator of persisting unfa-miliarity with the product quality during the 30-speriods of contact or handling [see 2].A decrease of the peripheral blood volume is

regarded as an indicator of an orienting responsebeing independent of the emotional valence of agiven stimulus [14]. For the evaluation in the presentstudy, the mean pulse volume amplitude (PVA) wascalculated. Inaddition, the degree of PVAmodulationwas chosen as parameter, calculated as variationcoe⁄cient (i.e. the standard deviation of the PVAamplitudes per heart cycle divided by the mean PVAamplitudes in this interval). An increase of the PVAmodulation can be interpreted as indicating orient-ing response eliciting properties of the productwhichraise interest in its characteristics [see 2].From the EKG, four di¡erent parameters were

extracted: ¢rst the mean heart rate (HR), expressedin milliseconds, because it refers to the interbeat

interval (IBI). An increase of HR deceleration (i.e. anincrease in the IBI maximum) indicates an increas-ing orienting response [15].Therefore, the maximumand theminimum IBIobtained inthe 30-s evaluationperiod were obtained as the second and third para-meters. The fourth parameter was heart-rate vari-ability (HRV), calculated as root mean square ofsuccessive di¡erences (RMSSD) from IBIs. A decreaseof HRV is a valid indicator of mental strain [see16]. Ifa HRV decrease appears during the contact orthe manipulation phase, it can be inferred that thehair sample under investigation is highly complex,thus requiring an increased amount of cognitiveprocessing.Facial EMG recordings were recti¢ed and inte-

grated. From this signal, the EMG activity (in mV)was calculated by summing up the amplitudes dur-ing the 30 s evaluation periods. An increase of thezygomaticus activitycan be interpreted as indicatinga positively tuned emotion elicited by the hair sam-ple, whereas an increase in the levator labii activitypoints to a negatively tuned emotion or an irritationduring a confrontation with unusual stimulusmaterial. An increase of the corrugator activity indi-cates a critical evaluation of the hair sample inquestion.

Statistical evaluation

Univariate analyses of variance were applied tophysiological and subjective data, with three hairsamples and two product worlds as repeated mea-surements factors, and gender as well as expertise inatraditional sensoryassessmentas between-subjectsfactors, bothwith two steps. Degrees of freedomwerecorrected by Greenhouse^Geisser’s Epsilon.Additionally, physiological and subjective data sets

were separately subjected to multivariate analysesby means of discriminant analysis. In order to ful¢lthe requirement of independent samples, the portionof variance owing to the individual response di¡er-ences and that owing to the di¡erent sequences ofhair sample and product world combinationswere eliminated by means of matrix transformation,using a procedure that has been developed in the¢rst author’s laboratory [17]. Eigen values, Wilk’sLambda, and the amount of correct re-classi¢cationinto the six groups (hair samples by product worlds)were used as criteria of ¢t for the discriminantanalyses.Finally, theweights of the group centroids from the

physiological discriminant analysis were correlated



with the subjective data, in order to facilitate theinterpretation of the physiological discriminantfunctions. All statistical analyses were performed bySPSS 7.0 [18].

Results

This section ¢rst reports themain e¡ects and interac-tions of the within-subjects factors (i.e. hair samplesand product worlds) from both univariate and multi-variate analyses. Thereafter, e¡ects of the between-subjects factors (i.e. expertise and gender) will bereported.

Measures of the autonomic nervous system

Both EDA measures (NS.SCR frequency and meanSCR amplitude), all EKG derived measures, and thePVA amplitude did not reveal any signi¢cant e¡ectsfor thewithin-subjects factors (hair samples andpro-duct worlds) in the univariate analyses. During thecontact phase, the interaction between hair samplesand product worlds became highly signi¢cant (F2/19¼ 7.63, P < 0.01) for the degree of PVA modulation.As can be inferred from Fig. 3, the untreated (control)hair sample elicited a larger PVA modulation in theemotional as compared to the technical world. Thise¡ect was reversed for the standard-shampoo-treated hair sample and not present for the silicate-shampoo-treated sample.The same PVA modulation pattern appeared dur-

ing the manipulation phase, where the interactione¡ect, however, only approached signi¢cance (F2/19¼ 3.19, P ¼ 0.06).

