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A Comparative Study on Facially Expressed Emotions in Response to Basic Tastes Wender L. P. Bredie, Hui Shan Grace
Tan & Karin Wendin
Chemosensory Perception

ISSN 1936-5802
Chem. Percept.
DOI 10.1007/s12078-014-9163-6
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DOI 10.1007/s12078-014-9163-6 A Comparative Study on Facially Expressed Emotionsin Response to Basic Tastes Wender L. P. Bredie & Hui Shan Grace Tan &Karin Wendin Received: 17 May 2013 / Accepted: 12 January 2014 # European Union 2014 Abstract Facially expressed emotions play a role in commu- expressed emotions although it may not completely represent nication between individuals. They form another means of the dimensions of the emotional experience.
expressing oneself besides verbal expressions or self-reporting of feelings and perceptions on psychometric scales Keywords Sensory perception . Facial expression .
and are implicit in nature. This study aimed to evaluate the Emotion . Basic taste extent and specificity of evoking facial expressed emotions bybasic tastes and to evaluate if facially expressed emotionsprovide additional information to explicit measures. The emo- tions were characterised upon tasting the five basic tastes inaqueous solutions at three different concentrations levels. The Facial expressions are consciously or subconsciously con- sensory and emotional responses reported were obtained from veyed by an individual and are regarded to be a convenient a 21-membered taste panel. Facial reactions and facially way of identifying emotions (Russell and Dols ; Sicile- expressed emotions depended on the taste quality and taste Kira and Grandin The analysis of facial expressions intensity. However, the facially expressed emotions were gen- has been shown to be a reliable and non-obtrusive way of erally weak even for the relatively strong taste intensities.
accessing emotional information (Matsumoto et al. ; Bitter (caffeine), sour (citric acid) and salty (sodium chloride) Weiss et al. Ekman (, ) found a set of lead to clear disgust and surprise responses, whereas, sweet universal emotions, which were fundamentally and distin- (sucrose) and umami (glutamic acid monosodium salt) taste guishably different in their physiological and behavioural gave weakly noticeable facially expressed emotions.
characteristics. These so-called basic emotions were defined Although correlations between the expressed emotions and as ‘happiness', ‘sadness', ‘surprise', ‘disgust', ‘anger', ‘fear' hedonic responses were observed, the affective experience and ‘contempt'. There is much evidence that Ekman's basic had a limited predictive ability for the facially expressed emotions also elicit specific facial configurations.
emotion at the individual level. In conclusion, psychometric Identification of basic emotions from facially expressed emo- rating of the hedonic response is easier to assess than facially tions have been obtained reliably by trained or naïve persons,even with subjects from divergent cultures (Ekman andFriesen , ; Izard ; Matsumoto et al.
W. L. P. Bredie H. S. G. Tan K. WendinDepartment of Food Science, Faculty of Science, University of Basic tastes reveal specific facial reactions (Rosenstein and Copenhagen, Copenhagen, Denmark Oster Steiner Wendin et al. ). Studieswith infants determined that facial reactions to tastes were innate and remained more or less unchanged into adulthood SP Technical Research Institute of Sweden, IDEON, Lund 223 70,Sweden (Greimel et al. ; Steiner ). Specific basic tastes can elicit different facial reactions that can be related to basicemotions (Ekman Strong generally negative facial reactions have been reported to sour and bitter tastes, whereas Food and Meal Science, Kristianstad University, Kristianstad,Sweden weak responses have been observed for umami taste. The Author's personal copy Chem. Percept.
response to sweet taste has been reported to be positive but are realistic in foods. The overall aim of the study was to with a weak facially expressed emotions (Greimel et al. assess if facially expressed emotions for basic tastes would Zeinstra et al. ). Rosenberg ) showed that facial provide additional information to the explicit measure of reactions were independent of a person's cultural background.
liking. For this purpose, the seven basic emotions of Ekman The preference for sweetness and aversion to bitterness are also for all of the basic tastes were evaluated in a comparative independent of culture albeit more pronounced in childhood study design.
than in adulthood (Nicklaus et al. ; Reed et al. ).
