Single reward vs. two different rewards:

1
Single reward vs. two different rewards Are
two different rewards preferred over one
consistent reward in odor discrimination by
rats? Anu Thapa Randolph College Lynchburg, VA
24503
Introduction According to operant conditioning,
theory, reinforcers work while they are provided
consistently. The contiguity as well as
contingency of the reinforcers with the behavior
affects how quickly a behavior is learnt or lost
(Chance, 2005). Much research has been conducted
to examine these effects on operant
conditioning. However, there is not much
literature available that examines the effect of
using two different kinds of rewards to reinforce
the same behavior. . This experiments examines
the effectiveness of using two different rewards
to reinforce a behavior to that of using a
consistent reward to reinforce the same behavior.
I hypothesized that there would be a difference
between the effectiveness of using one reward
over two different rewards in odor discrimination
for rats.
Figure 1
Results Because the subject for this experiment
was a single rat, it was not possible to run a
dependent sample t-test on the data collected.
However, the average latency to dig for the
cocoa vs. cinnamon condition was 2.58 seconds,
and that for the cumin vs. cardamom condition was
1.70 seconds. Latency to dig (sec) Cocoa vs.
Cinnamon 4.98, 3.51, 4.92, 2.20, 1.40, 1.42,
1.45, 1.48, 1.47. Cumin vs. Cardamom 1.25, 1.84,
2.49, 0.96, 1.82, 0.96, 1.54, 2.71 The results
for the testing day are unavailable because the
rat refused to dig.
Shaping (Day 1) Two cups of unscented sand (three
trials)
Shaping (Day 2) Two cups of unscented sand (six
trials)
Figure 2
Training (Day 1) Two cups of scented sand
(cocoa/ cinnamon) (ten trials) with 75 correct.

• Discussion
• The results are inconclusive because the rat did
  not dig during the crucial testing period.
• The fact that the rat took less time to dig
  during the cumin vs. cardamom condition can be
  attributed to the rats memory rather than
  preference over two different rewards.
• The latency to dig of the rat during the very
  first trial of the cumin/cardamom condition shows
  that the speed was due to memory.
• For future purposes it would be prudent to use
  more than one rat as subject.

Method Subjects A hundred and twenty-days old,
male Long-Evans rat (N1) was reduced to and
maintained at 85 of his free-feeding weights one
week prior to and during experimentation. Water
was available ad libitum. Apparatus All shaping,
training, and testing took place in the rats
home cages. Plastic Nalgene cups (125 ml size)
were used for the odor discriminations and were
mounted using Velcro onto rectangular Plexiglas
bases. Odor discriminations were created by
mixing play sand (148 grams 149 grams) with
different dried spices (i.e., 2 grams of cocoa or
cinnamon and 1 gram of cumin or
cardamom). Procedure The rat was shaped to dig
in unscented cups of sand for two days prior to
training He received one day of training for each
odor discrimination. For the cocoa/cinnamon
discrimination, the distinction was made by
adding corn puffs in the cocoa cup. Whereas, for
the cumin/cardamom discrimination, the cup
containing cumin contained either four fruit
loops or four corn puffs in random order. The
position of the cups were also randomly changed
(left vs. right). The rats latency to dig in
either of the cup was measured by a stop
watch. On the day of the testing the rat was
presented with cups containing cocoa and cinnamon
sans the rewards. His latency to dig and the time
spent digging on each cup was to be recorded
using the stop watch. The cup preference was to
be calculated using the following formula Cup
preference time spent digging on each cup/
total time (300 seconds)
Training (Day 2) Two cups of scented sand (cumin
vs. cinnamon) eight trials with 75 correct total)
Testing (Day 5) Two scented cups (cocoa/cumin)
presented without rewards.
References Chance, P. (2006). Learning and
behavior Active learning edition (5th ed.).
Belmont, CA Thomson/Wadsworth.