Measures of facial muscle activity

Although the univariate analyses of the EMGrevealed very few signi¢cances, Fig. 4 will give anoverview for the results of all three facial muscles inthe two recording phases, because a clear patternemerged.During the contact phase, the standard-shampoo

hair sample elicited greater activities in the technicalcompared to the emotionalworld for the zygomaticusand the levator labii (F2/19 ¼3.29, P ¼ 0.06), whereasthe corrugator was signi¢cantly more active in thetechnical world, regardless of the hair sample inquestion (F1/20 ¼5.12, P < 0.05).This e¡ect seemed to reverse during themanipula-

tion phase (right panel of Fig. 4), where the facialmuscle activity appeared generally larger in theemotional as compared to the technical worldbut approached signi¢cance only for the levator labii(F1/20 ¼3.99, P ¼ 0.06). No signi¢cant interactionsbetween the two within-subjects factors were foundfor EMGmeasures.

Subjective ratings

The main e¡ects of the two di¡erent product worldson the subjective ratings of the hair samples areshown in Fig. 5. The items are grouped accordingto their preference in each world; the ones thatyielded higher ratings in the emotional world areshown ¢rst. There was only one marginally signif-icant main e¡ect of hair samples (‘smooth’) and twointeractions between hair samples and productworlds approaching signi¢cance (‘pleasant’ and‘voluminous’).

Figure 3 PVAmodulation (%) underall 6 experimental conditions duringthe contact phase.



The discriminant analysis performed with all 23items of the subjective ratings did not reveal a signif-icant result (Wilk’s Lambda ¼ 0.439, d.f. ¼115,P ¼ 0.722 for the ¢rst ¢ve discriminant functions).The total amount of correct re-classi¢ed cases intothe six experimental conditions was 40.7%.

Multivariate analysis of physiological measures

Five discriminant functions were calculated, re-vealing a marginally signi¢cant result (Wilk’sLambda ¼ 0.298, d.f. ¼130, P ¼ 0.075). In order toobtainthephysiological parameterswith thegreatestdiscriminative power, stepwise discriminant ana-lyses were performed, revealing 10 variables (¢vefrom the contact and ¢ve from the manipulationphase), the multivariate combination of which gave

the best discriminative power for the ¢rst three dis-criminant functions (see Table II). The amount oftotal variance explainedwas 78.4%.Table III shows the result of the re-classi¢cation of

the six experimental conditions when using the 10physiological measures and the three discriminantfunctions. The total amount of correct re-classi¢edcases was 47.2% which is considerably better thanchance (16.7%).Figure 6 shows the projections of the group cen-

troids for six experimental conditions (three hairsamples combined with two worlds) on the threeplanes spread by each combination of two discrimi-nant functions.Table IV shows the signi¢cant correlations

between discriminant functions two and three anditems of the subjective rating scale. Because there

Figure 4 EMG (mV) from the threefacial muscles under all 6 experimen-tal conditions during contact andmanipulation phase.



were no signi¢cant correlations with the weights ofdiscriminant factor 1, the two highest correlationswere reported instead.As can be inferred from Fig. 6, function1 discrimi-

nates between the control condition and thetwo treatments (standard or silicate shampoo).Function 2 re£ects the e¡ects of the two productworlds on the hair samples. Interestingly, the in£u-ence of the emotional world di¡ered in its directionfor the standard-shampoo treatment on one

hand versus the silicate-shampoo treatment and theuntreated (control) hair on the other hand. In con-trast, on function 3 the in£uence of the productworlds was in the same direction for the three hairsamples.

E¡ects of expertise

Experts showed a signi¢cantly lower NS.SCR fre-quency during manipulation compared to laymen

Figure 5 Di¡erences in the subjec-tive ratings between the technical(dark grey) and the emotional productworld (light grey).Signi¢cance: ��P < 0.01; �P < 0.05;(�)P < 0.10.



