The Huron University College Journal of Learning and
Motivation
Volume 45 | Issue 1
Article 5
2007
Cross Modality Priming: The Effect of Odor
Primes on the Stroop Task
Talia Dick
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Dick, Talia (2007) "Cross Modality Priming: The Effect of Odor Primes on the Stroop Task," The Huron University College Journal of
Learning and Motivation: Vol. 45: Iss. 1, Article 5.
Available at: http://ir.lib.uwo.ca/hucjlm/vol45/iss1/5
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Stroop Task in Pleasant and Unpleasant Conditions
Cross Modality Priming: The Effect of Odor Primes on the Stroop Task
Talia Dick
Huron University College
A study was conducted to investigate the effect
of odor primes on the Stroop phenomenon. If an
appropriate prime gives a particular cue to a colorword stimulus, the reaction time is faster and if it's
inappropriate, the reaction is slower. Odor primes
(pleasant vs. unpleasant) should effect performance
on the Stroop task for both words that are congruent to
the particular odor, and incongruent to an odor. 40
undergraduate students at a Canadian university
were randomly assigned to one of four conditions, and
were administered a modified Stroop task. Participants
in the first two conditions were tested in the presence of
a pleasant scent and either tested with pleasant or
unpleasant words. Participants in the last two conditions
were tested in the presence of an impleasant scent and were
either tested with pleasant or unpleasant words. Performance
was measured by the time it took to complete the Stroop
task. A 2 X 2 between subjects ANOVA was performed and
insignificant main effects and interaction effects were found.
Implications for future studies and research are addressed.
For normal adults, color reading is a much faster process than color naming.
Simply, it is much easier to read the word "red," than to name a particular color patch
"red." Based on this notion, Cattell (1886) argued that adults simply have more practice
and experience with reading over naming. This sparked a great interest within John
Ridley Stroop, an American Psychologist, who suggested that if both reading and naming
are parallel mental processes, color naming might interfere with color reading when the
two are in conflict with each other (Pauli, Bourne, Diekmann & Birbaumer, 1999). He
believed that if a color-word stimulus was written in a different color ink, individuals
would have more trouble naming the ink color, as they should be more inclined to read
Stroop Task in Pleasant and Unpleasant Conditions
the word. From this idea, he developed a color-word naming task in which he self
entitled, the Stroop Task
Since Stroop's preliminary observation, supplementary versions of the task have
been created. A number of of these studies have demonstrated that the Stroop effect can
be influenced by certain elements of priming. For example, Hinton, (1976) discovered
that prior presentation of a word whose ink color was supposed to be named on a
subsequent trial tended to reduce color naming time (as cited in Pauli et. Al, 1999).
Furthermore NeiU, (1977) further found that the presentation of an irrelevant word,
whose ink color was supposed to be named on the following trial tended to cause great
interference. Subsequent research has discovered that any kind of related word produces
interference with color naming, if its meaning is triggered by an associated word prior to
the trial (Macleod, 1991). Therefore it seems plausible that the presentation of certain
information prior to color naming will either decrease or increase response time,
depending on the relatedness of the information and the word.
Recently, with an increased interest in cognitive explanations of emotions, there
have been certain studies done regarding the Emotional Stroop Task, which have looked
at the effect of both internal and external primes on a certain task. For instance, certain
studies have shown that individuals in specific mood states (e.g. anxiety) have a harder
time performing on the Stroop task, specifically involving anxiety-related words.
Additionally, outside of the realm of emotions and mood states, it's been found that
individuals, who have been fasting, have trouble with the Stroop task specifically for
words that are related to food (Williams, Macleod and Matthews, 1996). Therefore, in
accordance with Logan's (1978) Parallel Processing Model, which states that a prime
Stroop Task in Pleasant and Unpleasant Conditions
may give a head start to numerous automatic responses activated by a color- word
stimulus, if an appropriate prime gives a particular cue to a color- word stimulus, the
reaction time is faster and if it's inappropriate, the reaction time will be slower.
Interestingly, very few studies have looked at cross modal primes and their effect
on the Stroop task, and for the most part, visual or illustrative representations have been
used for cues and prompts. However, Macleod, Matthews & Williams (1996) suggested
that, if people could characterize stimuli across modalities then there should not be any
cross-modality interference. That is, one sensory mode can elicit a response within
another. If this is true and cross modality effects can be shown, odor primes should be
able to manipulate the naming of visual or linguistic stimuli. This would prove "an
abstract, sensory- free level of representation" intervening in the Stroop task (Pauli et. al,
pg. 177 1999).
