The Effect of Color on Flavor Perception

This topic submitted by Joseph Puchala, Amy Humphrey, Laura Runyan, and Travis Williams on 12/8/05. [Section: Winnubst]
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Natural Systems 1 Syllabus---Western Program---Miami University



The Effect of Color on Flavor Perception
Joseph Puchala, Amy Humphrey, Laura Runyan, and Travis Williams

Abstract
Human beings depend on their five senses to alert themselves of the world and to allow interaction with the sources of the sensed inputs. However, during the transmission and integration of senses the perception of the sense can be altered. The purpose of the conducted experiment is to explore the affects of visual interference with the perception of taste. Subjects in this experiment were given vanilla flavored yogurt colored either plain, red, or blue to determine if the visual cues affected the interpretation of taste. This experiment also investigated whether or not previous color and taste preferences affect signal interpretation and if gender and age also have a role.

Introduction

Taste in humans is facilitated by modified epithelial cells organized into taste buds, located in areas of the tongue and mouth. There are five scientifically recognized taste perceptions – sweet, salty, sour, bitter, and umami (Japanese for “delicious”) – which when combined in different ratios create the diversity of flavor present in today’s world. Transduction, the transformation of stimulus energy into a change in the membrane potential of a sensory receptor, in taste cells works by chemoreceptors detecting changing gradients of certain substances. For example, a taste bud that detects saltiness has channels for Na+ to diffuse across and depolarize the cell causing signal transmission (Campbell 1055).
There is a strong correlation between tastes and color. In fact, “Flavor perception arises from the central integration of peripherally distinct sensory inputs (taste, smell, texture, temperature, sight, and even sound of foods)” (Small). “One of the best examples of such an integrative process may be flavor perception, whereby activation in two peripherally distinct neural systems, olfaction and gustation, combines to give rise to a unified oral sensation” (Dalton), thus proving that flavor perception begins in the brain. Different manufacturers often make the flavors the same colors for different foods because that is what the mass majority of people recognize them as; for instance cherry is red, lemon or banana is yellow, peach is a light orange, etc. This study, which is to take place on the main campus of Miami University Oxford, is to figure out how strong the tie between color and taste is, using yogurt, by giving subjects a yogurt that has a flavor which doesn't correspond with its color. Our hypothesis is that the correlation will be strong enough that people will believe that the flavor of the yogurt corresponds with its color, even though it doesn't. Past research has concluded that our senses impact our memory and thus our behavior (Hughes). The initial question was, "What effect does color have on human perception of taste?" Since color and taste also correlate in nature, i.e. lemons are actually yellow and peaches are orange, it's likely that the association between flavor and the color of the yogurt will be even stronger than if it were just a societal rule that strawberry flavored foods are red. The interest in this study lies in, should our hypothesis fail to be proven incorrect, the effect one sense has on another, when it is assumed that we, as humans, experience what is perceived through only one sense, in this case taste. Figuring out whether our mind can override our senses to tell us that we taste something that we are not tasting would be an interesting aspect of human consciousness and study. How people react with their senses in an environment is of great interest to scientists; which senses hold more power over an individual's perception of the world would give interesting insight into how the brain works.

Relevance

The relevance of this project has become more prominent in modern times, although the practice of dying food has been active since as long ago as 400 BC (Downham). Dye in food has taken on a variety of meanings to consumers, from added nutrition to easy flavor recognition to an appeal for children. In the advertising and product placement market, different audiences are targeted with different types of colored food; for example, the production of green and purple ketchup for kids. Kids will ask their parents to buy the colored ketchup instead of regular ketchup even though it tastes the same and is more expensive (Begun). Because it's not red, it's “cooler.” Regular vanilla ice cream is dyed red, yellow, and blue and marketed as being "Superman Ice Cream." Yellow Little Debbie cakes with vanilla flavored frosting will sport new colors and designs during holiday seasons like Halloween, Christmas, and Valentine's Day. Do people perceive these products as tasting different? Much basic food recognition is completely related to color. If a person saw a smooth, reddish-orange soup, they would probably assume it was tomato soup for this reason. The soda industry bases many of their advertising campaigns on color. When Coca Cola came out with clear Coke a few years back, it was a large failure. Many consumers said it "wasn't as good." The only thing that had been removed was the caramel-colored dye. It is possible that simply knowing it wasn't brown like regular Coke altered the consumers' perception of the taste, and that had they taste tested the two blindfolded, they wouldn't have been able to tell the difference. People often tell their drinks apart or keep track of unlabeled stored drinks according to their color, and most of our drinks are artificially colored. It is common to assume that a yellow or green colored drink is lemon-lime or citrus flavored, and that an orange drink is orange flavored. Would a coke-flavored drink that was orange disgust people? Would they believe that they perceived some orange flavor in the drink just because of its color? This experiment is completely relevant, not only to human studies, but to a massive part of the food marketing industry.


