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
1 23
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Chem. Percept.
DOI 10.1007/s12078-014-9163-6
A Comparative Study on Facially Expressed Emotions
in 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 communication between individuals. They form another means of
expressing oneself besides verbal expressions or selfreporting of feelings and perceptions on psychometric scales
and are implicit in nature. This study aimed to evaluate the
extent and specificity of evoking facial expressed emotions by
basic tastes and to evaluate if facially expressed emotions
provide additional information to explicit measures. The emotions were characterised upon tasting the five basic tastes in
aqueous solutions at three different concentrations levels. The
sensory and emotional responses reported were obtained from
a 21-membered taste panel. Facial reactions and facially
expressed emotions depended on the taste quality and taste
intensity. However, the facially expressed emotions were generally weak even for the relatively strong taste intensities.
Bitter (caffeine), sour (citric acid) and salty (sodium chloride)
lead to clear disgust and surprise responses, whereas, sweet
(sucrose) and umami (glutamic acid monosodium salt) taste
gave weakly noticeable facially expressed emotions.
Although correlations between the expressed emotions and
hedonic responses were observed, the affective experience
had a limited predictive ability for the facially expressed
emotion at the individual level. In conclusion, psychometric
rating of the hedonic response is easier to assess than facially
W. L. P. Bredie : H. S. G. Tan : K. Wendin
Department of Food Science, Faculty of Science, University of
Copenhagen, Copenhagen, Denmark
K. Wendin (*)
SP Technical Research Institute of Sweden, IDEON, Lund 223 70,
Sweden
e-mail: [email protected]
K. Wendin
Food and Meal Science, Kristianstad University, Kristianstad,
Sweden
expressed emotions although it may not completely represent
the dimensions of the emotional experience.
Keywords Sensory perception . Facial expression .
Emotion . Basic taste
Introduction
Facial expressions are consciously or subconsciously conveyed by an individual and are regarded to be a convenient
way of identifying emotions (Russell and Dols 1998; SicileKira and Grandin 2006). The analysis of facial expressions
has been shown to be a reliable and non-obtrusive way of
accessing emotional information (Matsumoto et al. 2000;
Weiss et al. 1999). Ekman (1993, 1999, 2003) found a set of
universal emotions, which were fundamentally and distinguishably different in their physiological and behavioural
characteristics. These so-called basic emotions were defined
as ‘happiness’, ‘sadness’, ‘surprise’, ‘disgust’, ‘anger’, ‘fear’
and ‘contempt’. There is much evidence that Ekman’s basic
emotions also elicit specific facial configurations.
Identification of basic emotions from facially expressed emotions have been obtained reliably by trained or naïve persons,
even with subjects from divergent cultures (Ekman and
Friesen 1971, 1978, 1986; Izard 1971; Matsumoto et al.
2000; Weiss et al. 1999).
Basic tastes reveal specific facial reactions (Rosenstein and
Oster 1988, 1997; Steiner 1979; Wendin et al. 2011). Studies
with infants determined that facial reactions to tastes were
innate and remained more or less unchanged into adulthood
(Greimel et al. 2006; Steiner 1979). Specific basic tastes can
elicit different facial reactions that can be related to basic
emotions (Ekman 2003). Strong generally negative facial
reactions have been reported to sour and bitter tastes, whereas
weak responses have been observed for umami taste. The
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response to sweet taste has been reported to be positive but
with a weak facially expressed emotions (Greimel et al. 2006;
Zeinstra et al. 2009). Rosenberg (1997) showed that facial
reactions were independent of a person’s cultural background.
The preference for sweetness and aversion to bitterness are also
independent of culture albeit more pronounced in childhood
than in adulthood (Nicklaus et al. 2005; Reed et al. 2006).
Facial reactions in general are ways of communication in
order to relay meaningful information between people
(Erickson and Schulkin 2003; Soussignan and Schaal 1996).