Facial reactions in general are ways of communication in order to relay meaningful information between people Materials and Methods (Erickson and Schulkin ; Soussignan and Schaal ).
They serve a variety of functions in different social contexts, Sample Preparation for instance, negative expressions could simply serve as anindication of distaste or as a warning sign of potential danger Aqueous solutions of sucrose (Sigma-Aldrich, USA, purity (Rosenstein and Oster Rozin and Fallon whereas >99.5 %), sodium chloride (J.T. Baker, USA, purity >99 %), positive expressions could serve as a display of sensory plea- caffeine (Sigma-Aldrich, USA, purity >99 %), citric acid sure or positive reinforcement to encourage a caregiver monohydrate (Merck, Germany, purity >99.5 %) and glutamic (Erickson and Schulkin It is commonly accepted that acid monosodium salt monohydrate (Fluka, Switzerland, pu- emotional states of an individual influence food choices and rity >98 %) were each prepared in three concentrations. The intake (Macht ; Canetti et al. Ganley concentrations were chosen to be approximately iso-intense Robbins and Fray ).
and responded to weak, moderate and moderate-strong taste Even though facially expressed emotions to basic tastes intensities according to (ISO8586-1:ISO have been reported in different studies (Greimel et al. 3972)). The concentration levels of the tastant solu- Zeinstra et al. ), no systematic work has been done to tions are shown in Table . The water used was deionised and compare these emotions to basic tastes at different taste inten- filtered using MilliQ equipment (Merck Millipore, Germany).
sity levels that are commonly encountered in foods. Earlier The tastant solutions as well as purified water were served in work has often reported on relatively high taste stimulation in 30-ml aliquots in plastic transparent cups at room temperature.
order to identify the most characteristic emotions. Althoughthese studies have linked basic emotions to basic tastes, it israther unclear as to which importance should be given to the Subjects and Sample Evaluation facially expressed emotion in comparison weaker taste per-ceptions. Furthermore, the relationship between the hedonic Twenty-one adults (11 females and 10 males; non-smokers; experience for different strengths of basic tastes and the se- aged 19 to 62, mean 29.4 years) were selected on their general verity of the facially expressed emotion is not well sensory abilities according to ISO recommendations (ISO established. With the increasing interest for implicit measures Prior to the taste study, the subjects were of sensory perception, it is of interest to investigate, if facially informed about the study objectives and signed a consent form expressed emotions may provide additional information to where they agreed to the video recording and handling of the explicit measures, especially in the range of stimulus intensi- data. All subjects could correctly identify the basic tastes and ties with relevance to foods.
could distinguish the perceived intensity between the three In a recent study, basic tastes at varying intensity levels were reported to elicit different facial reactions, which were The subjects were included in a taste panel and were dependent on the quality and intensity of the taste stimuli instructed to take a sip from the taste solution, form an opinion (Wendin et al. ). The taste intensity clearly influenced about the sample and spit out the solution. Subsequently, they facial reactions to basic tastes, with movements of the lips(sourness) and the responses of the eyes and forehead Table 1 Concentrations of the solutions tasted by the sensory panel with (bitterness) as most pronounced effects. In the present study, their taste characteristic given in the parenthesis the data from Wendin et al. () were further analysed by a Low (g/L) Medium (g/L) High (g/L) panel trained on Ekman's basic emotions in order to investi-gate the relations between taste stimulation, the hedonic re- sponse and facially recognisable emotions. The degree of Sodium chloride (salty) facially expressed emotions was measured as a function of Caffeine (bitter) the intensity of each of the five basic taste qualities. The Citric acid monohydrate (sour) 0.60 objectives were to characterise the facially expressed emo- Sodium glutamate (umami) tions in relation to basic taste perception at intensity levels that Author's personal copy Chem. Percept.
