Food Quality and Preference 18 (2007) 975–984
www.elsevier.com/locate/foodqual
The multisensory perception of flavor: Assessing the influence of
color cues on flavor discrimination responses
Massimiliano Zampini a,b,c,*, Daniel Sanabria c,d, Nicola Phillips e, Charles Spence c
a
Department of Cognitive Sciences and Education, University of Trento, Rovereto, Italy
b
Center for Mind/Brain Sciences, University of Trento, Rovereto, Italy
c
Department of Experiment Psychology, University of Oxford, South Parks Road, Oxford, England, UK
d
Departamento de Psicologı́a Experimental, Universidad de Granada, Spain
e
Unilever Research & Development Port Sunlight, Bebington, UK
Received 14 March 2006; received in revised form 30 March 2007; accepted 2 April 2007
Available online 14 April 2007
Abstract
Two experiments are reported that were designed to investigate the influence of visual color cues on people’s flavor discrimination and
flavor intensity ratings for a variety of fruit-flavored solutions. In Experiment 1, the participants had to associate specific flavors with
solutions of various colors simply by looking at them (i.e., without tasting them). In Experiment 2, the participants tasted the solutions
and had to discriminate the flavor of solutions that had been colored either ‘appropriately’ or ‘inappropriately’, or else presented as colorless solutions. The participants were explicitly informed that the colors of the solutions provided no useful information regarding the
actual flavor identity of the solutions. The participants also rated the flavor intensity of the solutions. The accuracy of participants’ flavor
discrimination performance was significantly lower when the solutions were colored inappropriately than when they were colored appropriately (or else were presented as colorless solutions). These results show that the modulatory effect of visual cues on flavor perception
can override participants’ awareness that the solutions would frequently be colored inappropriately.
Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: Flavor perception; Color; Visual dominance; Fruit-flavored beverages; Labelled magnitude scale (LMS)
1. Introduction
The perception and evaluation of food and drink is an
inherently multisensory experience. Gustatory, olfactory,
visual, oral-somatosensory, auditory, and even nociceptive
cues can all play a role in determining our perception of
what we eat and drink (see Delwiche, 2004; Spence, 2002;
Stillman, 2002). For instance, our perception of the pleasantness of a food is influenced not only by its look, smell,
and taste, but also by its oral texture and by the sound that
*
Corresponding author. Address: Department of Cognitive Sciences
and Education, University of Trento, Rovereto, Italy. Tel.: +39 0464
483604; fax: +39 0464 483554.
E-mail addresses: [email protected] (M. Zampini), [email protected] (C. Spence).
0950-3293/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.foodqual.2007.04.001
it makes in the mouth when we eat it (e.g., Amerine, Pangborn, & Roessler, 1965; Vickers, 1983; Zampini & Spence,
2004, 2005). Flavor perception is also influenced by interactions between oral texture and both olfactory and gustatory cues. For example, Christensen (1980a, 1980b) has
demonstrated that changes in the viscosity of a solution
can modify its perceived taste and flavor and vice versa
(see also Bult, de Wijk, & Hummel, 2007).
The visual appearance of food and drink can also provide another important determinant of flavor perception.
Over the years, many different researchers have attempted
to evaluate the influence of color cues on people’s flavor
perception (see Clydesdale, 1993; Delwiche, 2004; for
reviews). Color cues have been shown to dramatically affect
people’s perception of a variety of different foods and
drinks (e.g., DuBose, Cardello, & Maller, 1980; Duncker,
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M. Zampini et al. / Food Quality and Preference 18 (2007) 975–984
1939; Garber, Hyatt, & Starr, 2000; Johnson & Clydesdale,
1982; Morrot, Brochet, & Dubourdieu, 2001; Philipsen,
Clydesdale, Griffin, & Stern, 1995; Roth, Radle, Gifford,
& Clydesdale, 1988; Stillman, 1993; Wheatley, 1973; Zellner & Durlach, 2003). For example, in one oft-cited study,
DuBose et al. reported that participants were less accurate
in identifying the flavor of a fruit-flavored beverage when
they were unable to perceive its color (e.g., 20% correct flavor detection responses in the masked color condition vs.
100% correct responses under normal viewing conditions
for an orange-flavored beverage). More importantly, 40%
of the participants reported that a cherry-flavored beverage
actually tasted of orange when the beverage was inappropriately colored orange (compared to 0% orange-flavor
responses when the drink was appropriately colored red).
Other researchers have also reported a similar visual modulation of odor discrimination responses (e.g., Blackwell,
1995; Davis, 1981; Zellner, Bartoli, & Eckard, 1991; Zellner
& Kautz, 1990; Zellner & Whitten, 1999).