In another cross-modal Stroop study done. White and Prescott (2007) wished to
explore the cross modal cognitive associations between smell and taste. They created a
chemosensory Stroop task where participants were presented with an odorant and a
tastant and asked to identify the tastant as "sweet" or "sour" and were then subsequently
asked to press specific buttons. It was found that participants were faster at naming the
tastant when it was paired with a congruent odor, as opposed to an incongruent one.
Clearly, their results support the idea of cross modal interaction, and also illustrate the
possibility of chemosensory interference resulting from different incoming information.
Undoubtedly, smell is a very fundamental sense that has a great impact on the
memory system and retrieval processes. Because of its precise influence on the limbic
stmctures, smell has been shown to be directly connected to emotions (Macrides,
Stroop Task in Pleasant and Unpleasant Conditions
Eichenbaum and Forbes, 1982). Eich (1989) claimed that if events are encoded in a
particular state, they are most efficiently retrieved if they are in context with that initial
state. Therefore, the basic intention of this study is to determine whether priming odors
will affect performance measured by time, for color naming of visually presented words,
related or unrelated to that specific odor. More specifically, it is to determine, if odor
primes effect performance on the Stroop task for both words that are congruent to a
particular odor, or incongruent to an odor. By using both a pleasant and unpleasant
scents, the researcher wants to determine if smell can increase performance on the Stroop
task.
Method
Participants
The participants in the study were 40 undergraduate students from the University
of Western Ontario. This study was performed by way of a convenient random sample, so
there was very limited information about the dates and times that each study was
performed. They differed in sex, and ethnic backgroimd. They were all individuals
residing in the London area at the time of the study. Participation in this study was
completely voluntary. The study was conducted in the Huron University College Food
Court as well as the Huron Student Activities Centre (SAC). Due to the fact that this
study was executed on a university campus, it was assumed that a great majority of the
subjects were between the ages of 18-23.
Stroop Task in Pleasant and Unpleasant Conditions
Apparatus
Each subject was presented with one of two booklets, containing ten pages each,
where every page contained one single word written in a different color. Colors were
randomly chosen by the researcher. Thefirstbooklet contained pleasant words and then
second booklet contained unpleasant words (see Appendix A).
All willing participants were, presented with a consent form to sign. This consent
form acknowledged their anonymity, explained the purpose of the experiment, and the
approximate time it would take them to complete the task.
Half of the participants were tested in the presence of a pleasant, Calgon Vanilla
Swirl scented body mist, and half of the subjects were tested in the presence of an
unpleasant cheese smell. The specific cheese that was used was Camembert, a strongly
scented French cheese.
Procedure
Subjects were chosen by way of a convenient sample, and were required to read
and sign a consent form prior to participating in the study. Each person was either put
into a pleasant or unpleasant odor condition. Both groups consisted of 20 participants.
Pleasant Odor group. Participants were led to a secluded table in the food court or
SAC. A vanilla scented spray was sprayed five times, in the general vicinity of where the
study took place, and participants were then presented with either a booklet containing
ten unpleasant words or ten pleasant words, where words were presented in contrasting
Stroop Task in Pleasant and Unpleasant Conditions
colors. Participants were told to name the color that the ink was written in as quickly as
they could. When they were finished, the subjects were thanked for their participation and
were given a debriefing form explaining the general intentions of the study.
Unpleasant Odor group. Participants were led to a secluded area in the SAC. A
block of Camembert cheese was placed discreetly on the specific table that they were
tested on. Participants were then presented with a booklet containing either ten
unpleasant words or ten pleasant words, where words were presented in alternating
colors. Participants were told to name the color that the ink was written in as fast and
efficiently as they could. Once they had completed the task, participants were thanked for
their participation and were given a debriefing form explaining the general intentions of
the study.
After all 40 participants were tested and theirfinaltimes had been recorded, the
researcher completed a two by two ANOVA experimental design, and the data was
analyzed.
Results
A 2x2 between subjects ANOVA was completed to examine the interaction and
main effects of odor prime and word type on the Stroop task. Cell means are presented in
Figure 1 and a summarv table can be found in Appendix B.