evaluated the degree of liking or disliking of the sample on the over a 6-week period. In order to eliminate systematic nine-point hedonic scale (Jones et al. identified the contrast effects, the order of the evaluations was ran- taste, and scored the taste intensity on a nine-point intensity domized within each rating panel member. The emotion scale. A short pause between each tasting was allowed to let rating panel members assessed the videos without any the subject recover to base-line. Each subject participated in information about the test samples. After the rating three replicate sessions, in which all 16 samples were tasted in panellists completed their assignment, they were asked a randomized order. The subjects performed the evaluations to re-evaluate two selected videos twice in order to alone in a neutral room, which was free from odours and assess the panel member repeatability in performing visual distractions. During the session, the subject was stand- facial readings.
ing behind a fixed rostrum. When sipping a sample the subjectwas asked to look at a fixed position on the wall in front. Eachtasting session lasted approximately 20 min. All subjects in the taste panel received a token for their participation in thethree tasting sessions (Wendin et al. ).
Reliability of the Emotion Rating Panel Facial Recordings The reliability of the emotion rating panel was assessed interms of their consensus and repeatability. The consensus During the tasting of a sample, the face of the subject was between the rating panel members was evaluated by a recorded using a 360° dome camera (Panasonic System, Tucker 1 analysis. For all the significant basic emotions, a USA) with a 22× optical zoom. The digital camera was high panel consensus was observed. The repeatability of the mounted on the ceiling approximately 3 m from the subject.
individual rating panel members were assessed from one-way The camera was remote-controlled from an adjacent controller ANOVAs with taste samples as a factor (p×MSE plots). The room, where an operator managed the recordings on a PC in a emotion rating panel members showed a general good repeat- MPEG4 file format.
ability. The rating panel performance analyses were executedin PanelCheck v1.3.2 (Nofima, Ås, Norway).
Emotions Rating Panel Six volunteers from the University of Copenhagen, Faculty of Analysis of Hedonic Scores and Facially Expressed Emotions Science, were recruited for the emotion rating panel. The for the Basic Tastes panel was trained to reliably recognise and scale the intensityof the facially expressed seven basic emotions ‘happiness', The emotion scores were analysed by a full two-way ANOVA ‘sadness', ‘surprise', ‘anger', ‘disgust', ‘contempt' and ‘fear' for all the samples and sensory taste subjects. A subsequent according to Ekman , ). During the training, Tukey's HSD test was used to show the significant differences the emotion raters panel were provided with definitions of the between the samples. The hedonic scores from the sensory basic emotions and were shown pictures as well as videos that taste panel for the basic taste solutions and the purified water displayed the typical facial features (Fig. At the end of the were analysed by a three-way ANOVA with the samples and training sessions, the emotion raters panel agreed on how to replicate as fixed effect and the taste subjects as random effect quantitatively rate the basic emotions in the recordings.
including all two-way interaction terms. Tukey's HSD test The basic emotions expressed by the face were measured was performed to show the significant differences between on a four-point category scale including the categories: not at the samples. All ANOVAs were run in IBM SPSS Statistics, v all (0), a little (1), moderate (4) and a lot (8). The scale values 20.0.0 (IBM Corp., USA).
given in the parenthesis were used in the data analysis. Thescale was a simplified version of the original multi-scalarrating scale (Matsumoto et al. ). For the purpose of this Correlation Analysis of Facially Expressed Emotions Towards study, the nine-point multi-scalar scale was deemed to be too Hedonics and FACS detailed, since many of the facially expressed emotions ap-peared to be at the low-end of the intensity scale.
Pearson correlation coefficients between pleasantness A total of 63 MPEG4 recordings were analysed by and intensity of facially expressed emotions were calcu- the emotion rating panel. The recordings consisted of lated as well as correlation coefficients between facially the three replicates of 21 subjects from the taste panel expressed emotions and facial reactions (FACS) by the tasting 16 samples (3 concentrations × 5 basic tastes and use of IBM SPSS Statistics, v 20.0.0 (IBM corp., USA).
demineralised water (Millipore (Merck, Germany))). The In both cases, the data were averaged over the sensory rating panellists each evaluated all of the recordings taste replicates.