They serve a variety of functions in different social contexts,
for instance, negative expressions could simply serve as an
indication of distaste or as a warning sign of potential danger
(Rosenstein and Oster 1988; Rozin and Fallon 1987), whereas
positive expressions could serve as a display of sensory pleasure or positive reinforcement to encourage a caregiver
(Erickson and Schulkin 2003). It is commonly accepted that
emotional states of an individual influence food choices and
intake (Macht 1999, 2008; Canetti et al. 2002; Ganley 1989;
Robbins and Fray 1980).
Even though facially expressed emotions to basic tastes
have been reported in different studies (Greimel et al. 2006;
Zeinstra et al. 2009), no systematic work has been done to
compare these emotions to basic tastes at different taste intensity levels that are commonly encountered in foods. Earlier
work has often reported on relatively high taste stimulation in
order to identify the most characteristic emotions. Although
these studies have linked basic emotions to basic tastes, it is
rather unclear as to which importance should be given to the
facially expressed emotion in comparison weaker taste perceptions. Furthermore, the relationship between the hedonic
experience for different strengths of basic tastes and the severity of the facially expressed emotion is not well
established. With the increasing interest for implicit measures
of sensory perception, it is of interest to investigate, if facially
expressed emotions may provide additional information to
explicit measures, especially in the range of stimulus intensities with relevance to foods.
In a recent study, basic tastes at varying intensity levels
were reported to elicit different facial reactions, which were
dependent on the quality and intensity of the taste stimuli
(Wendin et al. 2011). The taste intensity clearly influenced
facial reactions to basic tastes, with movements of the lips
(sourness) and the responses of the eyes and forehead
(bitterness) as most pronounced effects. In the present study,
the data from Wendin et al. (2011) were further analysed by a
panel trained on Ekman’s basic emotions in order to investigate the relations between taste stimulation, the hedonic response and facially recognisable emotions. The degree of
facially expressed emotions was measured as a function of
the intensity of each of the five basic taste qualities. The
objectives were to characterise the facially expressed emotions in relation to basic taste perception at intensity levels that
are realistic in foods. The overall aim of the study was to
assess if facially expressed emotions for basic tastes would
provide additional information to the explicit measure of
liking. For this purpose, the seven basic emotions of Ekman
for all of the basic tastes were evaluated in a comparative
study design.
Materials and Methods
Sample Preparation
Aqueous solutions of sucrose (Sigma-Aldrich, USA, purity
>99.5 %), sodium chloride (J.T. Baker, USA, purity >99 %),
caffeine (Sigma-Aldrich, USA, purity >99 %), citric acid
monohydrate (Merck, Germany, purity >99.5 %) and glutamic
acid monosodium salt monohydrate (Fluka, Switzerland, purity >98 %) were each prepared in three concentrations. The
concentrations were chosen to be approximately iso-intense
and responded to weak, moderate and moderate-strong taste
intensities according to (ISO8586-1:1993(E); ISO
3972:1991(E)). The concentration levels of the tastant solutions are shown in Table 1. The water used was deionised and
filtered using MilliQ equipment (Merck Millipore, Germany).
The tastant solutions as well as purified water were served in
30-ml aliquots in plastic transparent cups at room temperature.
Subjects and Sample Evaluation
Twenty-one adults (11 females and 10 males; non-smokers;
aged 19 to 62, mean 29.4 years) were selected on their general
sensory abilities according to ISO recommendations (ISO
3972:1991(E)). Prior to the taste study, the subjects were
informed about the study objectives and signed a consent form
where they agreed to the video recording and handling of the
data. All subjects could correctly identify the basic tastes and
could distinguish the perceived intensity between the three
concentration levels.