While the potential influence of color cues on flavor
identification responses is by now well-documented, the
evidence regarding the impact of changes in color intensity
on perceived flavor intensity is less clear. For instance, the
addition of a red coloring to cherry- and strawberry-flavored sucrose solutions has been found to increase the perceived sweetness of these solutions (Johnson & Clydesdale,
1982; Johnson, Dzendolet, & Clydesdale, 1983; Johnson,
Dzendolet, Damon, Sawyer, & Clydesdale, 1982). Furthermore, a number of years ago, Maga (1974) made the
intriguing suggestion that those colors that are typically
associated with the natural ripening of fruits (e.g., red, yellow, etc.) may be particularly effective in modulating sweetness perception (see also Strugnell, 1997). However, Frank,
Ducheny, and Mize (1989) found that strawberry odor, but
not red color, affected sweetness perception in their study.
In one of the earliest studies in this area, Pangborn
(1960) reported that people perceived a green-colored pear
nectar as being less sweet than a colorless pear nectar.
However, Pangborn and Hansen (1963) failed to replicate
these results, instead reporting that green coloring had no
effect on the perceived sweetness of pear nectar, despite
an overall increase in sensitivity to sweetness when color
was added to the solutions. Ambiguous results have also
been reported in studies where participants have been
asked to rate the flavor intensity of solutions varying in
the intensity of the color added. DuBose et al. (1980) also
found that overall flavor intensity was affected by color
intensity, with higher levels of color intensity resulting in
stronger flavor evaluation responses by participants for
the orange-flavored but not for the cherry-flavored beverages tested in their study (see Clydesdale, 1993; for a comprehensive review).
At present, no clear explanation has been provided for
the lack of convergent results between studies that have
investigated the influence of color intensity on flavor perception. It is possible that the lack of convergence might
reflect the use of inadequate scaling procedures for rating
taste or flavor intensity in many of the previous studies
in this area. One plausible suggestion here is that a more
consistent pattern of responding might have been observed
if a more sophisticated means of rating perception were to
be used, such as that embodied by the Labelled Magnitude
Scale (LMS; Green, Shaffer, & Gilmore, 1993). The LMS is
a semantically-labelled scale with a quasi-logarithmic spacing between the verbal labels that has been specifically
developed for the rating of gustatory and oral-somesthetic
sensations. The LMS has the characteristics of a category
scale (i.e., a presentation that is easily accepted by naı̈ve
participants) yielding data with ratio-level properties. The
LMS is usually presented as a vertical line with its upper
limit labelled ‘‘strongest imaginable” and the lower limit
‘‘no sensation” (the intermediate labels are: ‘‘very strong”,
‘‘strong”, ‘‘moderate”, ‘‘weak”, ‘‘barely detectable”). In a
typical study using the LMS, participants have to rate
the intensity of a stimulus by comparing it with all other
stimuli found in daily life along this vertical line.
Unlike other magnitude scales, the LMS reduces the
possibility of ceiling effects by using the ‘‘strongest imaginable” adjective as the upper limit, thus not limiting one to a
fixed number range (e.g., Bartoshuk, 2000). Furthermore,
Green et al. (1993) have argued that the use of more traditional numerical scaling methods (e.g., magnitude estimation), can emphasize inter-individual differences, due to
people’s idiosyncratic usage of numbers. This problem is
reduced when participants use the LMS scale. Moreover,
Kurtz and White (1998) have shown that the evaluation
of complex stimuli such as flavors is particularly stable
between raters using the LMS.
The primary aim of our main experiment (Experiment 2)
was to investigate the influence of color intensity on the
perception of flavor intensity using the LMS procedure.
The LMS procedure has never been used for this kind of
task before, and given that it seems more suitable than
other scaling procedures, we thought that its use might help
to reduce some of the discrepancies highlighted amongst
previous research in this area. However, before investigating the impact of color on flavor perception directly, an initial experiment was conducted in order to analyze people’s
expectations concerning flavor based solely on visible color
cues. In Experiment 1, the participants were asked to simply identify the flavor that was most closely associated for
them with the color of the solutions presented by inspecting
them visually (but without tasting them). The aim of this
preliminary study was to determine whether there are certain colors that are more reliably associated with one flavor
than with another. The hypothesis was that these colors
might have a greater impact on flavor perception in our
main experiment (Experiment 2) where participants evaluated the solutions by both viewing and tasting them. It
seemed plausible that this factor – the different color–flavor
associations held by different individuals – might also help
to explain the inconsistent effect of color intensity on flavor
intensity ratings that have been documented in previous
studies.