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Fig. 1 Typical facial expressions used in the training of the panel to rate the basic emotions Facially Expressed Emotions to Basic Tastes Hedonic Responses to Basic Tastes The facially expressed emotions at the sensory taste panellevel were observed to be more pronounced with increasing The sensory taste panel rated their degree of liking or concentrations of the taste solutions (Fig. ‘Disgust' and to a disliking of the basic taste solutions and water in three lesser extent ‘surprise' were the most evident facial expressed replicates. The hedonic ratings for the basic tastes var- emotions. However, the observed strength of these emotions ied between the sensory taste subjects, however, they were between "a little" and "moderate" on the rating scale.
made consistent judgements since the replicate effect The facially expressed emotions for the basic tastes as com- (p< 0.05) for the hedonic scores was not significant in pared to the response to water are shown in Table The the ANOVA. In order to compare the hedonic responses negative emotion disgust was most marked for bitter, salty for the different taste solutions, the taste panel × repli-cate-averaged hedonic ratings were calculated. The datashowed the highest hedonic scores for water and thesucrose solutions (Fig. ). The hedonic scores for su-crose (sweet) and glutamic acid monosodium salt(umami) solutions did not significantly (p< 0.05) changewith increasing concentration. However, increasing theconcentration of sodium chloride (salty), caffeine (bitter)and citric acid (sour) significantly (p< 0.05) lowered thehedonic ratings. The sweet solutions and water wereperceived from ‘neutral' to ‘like moderately', whereasumami was perceived from ‘neutral' to ‘dislike moder-ately' by the panel. The salty, bitter and sour tasteswere perceived from ‘neutral' to ‘dislike moderately'.
At the highest concentration, these latter tastants wereperceived from ‘dislike moderately' to ‘dislike strongly'.
The bitter, salty, sour and umami taste solutions were,therefore, mainly representative for a negative hedonic Fig. 2 Hedonic scores (sensory panel mean) for the different taste and response. The sweet taste solutions and water represent- water solutions. Bars with entirely different superscript letters show ed mostly a weak positive hedonic response.
significant (p<0.05) hedonic difference

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(a) Sweet Taste
Table 2 Facially expressed basic emotions evoked by the different levels of taste stimulation in comparison to water Facially expressed emotionsa Moderate to strong (b) Salty Taste
Anger (*), disgust (***), Moderate to strong Anger (***), contempt (**), Moderate to strong Anger (***), contempt (*), disgust (***), surprise (***) (c) Bitter Taste
Disgust (***), surprise (**) Moderate to strong Disgust (***), surprise (***) Moderate to strong a Significantly (*p<0.05; **p<0.01; ***p<0.001) higher when comparedwith the facial emotions evoked from water alone (d) Sour Taste
Relationships Between Basic Emotions and Hedonic Pearson correlations between the hedonic response and the (e) Umami Taste
facially expressed emotion were calculated for the combined data for all of the taste solutions. The correlations between the hedonic responses and the facially expressed emotions were generally low but significant (p<0.05) for the emotions sur- prise, contempt, disgust, anger and sadness (Fig. ). In all of these cases the correlation coefficients were negative, indi-cating that the severity of the facial emotion decreasedwith a higher positive hedonic response. The correla- Fig. 3 The mean emotion scores for the taste panel facial responses to the tions for the facial emotions of fear (r= −0.098) and taste and water solutions. The graphs represent the responses for ‘sweet- happiness (r= 0.053) were not significant (Fig. ).
ness' (a), ‘salty' (b), ‘bitter' (c), ‘sour' (d), and ‘umami' (e), respectively.