(F1/20 ¼ 6.37, P < 0.05). An additional signi¢cant tri-ple interaction hair samples � product worlds �expertise appeared (F2/19 ¼5.31,P < 0.05) that is illu-strated in Fig.7.As Fig.7 shows, laymen get more excited during

the manipulationwith the treated hair samples com-pared to the control sample, however, only in theemotionalworld. Contrarily, experts get more excitedduring themanipulationwith both treated hair sam-ples inthe technicalworldwhich theyaremore famil-iar with.Experts showed a marginally signi¢cant higher

mean PVA amplitude compared to laymen duringthe contact phase (F1/20 ¼ 4.18, P ¼ 0.054). In

addition, the triple interaction hair samples � pro-duct worlds � expertise became signi¢cant (F2/19¼ 5.21, P < 0.05).As can be inferred from Fig. 8, experts show more

orienting responses (i.e. higher PVAamplitudes) thanlaymen, especially during their ¢rst contact with theuntreated hair sample, whereas laymen display nonoticeable di¡erences between the conditions at all.The higher PVA amplitudes in experts reach signi¢-cance during the manipulation phase (F1/20 ¼ 4.47,P < 0.05). Additionally, the interaction hair sam-ple � expertise becomes signi¢cant (F2/19 ¼3.55,P < 0.05): The di¡erence in the PVA amplitudes ishighest for the standard-shampoo hair sample

Discriminant functions

Physiological measures Recording period 1 2 3

IBI maximum During contact 1.533 –0.624 –0.315

PVA modulation During contact –0.078 0.572 –0.073

SCR amplitude sums During manipulation –0.326 –0.070 0.322

EMG levator labii During contact 0.737 –0.182 –0.192

EMG levator labii During manipulation –0.248 0.443 –0.556

EMG corrugator During contact –0.297 –0.197 0.502

IBI standard deviation During manipulation 0.535 0.331 –0.152

PVA modulation During manipulation –0.058 0.271 0.537

EMG zygomaticus During contact –0.374 0.414 0.288

NS.SCR frequency During manipulation –0.277 –0.232 –0.294

Eigen values 0.446 0.361 0.288

Percent explained variance 31.9 25.9 20.6

Percent cumulative variance 31.9 57.8 78.4

Coefficients exceeding absolute values of 0.400 are highlighted and will be interpreted.

Table II Standardized canonical dis-criminant function coe⁄cients of the¢rst three functions with the 10 mostdiscriminating physiological mea-sures (ordered bydecreasing discrimi-nant power)

Re-classified cases

Original cases E-Ctr E–Std E-Sil T–Ctr T–Std T–Sil Total cases

E-Ctr 16 2 2 2 2 0 24

E–Std 3 14 2 2 1 2 24

E-Sil 1 5 10 2 2 4 24

T–Ctr 3 4 2 11 1 3 24

T–Std 2 3 5 3 7 4 24

T–Sil 1 2 4 3 4 10 24

Abbreviations: E: emotional product world, T: technical product world. Ctr: control

(untreated), Std: standard shampoo, Sil: silicate shampoo hair samples. Correctly re-clas-

sified cases are highlighted.

Table III Results of the re-classi¢ca-tion by means of the three discrimi-nant functions



and lowest for the sample treated with the silicateshampoo.Figure 9 illustrates the marginally signi¢cant hair

samples � expertise interaction for the zygomaticusEMG (F2/19 ¼3.09, P ¼ 0.069). Laymen increase theirzygomaticus activity during their ¢rst contact withboth treated hair samples in comparison to theuntreated (control) hair sample, whereas experts donot show such a di¡erence.In the subjective domain, laymen rated all hair

samples in both worlds as more ‘active’, more ‘cheer-ful’, more‘interesting’, more‘voluminous’but also less‘thick’ (seeTable V). Experts rated all hair samples asmore ‘dry’ in the emotional product world comparedto laymen but only for the untreated hair sample inthe technical product world. They also rated theuntreated and the standard-shampoo sample asmore ‘brittle’ in the emotional world.While expertsrated all hair samples in both worlds as equally‘pleasant’, laymen rated the untreatedand the silicateshampoo-treated sample as more ‘pleasant’ in theemotional world but the standard shampoo-treatedhair sample as most ‘pleasant’ in the technical pro-duct world.

