Influence
of Flavor 1
Running
head: THE INFLUENCE OF FLAVOR PALATABILITY
The Influence of
Flavor Palatability on a Variable Ratio Schedule
Jillian Korn
St. Bonaventure University
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of Flavor 2
Abstract
Mazur,
1994 observed that flavored water can reinforce a specific behavior such as bar
pressing or running. The present experiment looks at flavor
palatability and its influence on bar pressing and asking can a preferred flavor
increase the instrumental behavior of bar pressing and have a subsequent
maximizing effect on a VR schedule. It
is predicted that the establishment of a flavor preference (saccharin) would
have an effect on a rat’s bar pressing behavior; increasing the rate of
response which would be reflective in the inter-response times, post
reinforcement pauses and amount of trials. The
subject’s rate of response was observed and recorded based on a predetermined
schedule of reinforcement which was a randomized variable ratio schedule. The results demonstrated that the rat
bar pressed more for saccharin reinforcement than water and that that flavor
enhanced inter-response times (IRT) and
post reinforcement post reinforcement pauses (PRP) that characterize VR
schedules.
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of Flavor 3
The Influence of Flavor Palatability on a Variable Ratio
Schedule
Learning to perform a behavior to obtain a reinforcer is a
form of learning called operant conditioning (Mazur, 1994). B.F. Skinner’s (1957) work with animals has
been instrumental in understanding operant conditioning and reinforcement
concepts such as fixed and variable intervals, fixed and variable ratios,
extinction, continual reinforcement, and discrimination. One of these concepts is the variable ratio
schedule of reinforcement. This schedule
involves changing the number of bar presses required for reinforcement. If the initial ratio was 3, the next could be
5, then 2, then 7, and the variable pattern would continue to fluctuate as
such. This pattern can vary as desired
by the experimenter and is not limited to certain numbers. Variable ratio
schedules tend to produce the highest rate of responses than the other types of
reinforcement schedules. Variable ratio
schedules tend to produce the highest rate of response, in that the
reinforcement is given when an undetermined amount of bar presses occur. The
predicted pattern for a VR schedule is a pause after reinforcement (PRP) is
presented, but these are fewer and shorter than those in the fixed ratio (FR)
schedule of reinforcement. Also in the
FR schedule the PRP’s are directly connected to the more responses that are
required the longer the pause that occurs.
In a VR schedule of reinforcement the rate of response is steady and
high, where in the FR schedule the rate of response increases as the ratio
increases. Therefore this is the most
advantageous type of reinforcement to use since the response rate will increase
because the rat does not know how many times it has to replicate the behavior
to receive reinforcement.
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of Flavor 4
Studies with animals have looked at differences in flavor
palatability and flavor aversions (Forestell & LoLordo, 2003; Schnorr &
Brookshire, 1965). Two flavors often
looked at are sugar water (saccharin), which is often considered a “preference”
to most animals, and salt water (saline), which is generally considered less
preferable to animals (Capaldi, Hunter & Lyn, 1997). Animals have a tendency to choose a sweet
tasting stimulus over that of a non-sweet tasting stimulus and consume it more
quickly. Rats and other rodents have in
addition to a sweet preference an innate preference for fats and starches
(Vigorito & Sclafani, 1988). This is
evident when studying newborn pups in that when a food source rich with
calories is presented they respond immediately.
Therefore rats and other rodents typically show an ability to discern
the amount of caloric intake, which also is enforced if they form a liking for
this stimulus. Saccharin therefore will
be preferred considering saccharin has a slightly higher amount of calories than water alone. It is thought that this preference would
occur because the rats were receiving a greater amount of calories and
therefore survive longer. This preference would occur in the thought that since they
were receiving a greater amount of calories the rat could then survive
longer.