The emotion scale varied from 0 (not at all), 1 (a little), 4 (moderate) to 8 Individual differences between the hedonic responses and the facially expressed emotions were mainly ob-served for disgust but also for surprise, contempt andanger. In cases where a basic taste was perceived as and sour tastes and showed significant (p<0.05) increases for disliked, the variation in the facial expressions was most the medium and high concentrations used. Even though the evident. At the individual level, some sensory subjects expressed emotions were generally weak, the expression in the taste panel could express the emotions disgust of surprise significantly increased with increasing con- and surprise to a greater extent, as indicated by "mod- centrations for bitter, salty, sour and sweet taste. The erate" to "a lot" by the emotion rating panel. The salty and bitter tastes also revealed weak facial greatest scores for surprise were obtained when the taste expressed emotions of anger and contempt, albeit sig- was disliked. Samples with the lowest surprise scores nificant only for the highest concentration.
were those that were liked most. Other stimuli than Author's personal copy Chem. Percept.
could be explained by the generally low scores for Emotions expressed facially have been quantified in relation to basic taste perception under controlled and comparative conditions. Although the information of being recorded may have influenced the expressiveness of the facial reactions, the taste subjects had consistent facial reactions over the An emotion rating panel was used for the identification and scaling of the vigorousness and specificity of the facially expressed emotions. A good agreement and consistent judg- ment between the rating panel members was obtained, which was in agreement with other studies using such methodology.
Instructed naïve observers from various cultural origins have indeed been shown to give reliable interpretations of the facially expressed basic emotions (Ekman and Friesen ; Matsumoto et al. ).
The facially expressed emotions were correlated to the particular facial reactions such as ‘frown', ‘eye widening', Fig. 4 Relationships between the hedonic response and the facially ‘eye diminishing', ‘nose wrinkle' and ‘nostril widening'.
expressed basic emotions. Data points represent the replicate-averageddata for the individual sensory subjects However, the typical expressions around the mouth and lipsassociated with the basic emotions of happiness, surprise,sadness, fear and disgust were less clearly correlated to thefacially observed reactions. This may be explained by the basic tastes alone may be needed to create a surprise generally low expression of these emotions in relation to basic reaction with a positive hedonic response.
tastes. In earlier work (Wendin et al. the intensity ofmost facial reactions to basic tastes increased with increasing Relationships Between Basic Emotions and Facial Reactions stimulus concentration, most pronounced for sourness (lips)and bitterness (eyes and forehead). In comparison to the The Pearson correlations between the facial reactions as scoring of a multitude of facial reactions, which are difficult measured by FACS (Wendin et al. ) and the facial- to interpret in terms of emotional content, the Ekman scheme ly expressed emotions were calculated. The correlations of seven basic emotions proved to be less informative due were generally high for the emotions anger, disgust and weak responses for few emotions.
contempt and surprise (Table ). The facial emotions Facially expressed emotions for basic tastes have been anger, disgust and contempt all had significant positive reported in other studies (Greimel et al. Nicklaus et al.
correlation coefficients varying between 0.83 and 0.99 Rosenstein and Oster ; Rozin et al. ; with the facial reactions of ‘frown', ‘eye diminishing' Scinska-Bienkowska et al. ; Steiner Steiner et al.
and ‘nose wrinkle'. The facial expressed emotion sur- ). However, the present study evaluated the facially prise had a significant correlation coefficient of 0.97 expressed emotions evoked by the basic tastes at different with the facial reaction ‘eye widening'. The facial ex- sensory intensities in a comparative manner. The observations pression ‘lip corner down' had the highest significant of this study were in general agreement with previous work on correlation (0.77) for disgust. Whereas ‘lips pursed' and facial reactions as responses to basic tastes. The unpleasant ‘mouth open' were correlated significantly with surprise stimuli such as bitter taste or high intensities of salty or sour with coefficients of 0.76 and 0.73, respectively. These tastes evoked stronger facially expressed emotions than pleas- facial reactions fitted well with the expressed emotions ant and neutral stimuli such as sweet and umami tastes (Hu (Fig. ). Other features measured by FACS had lower et al. ; Rozin ; Steiner Zeinstra et al. correlation coefficients with the facially expressed emo- Among the different taste responses in this study, it was tions. The facial reaction of ‘lips corner up' had low evident that disgust received the highest ratings. Disgust has correlations to the facially expressed emotions, which indeed been considered as an emotion with a strong and Author's personal copy Chem. Percept.