M. Zampini et al. / Food Quality and Preference 18 (2007) 975–984
2. Experiment 1
2.1. Methods
2.1.1. Participants
Eleven female participants aged between 25 and 42 years
(mean age of 34 years) took part in both of the experiments
reported here. All of the participants were naı̈ve as to the
purpose of the study, and varied in their previous experience of psychophysical testing procedures. The participants
were selected from a panel of untrained individuals
recruited from the staff at Unilever Research & Development Port Sunlight. All of the participants reported having
normal gustatory and olfactory abilities and normal, or
corrected-to-normal, vision. All of the participants had
normal color-vision as assessed by means of the Ishihara
test for color blindness (Ishihara, 1943). None of the participants reported having a cold or other respiratory tract
infection either on the days of the testing sessions or in
the week prior to testing. The participants gave their
informed consent prior to the start of the experiment. Both
of the experiments reported in this study had ethical
approval from Unilever Research & Development Port
Sunlight Laboratory. The participants received £20 gift
voucher each in return for taking part in the study.
2.1.2. Apparatus and stimuli
The participants were seated comfortably in front of a
table in an individual testing booth at the Port Sunlight
testing facilities. The participants were given a transparent
plastic cup of a flavorless solution (40 ml) on each trial.
The solutions were colored red, green, orange, yellow, blue,
grey, or else were colorless. The solutions were prepared
from 1 l of distilled water by adding concentrated food colorings (Supercook, Leeds, UK): 16 ml of yellow food coloring for the yellow solutions; 16 ml of blue food
coloring for the blue solutions; and 16 ml of red food coloring for the red solutions. The green solutions were
obtained by mixing 4 ml of blue food coloring with 8 ml
of yellow food coloring; the orange samples by adding
8 ml of red and 16 ml of yellow; and the grey samples by
adding 8 ml of yellow, 8 ml of red, and 20 ml of the blue
food coloring. All of the food colorings used in the present
study were flavorless. The colorless samples consisted of
distilled water and nothing else.
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2.1.3. Design
The one within-participant factor was the color of the
solutions (red, green, orange, yellow, blue, grey, or colorless). Each of the seven colored solutions was presented 5
times within a single block of 35 randomly-ordered trials.
The experiment lasted for approximately 30 min.
2.1.4. Procedure
The participants were given written instructions describing the experimental procedure to read in their own time.
The experimenter then explained the procedure to the participants and demonstrated the equipment. The participants were instructed to look at each solution from
above, and to identify the flavors that they perceived as
corresponding most closely to the color of the solution.
They had to indicate their response by making a tick on
a list using a paper-based response sheet. The following
options were available on the list: Strawberry, pear, lemon,
melon, lime, orange, aniseed, spearmint, liquorice, cherry,
lettuce, vanilla, toffee, cream soda, apple, peach, raspberry,
pineapple, yoghurt, blackcurrant, flavorless, or other. If
participants indicated this last option they were prompted
to suggest the specific flavor that they had in mind. The
participants were also informed that they could choose
the same option on more than one occasion. No time limits
were imposed for the completion of a participant’s
responses.
2.2. Results and discussion
The analyses reported in this study were conducted
using SPSS (SPSS Inc., Chicago, USA). Participants’
responses to each of the colored solutions were analyzed
using v2 analysis. The results (summarized in Table 1)
showed that participants more often associated the green
colored solutions with lime flavor (M = 69%), the orange
colored solutions with an orange flavor (M = 91%), the yellow solutions with the lemon flavor (M = 89%), the blue
solutions with spearmint flavor (M = 86%), the grey solution with the flavor of blackcurrant (M = 53%) or liquorice
(M = 40%), and the colorless solution with the flavorless
response (M = 51%). Finally, it is important to note that
the red coloring was not especially associated with any particular flavor (i.e., strawberry, M = 46%, raspberry, and
cherry flavor both M = 27%) over the others (although
Table 1
Results of v2 analysis for each of the colors used in Experiment 1
Color
v2
p
Associated flavors
Green
Orange
Yellow
Blue
Grey
Red
Colorless
32.33
82.01
120.64
67.34
41.94
3.64
69.85
<.001a
<.001a
<.001a
<.001a
<.001a
.16
<.001a
Lime (69%) > apple (20%), melon (11%)
Orange (91%) > aniseed (5%), toffee (4%)
Lemon (89%) > pear (5%), apple (4%), melon (2%)
Spearmint (86%) > raspberry (9%), cream soda (5%)
Blackcurrant (53%), liquorice (40%) > cherry (4%), aniseed (4%)
Strawberry (46%), rasperry (27%), cherry (27%)
Flavorless (51%) > cream soda (16%), vanilla (15%), aniseed (15%), spearmint (2%), melon (2%), pear (2%)
a
Significant post-hoc comparisons (Bonferroni corrected with p = .05 before comparison) to test for particular color–flavor associations are shown in
the last column together with the percentage of choices for each flavor.
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M. Zampini et al. / Food Quality and Preference 18 (2007) 975–984
note that this finding does not necessarily rule out the possibility that the red color may actually have had an equally
strong association with several of the flavor terms on the
list provided).