Procedure

Vanilla yogurt was the key ingredient for this experiment. The yogurt was divided into four batches. An unchanged batch of yogurt was the control. The two other batches were made into the variables for the experiment by adding red and blue food dye to each. The yogurt was served in portions of approximately 2 tablespoons in small, unmarked paper cups. Each subject was given a clean plastic spoon to eat the yogurt. All subjects were asked of any food allergies before testing.
The study area for the experiment was the Miami University campus at Oxford, OH. Testing was done more specifically within the Harrison Dining Hall lobby, a heavily trafficked area. The lab set-up involved a table with yogurt manned by three to four researchers who passed out yogurt and questioned subjects. Around fifty subjects were tested for each variable and control. All the researchers worked to bring possible subjects over to the table.
A subject that wished to take part in the test would come over to the table. First the researchers would ask about food allergies. Next a researcher would hand him or her a yogurt sample and a questionnaire. After the subject had eaten the sample, the subject will write what flavor he or she believed the sample to be on the questionnaire. The questionnaire also will ask age, sex, favorite flavor, and favorite color. Data collected was sorted into three different categories. The first category is subjects who guessed the flavor correctly despite misleading visual cues. The next category is subjects who guessed a flavor that matches the color of the visual cue (strawberry flavor would be an example for the color red). The third category is subjects who guessed the flavor incorrectly and guess a flavor that is not related to the visual cue provided by the food dye. Data for this project was analyzed by using a statistical test called a chi-square test to test if the differences in distribution are significant.
This experiment required a large number of subjects. However, the Natural Systems I class could not volunteer to help because this experiment required that the subjects be blind to the procedure. To compensate for the need of many subjects the researchers tested on three separate days in a period of three weeks.

Results

This experiment produced data that revealed a trend supporting our hypothesis that color affects flavor perception. The percent of people incorrectly guessing a color-related flavor significantly increased with the introduction of food dye. The results for the second variable, blue-green dye, are skewed, however, due to over-experimentation. The experiment was performed in the same location every time to try to prevent creating more variables (such as a location variable), but this resulted in repeat participants that eventually figured out that the food was dyed. However, many still guessed color related flavors. Flavor preference seemed to have some affect on the results. Sixty-six percent of people who listed vanilla as their favorite flavor guessed it correctly, but only thirty-three percent of people with other favorite flavors guessed it correctly. Chi-Square Tests for significant correlation produced a chi-square value of 62.51 and a p-value of less than or equal to 0.001. This means that there is a significant correlation of food color to human flavor perception. However, the ANOVA tests to check for influences of factors like age and gender on flavor perception produced p-values of .387 and .435 which indicate that age and gender have no effect on flavor perception. Graphs and pie charts of the data are presented on page nine.

Discussion
This study has many fascinating implications. How people perceive the world is an important aspect of study. Our results most obviously show that sight has a great deal to do with how people, or at least young adults, perceive taste. The data may be skewed, however, because not only did most people realize we were testing them, but we also had a few repeat participants. Even with the control group, though, we had more people guess a wrong flavor than a correct one. This is most likely because most people assumed we were trying to trick them. The results from the red dye trial are the most accurate, mostly because we had less repeat participants than on the blue dye day, and also because people were less apt to believe we were trying to trick them, which is evident by the overwhelming amount of people that guessed a flavor related to the color of the yogurt. The red trial also was the only trial where more people whose favorite flavor of yogurt is vanilla guessed the flavor incorrectly where as the other trials those whose favorite flavor is vanilla more often than not guessed correctly.
One aspect of our results which is important to consider is that yogurt itself has a taste, so the participants are tasting vanilla flavored yogurt, and not just vanilla. Some of the wrong guesses may be attributed to this fact, but for the most part yogurt eaters know what yogurt tastes like (especially those whose favorite flavor is vanilla). However, even they perceived a different flavor than what it actually was. It may be pertinent, then, to recreate this experiment using a different food, with a more recognizable individual taste, that can still be dyed. It could have also made a difference that the yogurt was fat free, especially to those who had had vanilla yogurt before. The large amount of participants (at least 50 at each trial), however, suggests that our data is due more to participants perceiving the flavor as different from what it actually was because of the misleading visual cues, especially since our p-value is less than .05, and so we reject the null hypothesis.
As Small and Campbell both point out, flavor perception occurs in the mind. All other senses of course are processed in the brain as well. A cross between the senses, then, can be expected, so perceiving flavor as different than what it actually is is not a surprising result. How the cross occurs, however, is an important question, one that cannot be answered with this experiment.