Table 3 Pearson's correlations ofthe observed basic emotions and Facially expressed emotion the facial reactions (FACS) foundin the previous study by Wendin et al. (), values in italics in-dicate significance, p≤0.05 characteristic facial expression (Rozin and Fallon communicated facially by individuals. Other forms like verbal Greimel et al. There is support from other studies that expressions or other kinds of gestures may be more important negative responses to disliked tastes are expressed more in conveying information about distaste. The absence of a strongly than positive responses towards liked tastes (Horio facially expressed emotion is not necessarily a predictor for Negative taste responses are expressed more instanta- the absence emotions, but could be due to a lack of reason to neously and unambiguously (Greimel et al. Steiner express, due to masking and control (Zeinstra et al. ) or and are less influenced by the existing emotional state due to the emotional process itself not eliciting sufficient facial (Greimel et al. They are thus often deemed easier to activity to be interpretable to the observer (Tassinary and distinguish and identify than positive responses to taste.
Cacioppo Therefore, it is suggested that measurement Higher concentrations of the taste solutions evoked greater of the affective response for taste could include a wider intensities of facially expressed emotions. The emotions were spectrum of observational and other methods than only the not consistent across the basic tastes, e.g. the emotion surprise facially expressed emotions.
was clearly observed for high concentrations of sour and bitter A taste or a flavour in food may also elicit a sequence of solutions. While these were not the case for sweet, umami and sensory experiences due to temporal changes in intensity salty samples. Earlier studies have not taken into account the which may interact with emotions during tasting. For instance, variation of perceived intensity of taste solutions in relation to a reaction to a bitter stimulus could include surprise, followed different psychophysical functions of stimulus (Stevens by disgust and perhaps further by anger and contempt. This is Janestad et al. Wendin et al. However, from the in line with Lewis ), who concluded that emotions can results it is obvious that the intensity and type of emotions have anticipative, immediate and cognitive aspects. Clearly, elicited relate to the perceived intensity of the taste stimuli.
some emotions seem to be related to the anticipation of the Nevertheless, the vigorousness of the facial expressed emo- stimulus (e.g. surprise), whereas others seem to be driven by tion remained generally low, even at the highest taste the sensory experience itself and the subsequent cognitive processing of the stimulus. More detailed studies are sug- It was observed that the range of basic tastes in the present gested to further address such dynamic features of taste and study was rated relatively low on the degree of liking. Foods flavour responses. The interactions with emotions evoked by can be expected to evoke greater positive affective responses.
the specific context and environment could also be further Therefore, they may give more distinct facially expressed emotions. Further studies with real foods may be consideredto confirm if the facial emotions could reveal moreinformation.
It was interesting to note that the greatest individual vari- ation in facially expressed emotions was expressed for the The perception of basic tastes revealed facial reactions and tastes that were rated as disliked. However, even if a taste was facially expressed emotions, which were dependent on the disliked, the expected negative facial emotion was not neces- kind of taste quality. For most basic tastes, the severity of sarily expressed equally strong at the individual level. This the facial expressed emotions increased with the intensity of would suggest that a negative affect for a taste is not always the taste stimulus. Facially expressed emotions caused by Author's personal copy Chem. Percept.
basic tastes were generally weak. Bitter, sour and salty gave ISO 3972. (3972:1991(E)). Sensory analysis—methodology—method of clear disgust and surprise responses, whereas, sweet and uma- investigating sensitivity of taste. International Organisation forStandardization, Geneva, Switzerland.
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