It was shown in this study that rats prefer saccharin over
water (Manger & Graham). Given that
fact this study was interested in researching whether or not that preference would cross over to the instrumental
behavior of bar pressing. Would a rat bar press more for a preferred flavor
over water? In addition, the present
study examined whether flavor palatability (sweetness in this case) could
influence the predicated characteristic pattern of a variable ratio schedule
such that IRT would be quicker and PRP quicker with a preferred flavor relative
to a less preferred flavor (water).
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of Flavor 5
Water is typically used as a reinforcer in instrumental
conditioning. To use reinforcement such
as water or a flavor can help to reinforce a specific behavior, such as bar
pressing or running (Mazur, 1994). One
study looked at the connection between running and flavor preference; they made
the opportunity to run contingent on a flavor preference. In other words reversing the usual method of reinforcement
(Manger & Graham). Another study
found that the rat exhibited a flavor aversion towards saline as compared to
water (Cardella & Korn, 2003).
The present experiment looks at flavor palatability and its
influence on bar pressing. It has been found that rats prefer sweet flavors, and this
predisposition should influence and increase their bar pressing
behavior, and show a hedonic response to saccharin. It was hypothesized that the establishment of
a flavor preference for saccharin would have an effect on bar pressing behavior
when observed in a variable ratio schedule. It was thought that despite the “more preferred” saccharin reinforcement, both the IRT
(inter-response time) and the PRP (post-reinforcement pause) will be shortened
in length and cause each run to be quicker.
Therefore during the passage of a certain amount of time, more variable
ratio (VR) runs will be completed during the “more preferred” saccharine reinforcement
rather than the “less preferred” water reinforcement.
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Method
Subject
The subject is a female white Sprague-Dawley rat. The subject was deprived of water 24 hours
prior to the beginning of each experimental day. The animal was maintained using APA ethical
standards for the treatment and care of animals (Publication Manual of the
American Psychological Association, 2001).
Apparatus
A Skinner Box was used for reinforcement purposes. The Skinner Box contained a lever that
produced a clicking sounds when pressed down upon. A small amount of water, approximately 0.1
mL, was released when the lever was pressed down.
Procedure
A variable ratio was used and was randomly determined by
using a die and
excluded one and six.
Therefore variable ratios of two through five were used, producing the
following schedule; 5,3,2,4,2,5,4,3,5,5,2,3,4,3,4,2,5,3,2,4,2,4,5,3,5,5,2,3,4,3,2,5. The
amount of bar presses was recorded in relation to the
variable ratio schedule (IRT’s and PRP’s) using the preceding pattern for four
experimental days. The first objective
of this experiment was to establish if there was an initial flavor preference
for saccharine over water. Therefore the
rat was deprived for twenty-four hours and then presented with both flavors
(regular water and saccharin) at once to the cage for a time period of thirty
minutes. Each water bottle was weighed
before and after the thirty minute period.
This was then repeated for another day, to ensure similar results.
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The second objective of this experiment was to see if the
rat would perform a certain behavior, in this case bar pressing, more if a
preferred reinforcement was given. The
order of administration of the two flavors is as follows: regular water was
administered on days one and four and saccharine was administered on days two
and three. Reinforcement was given only
after said amount of bar presses. The
total amount of bar presses and amount of trials varied for each day. The amount of time each of these
reinforcements was given, the testing period remained the same for each day,
which was thirty minutes.
Hypothesis
H1: The rat will be able to exhibit a preference for one
flavor over the other, shown through the expediency of the bar pressing
behavior.
H0: The rat will show no preference to either of the two
flavors.
Results
Day 1. A two-bottle
preference test was conducted. The subject was left
in its cage while both water bottles were placed in the cage for 30 minutes. The subject had been deprived of water for 24
hours. Each water bottle was weighed before and after. Both of the water bottles were the same
weight in the beginning at 475 grams.
After the 30 minute period the regular water bottle weighed 471g and the
saccharin water bottle weighed 469g. The
results show that the rat drank more saccharin based
water than regular water.