Conclusion
Based on the project as a whole, we were able to obtain substantial evidence that supported our hypothesis. However, the results were slightly skewed due to a matter of location. Because we had repeat participants, their memory of previous testing allowed them to guess correctly. Had we experimented at other locations around campus, most likely our results from the final variable would be more useful. Unfortunately, we would also have to test the yogurt as a control, as well as the other colors, at these new locations, which most certainly would have resulted in similar data. Despite this shortcoming, the data was still conclusive; sight does affect taste in a big way. The testing of the first variable showed that well.
This experiment contains important scientific aspects. The fact that we relate color with nature implies that we rely on our natural surroundings as a basis for man made goods. The colors that manufacturers use to sell their products are based on how the consumer interprets them, and in turn the consumers recognize these colors from a familiarity with nature. The power of sense is something humankind takes for granted every day. If we could not rely on our senses, how would we be able to recognize anything at all?





Bibliography

1. Christianson, John. “Effect of Low Body Temperature on Associative Interference in Conditioned Taste Aversion.” Perceptual & Motor Skills, Vol. 100, Issue 3, June 2005 p913-919. Academic Search Premier. EBSCOhost. Miami University Library, OH. 10/4/05. http://www.epnet.com/.

2. Cook, David. “Correlating instrumental measurements of texture and flavour release with human perception.” International Journal of Food Science & Technology, Vol. 40, Issue 6, June 2005, p631-641. Academic Search Premier. EBSCOhost. Miami University Library, OH. 10/4/05. http://www.epnet.com/.

3. Begun, Bret. “Open Up and Say 'Blaaaahhh.” Newsweek, Vol. 137, Issue 16, 04/16/2001, p10. Academic Search Premier. EBSCOhost. Miami University Library, OH. 10/4/05. http://www.epnet.com/.

4. Downham, Alison. “Colouring our foods in the last and next millennium.” International Journal of Food Science & Technology. Vol. 35, Issue 1, Feb. 2000, p5-22. Academic Search Premier. EBSCOhost. Miami University Library, OH. 10/4/05. http://www.epnet.com/.

5. Schubö, Anna. “Perceiving while acting: action affects perception.” Psychological Research. Vol. 68, Issue 4, Aug. 2004, p208-215. Academic Search Premier. EBSCOhost. Miami University Library, OH. 10/4/05. http://www.epnet.com/.

6. Stahl, Jutta. “Accessory stimulation in the time course of visuomotor information
processing: Stimulus intensity effects on reaction time and response force.” Acta Psychologica. Sep. 2005, Vol. Academic Search Premier. EBSCOhost. Miami University Library, OH. 10/4/05. http://www.epnet.com/.

7. Mulligan, Neil W. “The effects of perceptual interference at encoding on organization and order.” Journal of Experimental Psychology / Learning, Memory & Cognition. Vol. 25, Issue 1, Jan. 1999, p54. Academic Search Premier. EBSCOhost. Miami University Library, OH. 10/4/05. http://www.epnet.com/.

8. Stins, John. “The Multi-Source Interference Task: The Effect of Randomization.” Journal of Clinical & Experimental Neuropsychology. Vol. 27, Issue 6, Aug. 2005, p711-717. Academic Search Premier. EBSCOhost. Miami University Library, OH. 10/4/05. http://www.epnet.com/.

9. Hughes, Robert. “The Impact of Order Incongruence Between a Task-Irrelevant Auditory Sequence and a Task-Relevant Visual Sequence.” Journal of Experimental Psychology / Human Perception & Performance. Vol. 31, Issue 2, Apr. 2005, p316-327. Academic Search Premier. EBSCOhost. Miami University Library, OH. 10/4/05. http://www.epnet.com/.


10. Small, Dana M. “Experience-dependent neural integration of taste and smell in the human brain.” Journal of Neurophysiology. Vol. 92, Issue 3, Sep. 2004, p1892-903. Academic Search Premier. EBSCOhost. Miami University Library, OH. 10/4/05. http://www.epnet.com/.

11. Buettner, Andrea1. “Physiological and analytical studies on flavor perception dynamics as induced by the eating and swallowing process.” Food Quality & Preference. Vol. 13, Issue 7/8, Oct. 2002, p497. Academic Search Premier. EBSCOhost. Miami University Library, OH. 10/4/05. http://www.epnet.com/.

12. Dalton, P. “The merging of the senses: integration of subthreshold taste and smell.” Nature Neuroscience. Vol. 3, Issue 5, May 2000, p431. Academic Search Premier. EBSCOhost. Miami University Library, OH. 10/4/05. http://www.epnet.com/

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