67
15
14
13
12
11
10
9
E
8
7H
•Pleasant Word
-Unpleasant Word
6
5
4
3
2
1
0 I
Pleasant Odor
Unpleasant Odor
Figure 1. Cell means for pleasant and unpleasant odor conditions and pleasant and unpleasant
word type
Stroop Task in Pleasant and Unpleasant Conditions
A visual examination of Figure 1 reveals that there is no considerable interaction
between odor prime and word type, and the results are insignificant. Odor prime appears
to have a little effect on word type, for both words that are pleasant and unpleasant.
Although there is a slight difference between odor prime and word type in the pleasant
smelling- unpleasant word condition, the difference was not great enough to be
considered significant.
The test of the main effect of odor prime showed that the mean performance score
of the pleasant odor (vanilla) condition (M= 13.1) did not differ significantly from the
unpleasant odor (cheese) condition (M= 13.4) (F (1,36) = 0.00, n.s.).
The test of the main effect of word type showed that the mean performance of
pleasant words (M= 13.7) did not differ significantly from the unpleasant words (M=
12.8) (F 1,36) = 0.00 n.s).
The test of the interaction effect was also found to be insignificant (F 1,36) =
0.00, n.s). Raw scores can be found in Appendix C.
Discussion
It was hypothesized that certain odor primes would affect Stroop task
performance for both words that are pleasant and unpleasant in nature. The results of this
study however do not support this hypothesis. Non- significant main effects were found,
demonstrating that color-naming performance overall was not affected by the background
Stroop Task in Pleasant and Unpleasant Conditions
odor or the specific word types. As well, a non-significant interaction effect was found,
indicating that background odors did not differentially affect color- naming words
describing pleasant or unpleasant odors. Participants' performance in each condition did
not differ significantly, as they demonstrated similar times for completing the Stroop
task. These results disconfirm the notion that cross modal priming occurs, specifically for
smells and word classification.
Thefindingsof this study, specifically that, cross modal priming between
olfaction and vision proved unsuccessful is very interesting. Currently, there is not an
abimdance of literature regarding this topic, but generally cross modal priming has been
shown specifically by using the Stroop task. Macleod (1996) showed that the Emotional
Stroop Task proved to be very effective in eliciting specific mood states that either
increase or decrease performance on the task. It seems reasonable to suggest that the
specific odors used in the present experiment did elicit certain mood states, as most
participants in the unpleasant odor condition (cheese) were very effected by the smell and
responded similarly by sticking their tongues out or making a vulgar sound, and
participants in the pleasant odor condition (vanilla) responded similarly in welcoming the
scent by making a continuous effort to inhale it. However, although in previous tasks, the
extracted mood state truly effected overall task performance, perhaps in this study,
participants were not surrounded by the odor long enough to truly make a lasting impact
on their mood, thus leaving performance unaffected. It may be that the odors created an
initial reaction or preliminary feeling towards the specific scent primarily, but were not
strong enough in making a lasting mood impact where performance would be affected.
Similarly, Williams (1996) tried to explain the effects of emotions on the color naming of
70
Stroop Task in Pleasant and Unpleasant Conditions
71
emotional words by claiming that the most effective way to cause interference in naming
the colors of specific words is by increasing the resting activation of certain input stimuli
for that particular word. Emotions or feelings can enhance the activation of these stimuli.
Therefore an odor that elicits a particular emotion might increase the resting activation
level of input stimuli for words describing that odor, and therefore might slow the rate of
color naming for those words. In the present study, this was not the case, and certain
odors did not enhance the activation level of the input stimuli, and did not significantly
affect performance on the task. Perhaps it was because the words that were used in the
present study, did not adjectively describe the pleasantness (lovely) or unpleasantness
(disgusting) of a particular odor, but rather were concrete emotional words that either
described appealing (cinnamon) or unappealing (feces) items. It may be that cross modal
priming is only possible for adjectives that specifically describe the particular odor, and
not a general item.
The parallel process model, specifically the one noted by Logan (1980) proved
that a prime will generally increase or decrease performance on a certain task, depending
on whether the prime is appropriate or inappropriate. It was then suggested that priming
effects do not only occur within a single modality, but rather cross modality priming is
very effective and significant. However, the results of the current study show that in order
for cross modality priming to be exerted, very precise and particular measures needs to be
taken. In the study conducted by Pauli, Bourne, Diekmann and Birbaumer (1999), many
preliminary trials took place where participants rated odor intensities and pleasantness on
a 6-point rating scale. As well, before the initial study, participants received olfactory
stimulation by systematically inhaling odors through a specific chin-holding device.