The subjects were included in a taste panel and were
instructed to take a sip from the taste solution, form an opinion
about the sample and spit out the solution. Subsequently, they
Table 1 Concentrations of the solutions tasted by the sensory panel with
their taste characteristic given in the parenthesis
Compound
Low (g/L) Medium (g/L) High (g/L)
Sucrose (sweet)
Sodium chloride (salty)
Caffeine (bitter)
Citric acid monohydrate (sour)
Sodium glutamate (umami)
12.00
2.00
0.27
0.60
1.00
24.00
4.00
0.54
1.20
2.00
48.00
8.00
1.08
2.40
4.00
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evaluated the degree of liking or disliking of the sample on the
nine-point hedonic scale (Jones et al. 1955), identified the
taste, and scored the taste intensity on a nine-point intensity
scale. A short pause between each tasting was allowed to let
the subject recover to base-line. Each subject participated in
three replicate sessions, in which all 16 samples were tasted in
a randomized order. The subjects performed the evaluations
alone in a neutral room, which was free from odours and
visual distractions. During the session, the subject was standing behind a fixed rostrum. When sipping a sample the subject
was asked to look at a fixed position on the wall in front. Each
tasting session lasted approximately 20 min. All subjects in
the taste panel received a token for their participation in the
three tasting sessions (Wendin et al. 2011).
over a 6-week period. In order to eliminate systematic
contrast effects, the order of the evaluations was randomized within each rating panel member. The emotion
rating panel members assessed the videos without any
information about the test samples. After the rating
panellists completed their assignment, they were asked
to re-evaluate two selected videos twice in order to
assess the panel member repeatability in performing
facial readings.
Facial Recordings
The reliability of the emotion rating panel was assessed in
terms of their consensus and repeatability. The consensus
between the rating panel members was evaluated by a
Tucker 1 analysis. For all the significant basic emotions, a
high panel consensus was observed. The repeatability of the
individual rating panel members were assessed from one-way
ANOVAs with taste samples as a factor (p×MSE plots). The
emotion rating panel members showed a general good repeatability. The rating panel performance analyses were executed
in PanelCheck v1.3.2 (Nofima, Ås, Norway).
During the tasting of a sample, the face of the subject was
recorded using a 360° dome camera (Panasonic System,
USA) with a 22× optical zoom. The digital camera was
mounted on the ceiling approximately 3 m from the subject.
The camera was remote-controlled from an adjacent controller
room, where an operator managed the recordings on a PC in a
MPEG4 file format.
Data Analysis
Reliability of the Emotion Rating Panel
Emotions Rating Panel
Six volunteers from the University of Copenhagen, Faculty of
Science, were recruited for the emotion rating panel. The
panel was trained to reliably recognise and scale the intensity
of the facially expressed seven basic emotions ‘happiness’,
‘sadness’, ‘surprise’, ‘anger’, ‘disgust’, ‘contempt’ and ‘fear’
according to Ekman (1993, 1999, 2003). During the training,
the emotion raters panel were provided with definitions of the
basic emotions and were shown pictures as well as videos that
displayed the typical facial features (Fig. 1). At the end of the
training sessions, the emotion raters panel agreed on how to
quantitatively rate the basic emotions in the recordings.
The basic emotions expressed by the face were measured
on a four-point category scale including the categories: not at
all (0), a little (1), moderate (4) and a lot (8). The scale values
given in the parenthesis were used in the data analysis. The
scale was a simplified version of the original multi-scalar
rating scale (Matsumoto et al. 2000). For the purpose of this
study, the nine-point multi-scalar scale was deemed to be too
detailed, since many of the facially expressed emotions appeared to be at the low-end of the intensity scale.