The results of Experiment 1 demonstrate that solutions
having certain colors are strongly associated with particular flavors. The orange, yellow, and blue solutions were frequently associated with the flavors of orange, lemon, and
spearmint, respectively. There was more variability in the
flavor associations generated for the red solutions: Participants typically associated the red solutions with the flavors
of strawberry, raspberry, and cherry. It would seem reasonable to suggest that colored solutions whose color is more
robustly associated with one particular flavor should have
a greater influence on flavor identification responses when
participants actually taste the solutions than for colored
solutions where the color–flavor link is less apparent (or
is less commonly shared). This hypothesis was investigated
in the second experiment by presenting fruit-flavored solutions (orange, lime, and strawberry) each colored green,
orange, or red. Preliminary testing had revealed that these
three flavors were roughly equally identifiable.1 The question of whether or not the intensity of the color would
influence the perception of flavor intensity was also investigated using a LMS procedure that had been specifically
designed to evaluate oral sensation (e.g., Green et al.,
1993).
In Experiment 2, all of the participants were explicitly
informed that the flavored solutions would frequently be
colored ‘inappropriately’. This experimental manipulation
allowed us to investigate whether or not the visual cues
would still influence flavor perception when the participants were aware of the lack of any meaningful correspondence between color and flavor. To our knowledge, this
issue has never been addressed previously in research on
the influence of color cues on flavor perception.
3. Experiment 2
3.1. Methods
3.1.1. Apparatus and stimuli
The participants were seated in front of a disinfected
sink (the disinfectant used was odorless) and received a
1
Participants were presented with colorless solutions having the
following flavors: strawberry, lime, orange, blackcurrant, yoghurt, apple,
raspberry, and flavorless. The participants were instructed to taste the
solutions by moving the liquid around in their mouths, but not to swallow
at any stage. The participants were asked to spit the solutions into the
provided sink. Next, participants were asked to identify the flavor of the
solution, by ticking a list (the options were the same as those used in
Experiment 1). Finally, they were asked to rinse their mouths thoroughly
with artificial saliva, without swallowing, and spit this into the sink
provided. The accuracy of participants’ responses was as follows:
flavorless (89%), apple (65%), strawberry (40%), lime and orange (33%),
blackcurrant (20%), raspberry (15%) and finally yoghurt (12%).
plastic cup of colored and flavored solution on each trial.
The plastic cups were transparent and specifically designed
for food use. The solutions were presented at room temperature (20 ± 2 °C). The solutions in this experiment were
colored red, green, or orange. Strawberry (House of Flavors, reference: 01/10114), lime (01/10071), and orange
(01/10085) fruit flavors were used. The solutions were prepared by adding 1.5 ml of concentrated fruit flavor to each
litre of distilled water used. In each litre of solution, 62.5 g
of sucrose (GMP sugar, Aarhus United, Hull, UK) was
dissolved.
Each of the flavorings was equiprobably associated with
each of the different colors (red, green, orange, and colorless). This meant that, for example, the strawberry flavored
solutions were just as likely to be colored red, green,
orange, as to be presented as a colorless solution. Consequently, the color of the solutions did not have any predictive validity regarding the likely flavor of the solutions
being tasted. The participants were told that they would
often be tricked by the color of the solutions (i.e., that
the color of the solutions would often not correspond to
the flavor typically associated with that color). All of the
participants were explicitly informed that the colors of
the solutions that they were to taste provided absolutely
no useful information with regard to the likely flavor of
the solutions (i.e., that the colors and flavors were fully
crossed in the experimental design). Flavorless samples
were also presented and they could be colored or colorless
just as for the flavored solutions.
The volume of coloring added to the solutions varied
between either a standard concentration (i.e., 8 ml of red
coloring for the red solutions; 2 ml of blue coloring and
4 ml of yellow coloring for the green solutions; and 4 ml
of red coloring and 8 ml of yellow coloring for the orange
solutions) and a double concentration (i.e., by doubling the
volumes of each of the colorings added). The bottled liquids were prepared on the morning of the study, used during the day and discarded at the end of the day. The
experimenter dispensed 40 ml of the solutions from the airtight glass bottles into the clear plastic cups immediately
prior to testing using a sterile syringe. The cups were sealed
during the period between the dispensing of the liquids and
the beginning of the experimental testing session.
The experimenter gave participants 40 ml of flavorless
palate cleansing solution (‘artificial saliva’) between each
trial in order to wash their mouths out before tasting the
next beverage. This palate cleansing solution was made
from deionised water, 1.865 g/l of potassium chloride
(KCl), and 0.210 g/l of sodium bicarbonate (NaHCO3;
see O’Doherty, Rolls, Francis, Bowtell, & McGlone,
2001), and was stored in separate glass bottles from the flavored solutions.