E¡ects of gender

Thewell-known gender di¡erence in HR (i.e. femaleshaving a higher HR) became signi¢cant in both thecontact and the manipulation phase (F1/20 ¼ 4.84and 5.75, P < 0.05). In addition, the gender � hairsample interaction reached signi¢cance for the stan-dard deviation of IBIs (a HRV index) in the contactphase (F2/19 ¼5.97, P < 0.05). Males showed a higherHRV than females for the silicate-shampoo-treatedhair sample, while the reverse e¡ect appeared for theother two hair samples.Males ratedall hair samples inbothproductworlds

as signi¢cantly more ‘voluminous’ compared tofemales (F1/20 ¼8.70,P < 0.01). Interactionsbetweengender and product world reached signi¢cance for‘dull’ (F1/20 ¼ 8.86, P < 0.01) and ‘pleasant’ (F1/20 ¼ 4.45, P < 0.05). Females rated all hair samplesin the technical world as more ‘dull’ than males;the reverse was true for the emotional productworld. Males did not di¡er in their ratings of ‘plea-sant’ in bothworlds, while females rated all hair sam-ples as more ‘pleasant’ in the emotional productworld.

Figure 6 Projections of the group centroids for the sixexperimental conditions onthe three possible combinationsof discriminant functions. Abbreviations: E: emotional pro-duct world; T: technical product world; Ctr: control; Std:standard shampoo; Sil: silicate shampoo hair samples. Foreach hair sample, changes from the technical to the emo-tional product world are indicated byarrows (!).



Item Function 1 Function 2 Function 3

Loaded r ¼ –0.386, P ¼ 0.45

Neat r ¼ 0.460, P ¼ 0.36 r ¼ 0.831, P < 0.05

Smooth r ¼ –0.908, P < 0.05

Voluminous r ¼ 0.957, P < 0.01

Pleasant r ¼ 0.943, P < 0.01

Sluggish r ¼ –0.903, P < 0.05

Warm r ¼ –0.869, P < 0.05

Dull r ¼ 0.874, P < 0.05

Lacking energy r ¼ 0.865, P < 0.05

Table IV Signi¢cant (or highest incase of function1) correlationof groupcentroids from the discriminant func-tions with means of the subjectiveitems over all six experimental condi-tions

Figure 7 NS.SCR frequency (min^1)for experts (solid line) and laymen(dashed line) under all six experimen-tal conditions during the manipula-tion phase.

Figure 8 PVA amplitudes (in arbi-trary units) for experts (solid line)and laymen (dashed line) under allsix experimental conditions duringthe contact phase.



TableV Signi¢cant e¡ects of expertise on subjective ratings

Item F d.f. P Effect

Active 14.50 2/19 < 0.01 Main effect of expertise

Cheerful 10.74 2/19 < 0.01 Main effect of expertise

Interesting 5.11 2/19 < 0.05 Main effect of expertise

Voluminous 10.04 2/19 < 0.01 Main effect of expertise

Thick 6.89 2/19 < 0.05 Main effect of expertise

Dry 6.61 1/20 < 0.05 Interaction expertise � product world

Brittle 5.06 1/20 < 0.05 Interaction expertise � product world

Pleasant 4.06 2/19 < 0.05 Triple interaction expertise � product world � hair sample

Figure 9 Zygomaticus EMG (in mV)for experts (solid line) and laymen(dashed line) under the three hairsample treatment conditions.

Figure10 Sensoryassessment of thethree hair samples. Zero referenceline: untreated hair (control), blackline: standard shampoo; and light-grey line: silicate shampoo. Positivechanges are displayed towards 0.5,negative changes towards ^0.5.



Discussion

Hair samples do not constitute strong stimuli for eli-citingpsychophysiological responses suchas electro-dermal activity and heart rate changes. Instead,only ¢ne-grained analyses of special emotion-relatedphysiological measures such as peripheral bloodvolume, PVA modulation or facial muscle activityhave theproperty to reveal physiological e¡ects of dif-ferent hair sample treatments and their interactionswith product worlds as probed in the present study.Furthermore, di¡erences in PVA modulation whichcanbe regardedas anobjective indicator for the inter-est raised by the product in question, approach statis-tical signi¢cance only in the contextual frame workof the di¡erent productworlds applied beforepresent-ing the hair samples. The untreated hair sampleraised more interest in the emotional compared tothe technical world, an e¡ect that is reversed for thestandard shampoo hair sample and not present forthe silicate shampoo sample (Fig. 3). From a psycho-physiological point of view, there might be a ratherspeci¢c property of the PVA to reveal di¡erences intactile orientation because it constitutes a measureof blood supply in the ¢nger tips.At ¢rst glance, suchapositive in£uence of the tech-

