Transcript Slide 1

Do Rats Have the Ability to Discriminate Between Words?
Sarah R. Heckendorn and Christina M. Scheele
Randolph College
Founded as Randolph-Macon Woman’s College in 1891
Lynchburg, VA 24503
Introduction
Average Latency to Dig
(Seconds)
Discrimination is the ability to learn when a stimulus is given a reward
can be retrieved (Chance 2006). Studies have showns rats ability to discriminate
between tones and no tone in a T-maze (Eninger, 1951) and between two
different sounds, such as White noise and FM radio (Sakai & Kudoh, 2005).
However there have been few studies done to find whether rats can
discriminate between human words. Will the sounds of the two words left and
right alone be enough for rats to learn to discriminate to get a reward? This
knowledge could aid in our increasing knowledge of animal intelligence and their
ability to understand language.
Results
Figure 1
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Rat 1 (Lexi)
Rat 2 (Jacques)
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Method
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Discussion
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Trial Day
• While other researchers (Eninger, 1951; Sakai & Kudoh 2005) have found
the possibility for rats to be able to discriminated between different tones,
in this present experiment there was no conclusive evidence that supports
the conclusion rats able to discriminate between two words: left and right.
Preference index scores do show slight learning did occurred. This is
indicated by the positive scores, however the correct cup choice was never
above chance for either rat.
Subjects
The subjects were adult, male Long-Evans rats (N=2). Rats were on food
deprivation during the length of the experiment but given water freely.
The T-Maze was used with a small plastic cup at the end of each choice arm. The
plastic cups contained crushed Froot Loops, with the specific reinforced cup
(switched randomly) having six half Froot Loop pieces.
Procedure
Each Rat was allowed to explore the T-maze for five minutes with 25 half Froot
Loops scattered throughout the maze and in the cups during the shaping phase
of the experiment. During both shaping and training, instrumental music was
played in the background to drown out extraneous noise. Training was then done
for five consecutive days; each training day consisted of 20 trials with left and
right cup reinforcement switching randomly. The correct reinforcement location,
left or right, determined which direction the experimenter would say to the rats.
Verbal cues were repeated until the rat made a cup choice (placed it’s head in the
plastic cup). If the cup choice was correct the rats were allowed to eat three Froot
Loop pieces and then were removed from the maze. If the cup choice was
incorrect the rats were allowed to see that the cup was empty and then taken out
of the maze. The latency to choose was timed from the first word spoken to the
time the rat put its head in the cup to find the Froot Loops. During the test
section of the experiment, direction was chosen at random and was continuously
verbally given to the rat for two minutes. The amount of time spent in each arm
was recorded and a preference index was calculated.
Figure 2
Correct Cup Choice Average (0 =
Incorrect Choice, 1 = Correct
Choice)
Apparatus
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Rat 1 (Lexi)
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Rat 2 (Jacques)
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0.1
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There was no statistical significant difference in latency to choose a cup
choice between the first trial (M=7.49, SD= 7.28) and the last trial
(M=8.25, SD= 15.20) for rat 1, t(19)=-0.189, p=0.852. In contrast there
was a statistically significant difference between the first latency (M=11.34,
SD= 15.95) and last trial’s latency (M=2.94, SD= 1.99) to choose times for
rat 2, t(19)=2.311, p=0.032. There was no statistically significant difference
between correct cup choice between the first and last day of training for
either rat t(19)=0.00, p=1.00, t(19)=-0.52, p=0.61, respectively. The
preference index for Rat 1 was 0.15 and was 0.08 for rat 2.
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Trial Day
References
Chance, P. (2006). Learning and behavior: Active learning edition
(5th ed.). Belmont, CA: Thomson Wadsworth.
Eninger, M. U. (1951). The rate of learning a tone-notone discrimination as a function of the duration at
the time of the choice point response. Journal of
Experimental Psychology, 41(6). 440-445.
Sakai M., & Kudoh, M. (2005). Characteristics of sound
discrimination enhancement after sound exposure
in adult rats. Behavioral Neuroscience 119(4). 961-973.
• The one statically significant result, latency to dig between first trial and
the last trial for rat 2, could be due to an accidental variation in experiment.
Although this variation was completely accidental, there were also other
slight variations between and with-in subjects that could have impacted
results.
• The previous handling methods of the rats could be a possible confound.
Rat 1, who has been handled by the experimenter giving the cues more,
could be adjusted to the experiment methods, while the method used by the
experimenter who handled rat 2 was completely different. Rat 1 could have
been more comfortable starting the experiment than rat 2, for whom this
experimenter’s voice was novel.
• Other possible confounds include extraneous noise not reduced by the
instrumental music and human error, in intonation and in exhaustion, could
have negatively affected the results.
• Researchers suggest that if this experiment was to be repeated, a
recording of someone saying left or right should be used, or the use of
other words, as well as more training days. Also a noncontingent
reinforcement plan should be used, where the rat is allowed to examine
both cups even if he goes to the incorrect cup first.