Day 2. The subject
was left in its cage while both water bottles were again placed in the cage for
30 minutes. The subject had been deprived
of water for 24 hours. Each water bottle
was weighed before and after. Both of
the water bottles were the same weight in the beginning at 475g. After the 30 minute period the regular water
bottle weighed 473g and the
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of Flavor 8
saccharin
water bottle weighed 464g. The data
shows that the rat consumed more of the saccharin based water than the regular
water.
Day 3. The subject
was placed in the Skinner Box and observed for 30 minutes using only water as
the reinforcement. The mean IRT for this
day was 3.77 and the mean PRP for this day was 26.54. The subject was able to complete 33 trial
runs within the 30 minutes.
Day 4. The subject
was placed in the Skinner Box and observed for 30 minutes using only saccharin
as the reinforcement. The mean IRT for
this day was 3.58 and the mean PRP for this day was 22.90. The subject was able to complete 37 trial
runs within the 30 minute time period.
Day 5. The subject
was placed in the Skinner Box and observed for 30 minutes using only saccharin
as the reinforcement. The mean IRT for
this day was 4.12 and the mean PRP for this day was 17.72. The subject was able to complete 36 trial
runs within the 30 minutes.
Day 6. The subject
was placed in the Skinner Box and observed for 30 minutes using only water as
the reinforcement. The mean IRT for this
day was 5.60 and the mean PRP for this day was 41.59. The subject was able to complete 17 trial
runs within the 30 minutes.
Using these data further calculations were made to help
discern whether the subject showed a
preference for one of the flavors and would perform a behavior more quickly and
more often if presented with the preferred stimulus. An alpha level of .05 was used for all
statistical tests. A t-test was
preformed to determine the significance between the water and saccharin
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of Flavor 9
treatments IRT and PRP values. The mean IRT saccharin was 3.850 and the mean
IRT water was 4.685. IRT water vs IRT
saccharin t(1)= -1.295, p< 0.419 not showing a statistical
significance, but is approaching significance.
This is shown on figure 1. The
mean PRP saccharin was 20.310 and the mean PRP water was 34.065. PRP water vs PRP saccharin t(1)=
-1.360, p< 0.404 not showing a statistical significance, but is
approaching significance. This is shown
on figure 2. Lastly a t-test was
performed to determine the significance between the amounts of trials completed
for each of the two flavors. The mean
amount of runs for saccharin was 36.50 and the mean amount of runs for water
was 25.00. Runs saccharin vs. Runs water
t(1)= 1.533, p< 0.368 not showing a statistical significance,
but is approaching significance. These
results are shown on Figure 3.
Discussion
The present study looked at the preference between two
flavors and attempted to determine if the rat would increase its bar pressing
rate due to the presence of the preferred stimulus (flavor). It was based on numerous studies (Capaldi,
Hunter & Lyn, 1997; Mazur, 1994) that had examined preferences or aversions
of rata. Different types of
reinforcement schedules were used in these studies, one of which was the
variable ratio schedule. In the present
experiment, a die was used to randomize the ratio pattern. The numbers one and six were not used because one would be indicative of a continual reinforcement
pattern, and would not include a PRP value.
Six was not included for the purpose of keeping the number of
ratio values even.
This
experiment shows that the rat showed a preference
towards saccharin over water. This
was exhibited within the first two days because on both days
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of Flavor 10
the rat consumed more of the saccharin based water than the
regular water. Albeit not by much, but
overall the consumption was greater.
This was also proven through the behavioral testing. When the preferred flavor was present the
rat she completed more trials, and had faster PRP and
IRT values than when water was used as the reinforcement. The PRP data demonstrated a value that was approaching a statistical difference between the
two conditions, meaning that the rat took longer breaks after being reinforced
during the water treatment. This was
thought to be indicative of a preference for the saccharin since she took less
time to resume bar pressing after being reinforced during the saccharin
condition. It was
thought that by waiting longer to resume bar pressing for reinforcement, the
rat was in fact displaying a hesitance to consuming the regular water. The IRT data also showed a value that was
approaching a statistical significance between the two conditions, meaning that
it took the rat took longer during the water treatment to complete the certain
set of bar presses before being reinforced.