A total of 63 MPEG4 recordings were analysed by
the emotion rating panel. The recordings consisted of
the three replicates of 21 subjects from the taste panel
tasting 16 samples (3 concentrations×5 basic tastes and
demineralised water (Millipore (Merck, Germany))). The
rating panellists each evaluated all of the recordings
Analysis of Hedonic Scores and Facially Expressed Emotions
for the Basic Tastes
The emotion scores were analysed by a full two-way ANOVA
for all the samples and sensory taste subjects. A subsequent
Tukey’s HSD test was used to show the significant differences
between the samples. The hedonic scores from the sensory
taste panel for the basic taste solutions and the purified water
were analysed by a three-way ANOVA with the samples and
replicate as fixed effect and the taste subjects as random effect
including all two-way interaction terms. Tukey’s HSD test
was performed to show the significant differences between
the samples. All ANOVAs were run in IBM SPSS Statistics, v
20.0.0 (IBM Corp., USA).
Correlation Analysis of Facially Expressed Emotions Towards
Hedonics and FACS
Pearson correlation coefficients between pleasantness
and intensity of facially expressed emotions were calculated as well as correlation coefficients between facially
expressed emotions and facial reactions (FACS) by the
use of IBM SPSS Statistics, v 20.0.0 (IBM corp., USA).
In both cases, the data were averaged over the sensory
taste replicates.
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Neutral
Anger
Happiness
Surprise
Sadness
Fear
Disgust
Contempt
Fig. 1 Typical facial expressions used in the training of the panel to rate the basic emotions
Results
Facially Expressed Emotions to Basic Tastes
Hedonic Responses to Basic Tastes
The facially expressed emotions at the sensory taste panel
level were observed to be more pronounced with increasing
concentrations of the taste solutions (Fig. 3). ‘Disgust’ and to a
lesser extent ‘surprise’ were the most evident facial expressed
emotions. However, the observed strength of these emotions
were between “a little” and “moderate” on the rating scale.
The facially expressed emotions for the basic tastes as compared to the response to water are shown in Table 2. The
negative emotion disgust was most marked for bitter, salty
The sensory taste panel rated their degree of liking or
disliking of the basic taste solutions and water in three
replicates. The hedonic ratings for the basic tastes varied between the sensory taste subjects, however, they
made consistent judgements since the replicate effect
(p<0.05) for the hedonic scores was not significant in
the ANOVA. In order to compare the hedonic responses
for the different taste solutions, the taste panel ×replicate-averaged hedonic ratings were calculated. The data
showed the highest hedonic scores for water and the
sucrose solutions (Fig. 2). The hedonic scores for sucrose (sweet) and glutamic acid monosodium salt
(umami) solutions did not significantly (p<0.05) change
with increasing concentration. However, increasing the
concentration of sodium chloride (salty), caffeine (bitter)
and citric acid (sour) significantly (p<0.05) lowered the
hedonic ratings. The sweet solutions and water were
perceived from ‘neutral’ to ‘like moderately’, whereas
umami was perceived from ‘neutral’ to ‘dislike moderately’ by the panel. The salty, bitter and sour tastes
were perceived from ‘neutral’ to ‘dislike moderately’.
At the highest concentration, these latter tastants were
perceived from ‘dislike moderately’ to ‘dislike strongly’.
The bitter, salty, sour and umami taste solutions were,
therefore, mainly representative for a negative hedonic
response. The sweet taste solutions and water represented mostly a weak positive hedonic response.