3.1.2. Design
There were three within-participants factors: The flavor
of the solutions (strawberry, lime, orange, or flavorless),
M. Zampini et al. / Food Quality and Preference 18 (2007) 975–984
the color of the solutions (red, green, orange, or colorless),
and the amount of food coloring added (standard or double). These factors were fully crossed (with the exception
that the volume of coloring had no meaning for the colorless solutions) resulting in 28 conditions, which were each
presented 4 times. The colored samples were added to the
colorless–flavorless samples (which were presented 12
times) resulting in a block of 124 randomly-ordered trials
in total. The experimental session lasted for approximately
90 min.
3.1.3. Procedure
The participants were given both written and oral
instructions to view the solutions from directly above the
plastic cup and then to taste them by moving the liquid
around in their mouth, but not to swallow the liquid at
any stage.2 After tasting each of the solutions, the participants were asked to spit the solutions into the sink provided. The participants were instructed to try and
determine the identity and intensity of the flavor, bearing
in mind that these might have been manipulated so that
the color should not be considered to provide a reliable
cue to flavor identity. After having tasted each solution,
the participants were instructed to indicate the flavor that
they perceived by ticking an answer sheet (the options were
the same as in Experiment 1) and to evaluate their perception of flavor intensity for each solution using the LMS
(e.g., Green et al., 1993). The participants were fully
informed and trained (but not experienced) in the use of
the scale. In particular, they were instructed on how to
interpret the verbal descriptors (e.g., strongest imaginable
sensation). They were then asked to rinse their mouths
thoroughly with the palate cleansing solution, again without swallowing, and to spit this into the sink provided
before testing the next solution.
3.2. Results
The data regarding flavor identification responses from
Experiment 2 are highlighted in Fig. 1. The accuracy data
regarding participants’ flavor detection responses were submitted to a two-way within-participants repeated-measures
ANOVA with the factors of Flavor (flavorless, lime,
orange, or strawberry) and Color (colorless, green-standard, green-doubled, orange-standard, orange-doubled,
2
The principal reason for instructing the participants not to swallow
was that they might have found it rather unpleasant to potentially drink
such a large quantity of liquid. The participants actually tasted 124
cups 40 ml = about 5 l of liquid in total. However, it is important to
note on this point that previous studies have shown that people can vary
quite considerably in terms of the retro-nasal delivery of odors/flavors
when swallowing is prevented (see Buettner, Beer, Hannig, & Settles, 2001;
Hodgson, Linforth, & Taylor, 2003). The fact that the participants did not
swallow the drinks in the present study represents one limitation in terms
of the ecological validity of our experimental design given that people
normally swallow the beverages/foodstuffs that they put in their mouths.
979
red-standard, or red-doubled). For all of the analyses
reported here, post-hoc comparisons used Bonferroni-corrected t-tests (where p < .05 prior to correction). The analysis of the accuracy data revealed a significant main effect
of Flavor (F(3, 30) = 5.49, p < .005), reflecting the fact that
participants detected the flavorless solutions (mean of 93%
correct ‘flavorless’ responses) more accurately than when
they were lime- (M = 55%), orange- (M = 62%) or strawberry-flavored (M = 51%; none of the post-hoc comparisons between the flavored solutions reached significance).
The significant interaction between Flavor and Color
(F(18, 180) = 5.01, p < .001), revealed that the lime-flavored solutions were identified more accurately when they
were colored green-standard (M = 73%), green-doubled
(M = 70%) or were colorless (M = 73%) than when they
were colored orange-standard (M = 54%), orange-doubled
(M = 31%), red-standard (M = 45%), or red-doubled
(M = 36%). Moreover, the orange flavor was detected
more accurately in solutions that were colored orange-standard (M = 82%), orange-doubled (M = 79%), or colorless
(M = 69%) than in either the green-standard (M = 45%),
green-doubled (M = 50%), red-standard (M = 60%), or
red-doubled (M = 48%) colored solutions (the post-hoc
comparisons between the orange and colorless solutions
and between the green and red solutions were not significant). The accuracy with which the participants were able
to detect the strawberry-flavored solutions was unaffected
by their color (M = 56% for red-standard; M = 59% for
red-doubled; M = 47% for green-standard; M = 49% for
green-doubled; M = 46% for orange-standard; M = 53%
for orange-doubled; and M = 48% for the colorless
solutions).
There was a borderline-significant main effect of Color
(F(6, 60) = 2.17, p = .058), with participants detecting the
flavors of the solutions more accurately when they were
colorless (M = 72%), orange-standard (M = 68%), orangedoubled (M = 66%), than when they were colored red-doubled (M = 58%; however, note that none of the post-hoc
comparisons between these conditions were significant).