Stroop Task in Pleasant and Unpleasant Conditions
which ensured proper sniffing. Finally, participants evaluated adjectives relevant to the
particular odors that were being used in two additional preliminary trials. Clearly, quite
extreme measures were taken to ensure the reliability of the study specifically that cross
modal priming between olfaction and vision was possible. However, perhaps cross
modality priming is only effective under very controlled circumstances and the notion of
a modality free representational system is only true some of the time. It is not to say that
different forms of sensory information cannot interact at an abstract level, but perhaps
only when the sensory stimuli are strong enough to network together.
Schmidt and Beauchamp (1988) conducted a study to determine adult-like odor
preferences and aversions in three year old children and adults. A forced- choice game
was used to try and determine hedonic reactions to nine different odorants. It was
revealed that children and adults differed in their ratings of certain odors, and response
patterns indicated that children might be more sensitive than adults to particular odors.
Although, only undergraduate students were used for the present study, the results of the
previous study are very insightful and relevant to the current findings. It may be that
certain individuals have different odor preferences and £tre either more or lese sensitive to
a certain odor. For many, the scent of Camembert Cheese was a novel smell, one in
which was extremely potent. It might have been that some of the participants were
unaffected by the powerful smell of the cheese, because of a natural liking to the stench
or for some, because of a prior interaction with it. Some participants, although might have
enjoyed the scent of vanilla, were not greatly affected by it. Therefore, it appears that not
only is the strength of the odor important to yield reliable results, but the specific types of
odors used are essential in truly affecting mood state and performance on the Stroop task.
Stroop Task in Pleasant and Unpleasant Conditions
73
Another alternative explanation of the capriciousness of the present study deals
with the way in which the task was finally presented. Participants were generally tested in
distracting, large, and unventilated areas. Although, many could smell the odor, there
were other confounding smells around them which might have affected the intensity of
the smell. As this study did not use the particular measures of diffusing odors through a
proper, mechanical device, it was difficult to control how much of the odor was actually
inhaled. As well, the actual Stroop task was given in the form of a stapled booklet rather
than on a single Stroop card. Page turning became an issue that ultimately could have
affected the results, because some participants either had trouble turning the pages, or
pages stuck together.
The existence of color and odor correspondence, is another interesting confound
that should be discussed. Gilbert, Martin and Kemp (1996), confirmed that different
odors are associated with certain colors. Therefore, the odors and the colors used in the
present experiment might have elicited an association in some cases and not others. As
well, color blindness was not controlled for and certain participants might have had a
harder time naming the colors than other participants.
For further studies, greater measures should be taken to prove the current
hypothesis. Firstly, preliminary trials should take place prior to the testing phase for
olfactory stimulation and Stroop card evaluation. As well, a greater sample of participants
should be looked at, and should be tested under very controlled conditions, including
being tested with a proper odor diffusing device to ensure and control for sufficient
Stroop Task in Pleasant and Unpleasant Conditions
74
olfactory inhalation, as well participants should be tested in a quiet and ventilated room to
control for confounding distractions both olfactory and visually. Finally, words chosen
for the Stroop task should be adjective words describing states of unpleasantness or
pleasantness as opposed to words that describe a pleasant item or an impleasant item As
well, the Stroop task should be administered on single card, and not in a booklet form, to
control for page turning problems.
If further studies regarding the issue of cross modal priming are found to be
significant, specifically for olfaction and vision, they can have many important
implications in today's modem world. Finding out which study methods are the most
efficient have always been at the forefi-ont of educational initiatives. If cross- modality
priming is possible, it can be very useful to students' particular study methods, and may
enhance academic performance. If modalities interact abstractly at a sensory-firee level,
specifically olfaction and vision, certain odors might help to enhance memory and focus.
As well, if this was tme for auditory and vision, certain kinds of music or auditory
stimulation can serve to increase focus and studying. Additionally, advertising executives
might benefit greatlyfi-omthis idea. If positive images or specific company
advertisements are shown in the presence of a pleasant odor, customers might be more
intrigued to that specific product and might decide to purchase it. Conversely, if certain
advertisements are presented in the presence of unpleasant smells, customers might be
completely turned off regardless of the greatness of the product. Therefore, advertisers
would greatly benefit by understanding the effects of cross-modal priming.
Although the hypothesis of the present study was found to be insignificant, it is
assumed that with further testing, and changes to the proposed methods of testing, like
Stroop Task in Pleasant and Unpleasant Conditions
proper control of testing conditions and sample, a significant interaction may be
determined.
75
Stroop Task in Pleasant and Unpleasant Conditions
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