Fig. 2 Hedonic scores (sensory panel mean) for the different taste and
water solutions. Bars with entirely different superscript letters show
significant (p<0.05) hedonic difference
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(a) Sweet Taste
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Table 2 Facially expressed basic emotions evoked by the different levels
of taste stimulation in comparison to water
SweetLow
Taste intensity
Facially expressed emotionsa
Weak
Weak to moderate
Moderate to strong
Weak
None
None
Surprise (**)
None
Weak to moderate
Anger (*), disgust (***),
surprise (*)
Anger (***), contempt (**),
disgust (***)
Disgust (*)
Disgust (***)
Anger (***), contempt (*),
disgust (***), surprise (***)
None
Disgust (***), surprise (**)
Disgust (***), surprise (***)
None
Disgust (*)
Disgust (**)
SweetMed
SweetHigh
Sweetness
Water
Salty
(b) Salty Taste
3.0
2.5
2.0
1.5
1.0
0.5
0.0
SaltyLow
Moderate to strong
SaltyMed
SaltyHigh
Bitter
Weak
Weak to moderate
Moderate to strong
Sour
Weak
Weak to moderate
Moderate to strong
Weak
Weak to moderate
Moderate to strong
Water
(c) Bitter Taste
3.0
2.5
2.0
BitterLow
1.5
1.0
BitterMed
0.5
BitterHigh
0.0
Water
Umami
a
Significantly (*p<0.05; **p<0.01; ***p<0.001) higher when compared
with the facial emotions evoked from water alone
(d) Sour Taste
3.0
2.5
2.0
1.5
1.0
0.5
0.0
SourLow
SourMed
SourHigh
Water
(e) Umami Taste
3.0
2.5
2.0
1.5
UmamiLow
1.0
UmamiMed
0.5
UmamiHigh
0.0
Water
Fig. 3 The mean emotion scores for the taste panel facial responses to the
taste and water solutions. The graphs represent the responses for ‘sweetness’ (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
(a lot)
and sour tastes and showed significant (p<0.05) increases for
the medium and high concentrations used. Even though the
expressed emotions were generally weak, the expression
of surprise significantly increased with increasing concentrations for bitter, salty, sour and sweet taste. The
salty and bitter tastes also revealed weak facial
expressed emotions of anger and contempt, albeit significant only for the highest concentration.
Relationships Between Basic Emotions and Hedonic
Response
Pearson correlations between the hedonic response and the
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 surprise, contempt, disgust, anger and sadness (Fig. 4). In all of
these cases the correlation coefficients were negative, indicating that the severity of the facial emotion decreased
with a higher positive hedonic response. The correlations for the facial emotions of fear (r= −0.098) and
happiness (r= 0.053) were not significant (Fig. 4).
Individual differences between the hedonic responses
and the facially expressed emotions were mainly observed for disgust but also for surprise, contempt and
anger. In cases where a basic taste was perceived as
disliked, the variation in the facial expressions was most
evident. At the individual level, some sensory subjects
in the taste panel could express the emotions disgust
and surprise to a greater extent, as indicated by “moderate” to “a lot” by the emotion rating panel. The
greatest scores for surprise were obtained when the taste
was disliked. Samples with the lowest surprise scores
were those that were liked most. Other stimuli than
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8
6
4
2
0
8
6
4
2
0
8
6
4
2
0
8
6
4
2
0
8
6
4
2
0
8
6
4
2
0
8
6
4
2
0
r=-0.098
Fear
r=-0.201
Surprise
could be explained by the generally low scores for
happiness.
Discussion
1
2
3
r=-0.292
Contempt
r=-0.325
Disgust
r=-0.247
Anger
r=-0.110
Sadness
r=0.053
Happiness
4
5
6
7
8
9
Pleasantness
Fig. 4 Relationships between the hedonic response and the facially
expressed basic emotions. Data points represent the replicate-averaged
data for the individual sensory subjects
basic tastes alone may be needed to create a surprise
reaction with a positive hedonic response.
Relationships Between Basic Emotions and Facial Reactions
The Pearson correlations between the facial reactions as
measured by FACS (Wendin et al. 2011) and the facially expressed emotions were calculated. The correlations
were generally high for the emotions anger, disgust and
contempt and surprise (Table 3). The facial emotions
anger, disgust and contempt all had significant positive
correlation coefficients varying between 0.83 and 0.99
with the facial reactions of ‘frown’, ‘eye diminishing’
and ‘nose wrinkle’. The facial expressed emotion surprise had a significant correlation coefficient of 0.97
with the facial reaction ‘eye widening’. The facial expression ‘lip corner down’ had the highest significant
correlation (0.77) for disgust. Whereas ‘lips pursed’ and
‘mouth open’ were correlated significantly with surprise
with coefficients of 0.76 and 0.73, respectively. These
facial reactions fitted well with the expressed emotions
(Fig. 1). Other features measured by FACS had lower
correlation coefficients with the facially expressed emotions. The facial reaction of ‘lips corner up’ had low
correlations to the facially expressed emotions, which
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
repetitions.