nical product world on the standard shampoo hairsample can be seen in the zygomaticus activity dur-ing the contact phase which is reversed duringmanipulationwith thehair tress (Fig. 4, upperpanel).However, the levator labii which lifts the nostrils andeven the corrugator which knits the brows show avery similar pattern, including the reversion duringmanipulation (Fig. 4,middle and lower panel).There-fore, the activity in single facial muscles can not beinterpreted as straight forward as was the case withfoams that constitute stronger tactile stimuli thanhair samples [cf. 2]. Instead, the more generalizedpattern of facial EMGs re£ects a general uncertaintyof our subjects with respect to the emotion inducingproperties of the stimuli applied in the present study.Despite the ratherweake¡ects of ourexperimental

conditions on single physiological measures, theirevaluation by means of multivariate discriminantanalysis reveal a clear pattern for the action of thetwo product worlds on the three hair samples usedhere (Fig. 6).The ¢rst discriminant function can be interpreted

as a purely physiologically determined factor,because its group centroids do not show any signi¢-cant correlation with subjective rating which theother two functions do (Table IV). The emergence of

function1that separates the controlhair sample fromthe two treated samples (see upper panel of Fig. 6)demonstrates the advantage of OEAovera traditionalsensory assessment or any kind of purely subjectiveproduct rating. As can be inferred from Table II, the¢rst discriminant function re£ects a strong orientingresponse component during the ¢rst contactexpressed by the excessiveweight of theHR decelera-tion (IBI maximum). The second highest weight iscontributed by the levator labii during contact, indi-cating an irritation elicited by unusual stimuli. Dur-ing manipulation, a decrease in HRV (measured asIBI standard deviation) points to a component of anincreased amount of information processing. Thus,the three most contributing measures identify the¢rst discriminant function as re£ecting the degree ofunfamiliarity with the hair samples, or ‘treated’ ver-sus ‘natural’.Table II further reveals that the second discrimi-

nant function re£ects a considerable lack of anorienting component, as can be inferred from thenegative weight in HR deceleration (IBI maximum).However, thehighest positiveweight reveals an inter-est-eliciting component. The next highest weightappears in the levator labii duringmanipulation, pre-sumably owing to the rather generalized facial EMGpattern discussed earlier. The zygomaticus exerts asimilarweight duringcontactwhich is a clear indica-tor for hedonistic properties of the stimuli in ques-tion. Therefore, together with the high correlationsof the group centroids with the subjective evaluationas ‘voluminous’, ‘pleasant’, and ‘neat’ (Table IV), thesecond discriminant functioncanbeunambiguouslyinterpreted as re£ecting the valence (i.e. positive vs.negative hedonistic value) of the hair samples. Inter-estingly, as Table IV shows, ‘smooth’ constitutes anitem for negative rather than positive hedonisticvalue of a hair sample, because it is negatively corre-lated with function 2.As can be inferred from the lower two panels of

Fig. 6, the third discriminant function clearly sepa-rates the technical from the emotional productworld.The two highest positive weights are obtained by thecorrugator during contact and the PVA modulationduring manipulation (Table II), indicating a persist-ing critical evaluation that requires increased cogni-tive processing. The negative weight of the levatorlabii during manipulation underlines the positiveemotional component of function 3. Together withthe high positive correlations of the group centroidsin this factor with ‘dull’ and ‘lacking energy’ andthe negative correlation with ‘warm’ (Table IV), this



discriminant function can be interpreted as re£ect-ing the in£uence of the positive emotional setting asinduced by the emotional product world, clear-headed in contrast to the evaluative setting of thetechnical product world.While all changes from the technical to the emo-

tional product world, as indicated byarrows in Fig. 6,show the same direction in function 3, this is not thecase for function 2.The lowest panel in Fig. 6 depictsthat the group centroids of the untreated (control)hair sample and the silicate-shampoo-treated hairsample move in a positive hedonistic direction underthe setting of the emotional product world, while thestandard-shampoo-treated hair sample centroidmoves into the opposite direction.An explanation of this di¡erent in£uence of the

