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Introduction
Feelings of hunger, a natural human instinct, are controlled by various physical
and psychological functions. But the interaction of these functions to create hunger and
the priority given to certain functions over others in reaction to stimuli present an
important subject of study. This study benefits multiple fields, including the
understanding of eating disorders and the advancement of the food industry (Marcelino et
al., 2001). It also comes in handy when faced with the dilemma of whether or not to eat
an appetizing piece of chocolate cake even though you’re not hungry. We chose to study
the psychological force of a visual food stimulus and its effects on the individual’s
feelings of hunger. Past studies have supported the supposition that “the sight and a brief
taste of a food actually ‘primed’ the appetite, regardless of energy state” (Lambert et al.,
1991). The visual stimulus also appears to have a stronger influence on hunger than other
types of stimulus, “for example, visual food cues such as the sight of a plate of lasagna
might be more powerful than olfactory cues such as the smell of lasagna” (Lambert et al.,
1991). These external stimuli seem to take precedence over the actual physical state of
being hungry or full. “Cornell et al. (1989) showed that the sight of food enhanced
reported desire to eat it, even when subjects were satiated and this was confirmed by the
quantity eaten in further ad libitum consumption” (Marcelino et al., 2001). Based on
these observations and previous studies, we hypothesize that feelings of hunger can be
manipulated as a psychological phenomenon by the introduction of a visual stimulus. In
order to examine this subject, our study includes a two-part survey one of which includes
a visual food stimulus to provide a comparison between the two situations.
Methods
All participants in the experiment were Dr. McKeachie’s honors psychology 114
students. For the initial survey given, there were twenty participants. Eleven of the
subjects were female and nine were males. Eleven of the students had eaten prior to
answering the survey and nine had not eaten beforehand. For the second survey given,
there were a total of five participants. All participants were from Dr. McKeachie’s
honors psychology 114 class as in the initial survey. Of the five students, four were
female and one was a male. Two students had not eaten beforehand and three had eaten
food prior to coming to class.
A food stimulus (donut holes) was absent in the initial survey and nearby for the
second. We used the food as an independent variable to test for level of hunger indicated
by students when presented with just a survey and with a survey in the presence of the
food stimulus. Fort the initial survey, the students specified their hunger levels at the
beginning of the class by rating it on a scale of 1-5 with 1 signifying the most hunger.
Students were also asked if they had eaten before class and how hungry they thought they
would be at the completion of the class. When presented with a food stimulus, the
students answered the same questions as in the first survey where no stimulus was
present. But the students also rated their desire to eat the food on the table and their
personal like or dislike for the donut holes.
The two surveys were given at the beginning of classes. The first survey without
the food stimulus was given during the beginning of a 1.5 hour lecture at 10:30AM. The
second survey was given during a subsequent discussion section at 10:15AM. All
students received the same survey regardless of their age, gender, or whether they had
eaten or not. The students were simply told to fill out the survey honesty and quickly
based on their current hunger and eating habits prior to the class. When presented with
the food stimulus, the students were allowed to view the donuts for a minute before
answering the survey questions.
Results
(Still to be done when all numbers are in once second survey is passed out Monday)
Disscussion
There were some unforeseen factors in our experimental procedure that made it difficult
to garner accurate results the first time we attempted the second part of our experiment.
That part included introduction of the subject pool to the food stimulus. We did not
account for not having regular class on Monday and therefore found it difficult to gather
everybody together for the second part of the survey and the exposure to the food
stimulus. The time difference between the first and the second survey also was a control
that we originally expected to have and did not have. Another unforeseen factor was the
occurrence of Passover which made it impossible for many people who wanted to eat the
doughnuts we presented because they were not kosher for Passover. We were able to
remedy these problems however because of our ability to give out the second survey
during the following Monday class, thereby eliminating the time difference of the first
and second survey as well as lifting the food restrictions placed on some by Passover.
If one would want to continue or expand upon our research there would be a
number of ways in which to do so. They could of course gather a larger subject pool to
perform the experiment on thereby gathering more accurate results. A control group
could be instituted in which no exposure at all to a food stimulus would occur, thus
allowing the researchers to compare a person without any exposure to food stimulus to
those who were not exposed and then exposed at a later time to the food. Gender
differences could be measured as well. Even though we took an interest in the issue of
gender in summarizing our results, a whole study could be conducted with that one topic
at hand. Furthermore, the actual measuring of physiological symptoms of hunger could
be useful in determining the actual levels people were at hunger-wise instead of relying
on a self report which could at times be biased.