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 judgment 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 1971;
Matsumoto et al. 2000).
The facially expressed emotions were correlated to the
particular facial reactions such as ‘frown’, ‘eye widening’,
‘eye diminishing’, ‘nose wrinkle’ and ‘nostril widening’.
However, the typical expressions around the mouth and lips
associated with the basic emotions of happiness, surprise,
sadness, fear and disgust were less clearly correlated to the
facially observed reactions. This may be explained by the
generally low expression of these emotions in relation to basic
tastes. In earlier work (Wendin et al. 2011), the intensity of
most facial reactions to basic tastes increased with increasing
stimulus concentration, most pronounced for sourness (lips)
and bitterness (eyes and forehead). In comparison to the
scoring of a multitude of facial reactions, which are difficult
to interpret in terms of emotional content, the Ekman scheme
of seven basic emotions proved to be less informative due
weak responses for few emotions.
Facially expressed emotions for basic tastes have been
reported in other studies (Greimel et al. 2006; Nicklaus et al.
2005; Rosenstein and Oster 1988, 1997; Rozin et al. 1994;
Scinska-Bienkowska et al. 2006; Steiner 1979; Steiner et al.
2001). However, the present study evaluated the facially
expressed emotions evoked by the basic tastes at different
sensory intensities in a comparative manner. The observations
of this study were in general agreement with previous work on
facial reactions as responses to basic tastes. The unpleasant
stimuli such as bitter taste or high intensities of salty or sour
tastes evoked stronger facially expressed emotions than pleasant and neutral stimuli such as sweet and umami tastes (Hu
et al. 1999; Rozin 2006; Steiner 1979; Zeinstra et al. 2009).
Among the different taste responses in this study, it was
evident that disgust received the highest ratings. Disgust has
indeed been considered as an emotion with a strong and
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Table 3 Pearson’s correlations of
the observed basic emotions and
the facial reactions (FACS) found
in the previous study by Wendin
et al. (2011), values in italics indicate significance, p≤0.05
Facial reaction
Facially expressed emotion
Happiness
Sadness
Anger
Disgust
Contempt
Surprise
Fear
Frown
0.109
0.713
0.943
0.990
0.916
0.747
0.806
Eye widening
Eye diminishing
Nose wrinkle
Nostril widening
Lips pressed
Lips pursed
Lip corner up
Lip corner down
Mouth open
Tongue out
0.513
−0.032
0.137
0.020
−0.143
0.373
−0.034
−0.001
0.130
−0.197
0.281
0.757
0.595
0.548
0.021
0.049
−0.300
0.545
0.095
0.005
0.582
0.932
0.873
0.827
0.398
0.330
0.092
0.700
0.571
0.359
0.739
0.930
0.858
0.848
0.503
0.451
0.145
0.769
0.646
0.371
0.628
0.863
0.854
0.731
0.293
0.254
0.031
0.551
0.442
0.429
0.966
0.652
0.754
0.694
0.486
0.762
0.422
0.573
0.726
0.268
0.516
0.769
0.603
0.577
0.129
0.338
−0.170
0.560
0.332
0.227
characteristic facial expression (Rozin and Fallon 1987;
Greimel et al. 2006). There is support from other studies that
negative responses to disliked tastes are expressed more
strongly than positive responses towards liked tastes (Horio
2003). Negative taste responses are expressed more instantaneously and unambiguously (Greimel et al. 2006; Steiner
1973) and are less influenced by the existing emotional state
(Greimel et al. 2006). They are thus often deemed easier to
distinguish and identify than positive responses to taste.