change in the product world on the hair samplesunder investigation can be facilitated by the resultsof the traditional sensoryassessment (Fig. 10), wherethe performance of the silicate shampoo-treated hairsample was rather similar to the untreated hair sam-ple, showing only minor advantages in luster, careand load after combing and some disadvantages likean enhanced harshness or a decreased stylability. Asawhole, these di¡erences are so subtle that they canonly be di¡erentiated by an expert panel ^ whichwas indeed our intention, as we wanted to knowwhether the physiological experiments yield a betterdi¡erentiation and if the small objective di¡erencescould be augmented by the‘product worlds’ like withamagnifying glass.The performance of the standardshampoo-treated sample, however, was more dis-tinct, showing prominent and favourable e¡ects likea better combability, increased softness and a plea-sant touch.A reasonable conclusion is that the better the

actual product performance can be detected by sub-jective methodology, the more convincing is itsembedding into a technically orientated productworld. However, the fewer subjectively perceptibledi¡erences between products appear, the more e¡ec-tive, respectively more necessary, will be the intro-duction of an emotional product world. Anadvantage of the emotional world can be also seenin the diagonal of Table IIIwhere the re-classi¢cationin this world is slightly better than in the technicalworld.The conclusion is that the arrangement of a suita-

ble product world is extremely important in case ofrather small subjectively perceptible di¡erencesbetween the products themselves. Because the tech-nical limits of the cosmetic products are attained in

most cases, associations and emotions that are con-nected to the products rather thantheirobjectiveper-formance will contribute to their di¡erentiation bythe consumer.The better the quality of cosmetic pro-ducts gets, themore it will be necessary to ‘emotiona-lize’them[see 8,19].The present study has revealed the possibility to

objectively assess the emotional properties of such‘emotionalized’cosmetic products by means of OEA,a multivariate psychophysiological technique, thesuperiority of which over a traditional sensoryassessment has also been demonstrated.Anotheraspect of product evaluationthat has tobe

taken into regard is the expertise of the subjects usedin the assessment procedure. Experts get moreexcited by certain product treatments in the techni-cal world which they are more familiar with thanwith the emotional world, which in turn exerts moreexcitement in the laymen (Fig.7). Laymen are moregenerally aroused as re£ected in the NS.SCR fre-quency (Fig.7), as they are unfamiliar with theexperimental laboratory situation, but experts get ingeneral more interested in the characteristics of theproducts, as shown by their increased PVA modula-tion (Fig. 8). However, laymen respond more posi-tively to the hair sample treatments, whereasexperts show no changes in zygomaticus activityacross the product samples (Fig. 9). Again, the psy-chophysiological approach of OEA allows for a ¢ne-grained analysis of e¡ects that are not re£ected insubjective ratings or in the traditional sensoryassessment.The psychophysiological gender e¡ects in the pre-

sent study were not very impressive. Apart from hav-ing a higher HR than males which is a general¢nding in psychophysiology, females responded tothe silicate-shampoo treatment with more intensecognitive processing as expressed by HRV. More pro-minent gender e¡ects, however, showed up in thesubjective domain, where males rated all three hairsamples as more‘voluminous’and females respondedmore favourable to the emotional world, rating allhair samples as more ‘pleasant’ than males, whereasthey rated them as more ‘dull’ in the technical world.Those gender-typical idiosyncrasiesmayappear dur-ing all kinds of product testing but especially in hairtreatments, where expectations of males and femalesmaydi¡er considerably.Although the present study constitutes a ¢rst

attempt to use multivariate statistical procedures forevaluating signi¢cant changes in psychophysiolog-ical responses to rather subtle di¡erences in product



properties, the methodology introduced here hassome promises for further investigations in thedomain of cosmetic product evaluation. Especially,the e¡ects of product ‘emotionalization’ by means ofintroducing an emotional world in connection withproducts that do not di¡er considerably in their sub-jectively detectable properties can be revealed suc-cessfully with the OEA methodology applied in thepresent study.

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Documents

Objective emotional assessment of tactile hair properties and their modulation by different product worlds