We found a number of studies that studied a similar problem to ours, that being if
mental manipulation through exposure to a food stimulus could affect physiological
hunger in a person. One such study was done on the issue of craving in which craving is
defined as “a subjective motivational state analogous to emotions rooted in the idea that
cues indicate a state of need”. In other words, craving is the emotional feeling of wanting
something determined by certain physiological and mental cues. Craving and hunger are
similar in that both reflect the need to ingest something. In this study, subjects were
asked to measure their level of craving for a number of things, including food, drugs, and
cigarettes. From these self-reports it was determined that there are two types of craving,
background craving which is a steady state of wanting something throughout the day and
requires no environmental stimuli, and Episodic craving in which there are occasional
bouts of intense craving triggered by environmental stimuli or affective cues. Our
experiment dealt with episodic craving as we introduced an environmental stimuli
(doughnuts) to people that had not been craving a doughnut beforehand, thereby initiating
their craving. Frequent episodic craving in general tends to be a precursor to relapse,
meaning either going off a diet or having a cigarette, as it is often too hard to resist.
Another interesting study was “Self-Reported Measures of Appetite in Relation to
Verbal Cues About Many Foods” done by Michael E. Oakes and Carole S. Slotterback.
In this study both men and women college students were exposed to a list of written food
cues and asked to rate each of the foods according to their nutritional value. Subjects
exposed to the food lists reported increases in hunger, desire to eat, and number of foods
currently hungry for as opposed to the controls who did not report any such feelings of
reduced fullness. This study thereby concluded that exposure to food cues increased
apparent desire of food. The study also took into consideration the gender differences,
and surprisingly concluded that there were no main effects involving gender on the level
of hunger after exposure to food cues. This study used both real foods and cognitive
expression as cues. It was found that both cognitive cues and real foods increased reports
of general appetite. It was also concluded that external food cues, no matter what they
may be, increase the hunger of both dieters and those that are not watching their weight,
however those exposed to the cues, especially women, reported cravings for lower fat
foods more often than higher fat ones after the experiment was conducted. This funny
fact reflects greatly the culture of our society in which eating and desire for food is
somewhat looked down upon and thereby remedied by reporting a desire for healthier
foods.
A last study looked at was “Determinants of Eating Initiation” in which it was
determined that interviewing people at times more or less distant from meals is an
effective way to obtain various levels of subjective hunger. This experiment was almost
identical to our own. Subjects were exposed to a food stimulus, pizza, and then asked to
self report on their hunger levels. It was concluded that hunger has no significant effect
on the influence of pre exposure to food stimuli, thereby supporting our results that we
can manipulate hunger levels through food cues. An interesting point in this study was
concerning gender differences. It seems that when women are not hungry, they rate their
appetite for pizza lower than males however when they are hungry, women tend to rate
their appetite just as strong as males do. The study also showed that actually seeing the
food, visual pre exposure, had more of an effect on females than males when measuring
increase in appetite yet after exposure to the food there is no gender difference in
appetite.
The previous study as well as the others examined all supported our hypothesis
that we can mentally manipulate people’s hunger through exposure to a food stimulus. It
is also interesting to note that eating motivation, although influenced by the internal
emotional state of seeing the food, is also contingent upon the level of hunger the person
had before exposure to the food. In other words, if someone is completely full there is
very little evidence to suggest that putting their favorite food in front of them will make
them eat. All in all our experiment and results seemed to coincide favorable with the
other studies done on this topic. More research could definitely be generated in this area
in help for curing cravings of both food and drugs as well as in curing problems like
obesity and obsessive compulsive eating.
Citation
Lambert K.G., Neal T., Noyes J., Parker C., & Worrel P. (1991). Food-related
stimuli increase desire to eat in hungry and satiated human sujects. "Current
Psychology" 10, 297-303.
Marcelino A.S., Adam A.S., Couronne T., Koster E.P., & Sieffermann J.M. (2001).
Internal and external determinants of eating initiations in humans. "Appetite" 36, 9-14.