A similar ANOVA was performed on the flavor intensity LMS ratings (see Fig. 2). The participants’ individual
mean responses were log 10-transformed before conducting
this analysis because the distribution of LMS ratings is typically log-normal (Green & George, 2004). The analysis of
the flavor intensity log 10-converted data revealed a significant main effect of Flavor (F(3, 30) = 77.22, p < .001),
attributable to the fact that participants rated the intensity
of the flavorless solutions (mean rating of – 1.150) as being
significantly weaker than the lime (M = 1.295), orange
(M = 1.118), or strawberry (M = 1.355) solutions, as might
have been expected. There was also a significant difference
between the strawberry- and orange-flavored solutions
with the strawberry solutions being rated as having a more
intense flavor than the orange solutions. There was no significant difference between the intensity ratings for the
orange- and lime-flavored solutions, nor for the comparison between the lime- and strawberry-flavored solutions.
980
LIME
100
c 100
75
75
Correct responses (%)
Correct responses (%)
a
M. Zampini et al. / Food Quality and Preference 18 (2007) 975–984
50
25
0
STRAWBERRY
50
25
0
Greenstandard
Greendoubled
Orangestandard
Orangedoubled
Redstandard
Reddoubled
Greenstandard
Colorless
Greendoubled
Color of the solutions
Orangestandard
Redstandard
Reddoubled
Colorless
Reddoubled
Colorless
Color of the solutions
ORANGE
FLAVORLESS
d 100
75
75
Correct responses (%)
b 100
Correct responses (%)
Orangedoubled
50
25
50
25
0
0
Greenstandard
Greendoubled
Orangestandard
Orangedoubled
Redstandard
Reddoubled
Colorless
Color of the solutions
Greenstandard
Greendoubled
Orangestandard
Orangedoubled
Redstandard
Color of the solutions
Fig. 1. Mean percentage of correct flavor detection responses for the lime (a), orange (b), strawberry (c), and flavorless (d) solutions presented in
Experiment 2. The error bars represent the between-participants standard errors of the means.
There was no main effect of Color [F(6, 60) = 1.18,
p = .33], although the interaction between Flavor and
Color was significant [F(18, 180) = 2.84, p < .001]. This
interaction reflects the fact that participants rated the
lime-flavored solution as having a less intense flavor when
the color was double orange (M = 1.095) than when the
solutions were uncolored (M = 1.394) or the color was
standard orange (M = 1.371). No effect of color intensity
was found for either the green or red colored lime-flavored
solutions (standard green coloring, M = 1.318; double
green coloring, M = 1.327; standard red coloring,
M = 1.298; and double red coloring, M = 1.260).
3.3. Discussion
The most important finding to emerge from Experiment
2 was that color cues can modulate flavor identification
responses even when participants are informed that these
colors will often be misleading. In particular, flavors associated with inappropriate colors (i.e., lime-flavored drinks
that were colored either red or orange; orange-flavored
drinks that were colored either green or red) were perceived
less accurately than when they were presented with the
appropriate color (i.e., lime flavor–green color; orange fla-
vor–orange color). These results appear to show that inappropriate coloring tended to lead to an impairment of
flavor discrimination responses, while appropriate coloring
did not improve flavor discrimination accuracy (at least
when compared to the flavor discrimination accuracy for
the colorless solutions). Interestingly, no significant effect
of color was shown for the strawberry-flavored solutions.
The identification of strawberry flavor did not decrease
when the solutions were colored incongruently (i.e., when
strawberry-flavored solutions were colored green or
orange). Finally, it is worth noting that adding color to flavorless solutions never induced significant ‘illusory’ flavor
responses (cf. Zellner & Kautz, 1990).
Another finding to emerge from Experiment 2 was that
increasing the intensity of the color of the solutions did not
result in an increase of participants’ flavor intensity evaluations. That is, the participant did not rate the double colored solutions as having a flavor that was significantly
more intense than the standard colored solution. The concentration of coloring in the solutions did not influence
participants’ ratings either when the solutions were appropriately colored or when they were inappropriately colored
(cf. Johnson et al., 1982, 1983). It is worth noting that this
null effect of color intensity on flavor intensity emerged
despite the fact that an LMS scale, a rating procedure that
M. Zampini et al. / Food Quality and Preference 18 (2007) 975–984
c
LIME
1. 2
Perceived flavor intensity (log10)
Perceived flavor intensity (log10)
a 1. 6
0. 8
0. 4
0
-0 .4
-0 .8
-1 .2
981
STRAWBERRY
1. 6
1. 2
0. 8
0. 4
0
-0 .4
-0 .8
-1 .2
-1 .6
-1 .6
-2
-2
Greenstandard
Greendoubled
Orangestandard
Orangedoubled
Redstandard
Reddoubled
Greenstandard
Colorless
Greendoubled
Color of the solutions
b
Orangestandard
Orangedoubled
Redstandard
Reddoubled
Colorless
Reddoubled
Colorless
Color of the solutions
d 1. 6
ORANGE
FLAVORLESS
Perceived flavor intensity (log10)
Perceived flavor intensity (log10)
1. 6
1. 2
0. 8
0. 4
0
-0 .4
-0 .8
-1 .2
1. 2
0. 8
0. 4
0
-0 .4
-0 .8
-1 .2
-1 .6
-1 .6
-2
-2
Greenstandard
Greendoubled
Orangestandard
Orangedoubled
Redstandard
Reddoubled
Colorless
Color of the solutions
Greenstandard
Greendoubled
Orangestandard
Orangedoubled
Redstandard
Color of the solutions
Fig. 2. Mean log 10 flavor intensity ratings for the lime (a), orange (b), strawberry (c), and flavorless (d) solutions presented in Experiment 2. The error
bars represent the between-participants standard errors of the means.