The variable ratio that was used helped enable the subject to obtain the
highest possible number of trials. The
amount of trials completed showed a value that was approaching a statistical
significance between the two conditions, showing that the rat was more apt to
complete more bar presses in the presence of the saccharine treatment. Since the data was significant the null
hypothesis can be rejected and therefore the alternative hypothesis can be
supported. The expediency of the bar
pressing was shown through the statistical significance shown by the IRT and
PRP values as well as the amount of trials that were completed. Based on the rat’s performance, it can be
concluded that a flavor preference was exhibited for saccharin over the regular
water and this was shown through the rat’s bar pressing behaviors. To obtain results that were statistically
significant the experiment would have to include more days to provide an
adequate demonstration of the increase in the amount of bar presses
achieved. The rat that was used could
have been ill at the time of performance due to the fact that she passed away a
week later, this could have been a reason for the lack of statistically
significant results.
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References
Capaldi, E., Hunter, M. & Lyn, S. (1997).
Conditioning with taste as the CS in conditioned flavor preference
learning. Animal Learning &
Behavior, Vol 25(4), 427-436.
Cardella, K., & Korn, J. (2003).
Effect of Flavor Preference on Bar Pressing Using a Variable Ratio
Schedule. Unpublished experiment,
St. Bonaventure University.
Forestell, C. & LoLordo, V. (2003).
Palatability shifts in taste and flavor preference conditioning. Quarterly Journal of Experimental Psychology:
Comparative & Physiological Psychology, Vol 56B(1), 140-160.
Manger, J., & Graham, D. (1994).
Can the opportunity to run serve as a reinforcer to condition a
flavor preference in rats? Retrieved
February 24, 2004, from http://pirate.shu.edu/~vigorimi/shujp/94era1.html
Mazur, J.E. (1994). Learning and Behavior (3rd ed.)
New Jersey: Prentice Hall.
Publication Manual of the American Psychological
Association. (2001, 5th ed). Washington, D.C: APA Press.
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of Flavor 12
Schnorr, J. & Brookshire, K. (1964).
Distilled water and tap water as factors in taste preference
experimentation. Psychological
Reports, 17(1), 191-194.
Skinner, B.F.
(1957). Schedules of
reinforcement. Acton, MA; Copley
Publishing Group.
Vigorito, M. & Sclafani, A. (1988). Ontogony of
polycose and sucrose appetite in neonatal rats. Developmental Psychobiology,
21, 457-465.
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of Flavor 13
Table 1: Statistical Analysis of IRT and PRP during Sugar
and Water Treatments as well as Amount of Trials Completed
Paired samples t test on IRTSAC vs IRTWAT with 2 cases
Mean IRTSAC =
3.850
Mean IRTWAT =
4.685
t = -1.295
df = 1
p = 0.419
Paired samples t test on PRPSAC vs PRPWAT with 2 cases
Mean PRPSAC =
20.310
Mean PRPWAT = 34.065
t = -1.360
df = 1
p = 0.404
Paired samples t test on RUNSSAC vs RUNSWAT with 2 cases
Mean RUNSSAC =
36.500
Mean RUNSWAT =
25.000
t = 1.53
df = 1
p = 0.368
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Figure 1: Mean IRT values for saccharin and water
treatments.
Figure 2: Mean PRP values for saccharin and water
treatments.
Figure 3: Mean amount of trials completed for saccharin
and water treatments.
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Days 1-4 (Days 1 and 4= water and Days 2
and 3= saccharin)
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Days 1-4
(Days 1 and 4= water and Days 2 and 3= saccharin)
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of Flavor 17
Days 1-4
(Days 1 and 4= water and Days 2 and 3= saccharin)