Higher concentrations of the taste solutions evoked greater
intensities of facially expressed emotions. The emotions were
not consistent across the basic tastes, e.g. the emotion surprise
was clearly observed for high concentrations of sour and bitter
solutions. While these were not the case for sweet, umami and
salty samples. Earlier studies have not taken into account the
variation of perceived intensity of taste solutions in relation to
different psychophysical functions of stimulus (Stevens 1969;
Janestad et al. 2000; Wendin et al. 2003). However, from the
results it is obvious that the intensity and type of emotions
elicited relate to the perceived intensity of the taste stimuli.
Nevertheless, the vigorousness of the facial expressed emotion remained generally low, even at the highest taste
intensities.
It was observed that the range of basic tastes in the present
study was rated relatively low on the degree of liking. Foods
can be expected to evoke greater positive affective responses.
Therefore, they may give more distinct facially expressed
emotions. Further studies with real foods may be considered
to confirm if the facial emotions could reveal more
information.
It was interesting to note that the greatest individual variation in facially expressed emotions was expressed for the
tastes that were rated as disliked. However, even if a taste was
disliked, the expected negative facial emotion was not necessarily expressed equally strong at the individual level. This
would suggest that a negative affect for a taste is not always
communicated facially by individuals. Other forms like verbal
expressions or other kinds of gestures may be more important
in conveying information about distaste. The absence of a
facially expressed emotion is not necessarily a predictor for
the absence emotions, but could be due to a lack of reason to
express, due to masking and control (Zeinstra et al. 2009) or
due to the emotional process itself not eliciting sufficient facial
activity to be interpretable to the observer (Tassinary and
Cacioppo 1992). Therefore, it is suggested that measurement
of the affective response for taste could include a wider
spectrum of observational and other methods than only the
facially expressed emotions.
A taste or a flavour in food may also elicit a sequence of
sensory experiences due to temporal changes in intensity
which may interact with emotions during tasting. For instance,
a reaction to a bitter stimulus could include surprise, followed
by disgust and perhaps further by anger and contempt. This is
in line with Lewis (2008), who concluded that emotions can
have anticipative, immediate and cognitive aspects. Clearly,
some emotions seem to be related to the anticipation of the
stimulus (e.g. surprise), whereas others seem to be driven by
the sensory experience itself and the subsequent cognitive
processing of the stimulus. More detailed studies are suggested to further address such dynamic features of taste and
flavour responses. The interactions with emotions evoked by
the specific context and environment could also be further
considered.
Conclusions
The perception of basic tastes revealed facial reactions and
facially expressed emotions, which were dependent on the
kind of taste quality. For most basic tastes, the severity of
the facial expressed emotions increased with the intensity of
the taste stimulus. Facially expressed emotions caused by
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Chem. Percept.
basic tastes were generally weak. Bitter, sour and salty gave
clear disgust and surprise responses, whereas, sweet and umami taste give weakly noticeable facial emotions. Although
correlations between the facial emotions and hedonic responses were observed, the affective experience had a limited
predictive ability for the facially expressed emotion at the
individual level. The study indicated that facially expressed
emotions in relation to moderate levels of basic taste perception alone are subtle. However, the variation encountered in
real foods may be more important for facial communication
and needs further investigation. The psychometric rating of
the liking response provides a more convenient way of gathering affective information of taste than analysing facial emotions. However, it may not completely represent the dimensionality of the emotions evoked by tasting.
Acknowledgments Bodil Allesen-Holm is greatly thanked for the
technical assistance in data management.
Compliance with Ethics Requirements
Conflict of Interest Wender L. P. Bredie declares that he has no conflict
of interest.
Hui Shan Grace Tan declares that she has no conflict of interest.
Karin Wendin declares that she has no conflict of interest.
All procedures followed were in accordance with the ethical standards
of the responsible committee on human experimentation (institutional and
national) and with the Helsinki Declaration of 1975, as revised in 2008
(5). Informed consent was obtained from all patients for being included in
the study.
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