has been argued to be less influenced by inter-individual
differences between participants (see Green et al., 1993;
Kurtz & White, 1998; this point will be discussed further
below), was used.
4. General discussion
The results of Experiment 1 demonstrated that solutions
of certain colors are more often associated with particular
flavors (than with the other flavor options presented on the
flavor list) when people had to link the color of the solution
with a flavor by inspecting it visually (but without tasting
it). In particular, green-colored solutions were associated
with lime flavor, the orange-colored solution with an
orange flavor, the blue-colored solutions were frequently
associated with a spearmint flavor, and the yellow-colored
solutions with a lemon flavor (see Table 1). By contrast, the
red- and grey-colored solutions were not so strongly associated with any particular flavor (rather, the red color
appeared to have equally strong associations with a number of the flavor options that were provided on the
response list). The participants associated red-colored solutions with the flavor of strawberry, raspberry, and cherry,
while the grey-colored solutions were associated with the
flavors of blackcurrant and liquorice more often than with
any of the other flavors.3
The results of Experiment 2 showed that it is possible to
impair flavor discrimination performance by coloring fruitflavored solutions inappropriately (cf. DuBose et al., 1980).
In particular, the lime- and orange-flavored solutions were
discriminated less accurately when the solutions were colored inappropriately (i.e., lime-flavored solutions colored
orange or red, and orange-flavored solutions colored green
or red). By contrast, the discrimination of strawberry flavor
was not affected by the color of the solutions. That is, the
inappropriate coloring of the strawberry-flavored solutions
did not reduce the participants’ ability to recognize the
actual flavor. One possible explanation for this result is
that those flavors that are more strongly associated with
3
It is worth highlighting the possibility that the list of flavors provided
to participants in the present study might have influenced the profile of
their responses. In particular, it is possible that the specific color/flavor
associations reported in Experiment 1 might to some extent have been
prompted by the options available on the response list given to
participants. For instance, there were many realistic, commonly available
flavor options on the list that could be associated with the red color (e.g.,
apple, cherry, raspberry, strawberry, apple). By contrast, there were fewer
possible flavor options that could sensibly be associated with the orange
color.
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M. Zampini et al. / Food Quality and Preference 18 (2007) 975–984
a color are more difficult to identify when presented in
inappropriately colored solutions. The results of Experiment 1 demonstrated that the relationship between color
and a specific flavor was stronger for the orange- and
green-colored solutions than for the red-colored solutions.
That is, the participants more often matched the orange
color with the flavor of orange and the green color with
the flavor of lime. By contrast, the red color was associated
with strawberry, raspberry and cherry flavors. The results
of Experiment 2, demonstrating the effect of inappropriate
food coloring on orange- and lime-flavored solutions but
not on strawberry-flavored solutions, would therefore seem
to confirm the view that inappropriate colors decrease the
detection of flavor only when there is a strong flavor–color
association.
It is important to note that the present results show that
people can still be misled by the inappropriate coloring of a
solution even if they know that the color does not provide a
reliable guide to the flavor of the solution. By contrast, the
participants in the majority of previous research in this
area (e.g., DuBose et al., 1980; Johnson & Clydesdale,
1982; Morrot et al., 2001; Oram et al., 1995; Philipsen
et al., 1995; Roth et al., 1988; Stillman, 1993; Zellner &
Durlach, 2003) were not explicitly informed that the flavors
of the solutions might not be paired with the appropriately
colored solutions. It can therefore be argued that the
apparent visual influence over flavor perception reported
in many of these earlier studies might simply have reflected
a decisional bias introduced by the obvious variation in the
color cues (cf. the literature on the effectiveness of the color
of medications on the placebo effect; e.g., de Craen, Roos,
de Vries, & Kleijnen, 1996), rather than a genuine perceptual effect (i.e., of the color cues actually modulating flavor
perception itself; though see also Garber, Hyatt, & Starr,
2001; for an alternative perspective from the field of marketing). In other words, if participants found it difficult
to discriminate the identity of the flavor on the basis of gustatory and olfactory cues then they may simply have
decided to respond on the basis of the more easily discriminable color cues instead. Therefore, it might be hypothesized that participants in these previous studies may have
been influenced by decisional processes, whereas the design
of the present experiment was more focused on uncovering
any genuinely perceptual interactions by explicitly informing participants that the color–flavor link would often be
misleading (i.e., that the solutions would frequently be presented in an inappropriate color; cf. Bertelson & Aschersleben, 1998). The results of Experiment 2 show that the
modulatory role of visual information on multisensory flavor perception was so robust as to override any awareness
that participants might have had (e.g., as informed by the
experimenter) about the possibility that solutions were colored inappropriately.
The second important result to emerge from the analysis
of Experiment 2 was that changing the intensity of the colors added to the solutions did not change participants’ perception of flavor intensity even when the participants made
their intensity rating responses using the LMS. The participants were not influenced by the different concentration of
coloring in the solutions, either when the color was appropriate to the flavor or when it was not. As noted in Section
1, contradictory results have also been reported by
researchers in previous studies regarding the influence of
variations in color intensity on the perception of taste
and flavor intensity, with some researchers reporting that
perceived flavor intensity could be enhanced by increasing
the level of color intensity (e.g., DuBose et al., 1980; Johnson & Clydesdale, 1982; Johnson et al., 1982, 1983; Pangborn, 1960); whereas others failed to confirm these results
(e.g., Frank et al., 1989; Pangborn & Hansen, 1963; see
Clydesdale, 1993; for a review).
In Section 1, it was argued that one possible reason for
the discrepancy reported in previous studies was that a
numerical scale was used for rating taste or flavor intensity
in all of the studies. As has been noted elsewhere, the use of
such scales appears to be somewhat limited. In particular,
greater inter-individual differences have been reported
when numerical scaling methods are used, presumably
because of the idiosyncratic number usage encouraged by
the use of such scales (e.g., Green et al., 1993). Moreover,
ceiling effects are often reported in studies using numerical
scales and this can make the interpretation of results more
difficult (Bartoshuk, 2000). In the present study, these
methodological limitations were overcome by using an
LMS to assess flavor intensity ratings (Bartoshuk, 2000;
Green et al., 1993). Nevertheless, no effect of variations
in color intensity on flavor intensity ratings by the participants were found (see the results of Experiment 2).
It should also be noted that the results show quite a low
variance for each flavor/color combination. It could be
argued that this result might reflect a problem associated
with the convergence of responses that has sometimes been
reported to occur when using LMS scales. In particular, it
has been pointed out that the use of the ‘Strongest Imaginable’ label has a tendency to suppress intensity ratings constraining them to a relatively small portion of the response
scale (e.g., see Bartoshuk, Fast, & Snyder, 2005). Therefore, the possibility cannot be unequivocally ruled out that
the use of the LMS scale by participants in the present
study might have been in part responsible for the lack of
effect of color intensity on flavor intensity ratings. Future
studies should seek to address this issue.
It is, however, worth noting that more intense coloring
does not necessarily always equate with increased flavor
intensity ratings in beverages. For example, Chan and
Kane-Martinelli (1997) reported that the perceived flavor
intensity for certain foods (such as chicken bouillon) was
higher with the commercially available color sample than
when the samples were given in a higher-intensity color
(see also Clydesdale, 1993; on this point). Note also that
if the discrepancy between the intensity of the color and the
intensity of the flavor is too great participants may experience a disconfirmation of expectation (or some form of dissonance between the visually- and gustatorily-determined
M. Zampini et al. / Food Quality and Preference 18 (2007) 975–984
flavor intensities) and the color and taste cues will no
longer be linked (e.g., Clydesdale, 1993; cf. Ernst & Banks,
2002).
Finally, it is also worth noting that the colors that are
present in food and drinks (such as in the fruit-flavored
solutions presented in the current study) might affect people’s flavor identification at both a perceptual and at a
more semantic level. With regard to the nature of any
semantic interactions between visual cues and flavor perception, the notion of redness could presumably be communicated to participants either by coloring the drink
red, or else by packaging the drink in a red container
(e.g., see Garber et al., 2000; Hine, 1995; Spence, 2007),
or even by viewing the word red (cf. Demattè, Sanabria,
& Spence, 2006; on this point). In future research, it will
be interesting to discriminate between genuinely perceptual versus semantic crossmodal interactions in flavor
perception.
Acknowledgements
This investigation was supported by a research grant
from Unilever Research & Development. M.Z. was also
supported by a returning grant ‘‘Rientro dei cervelli” from
the MIUR (Italy).
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