Rat Observation Report

The experiment examined the reward magnitude and negative contrast effects on rats operant-lever response performance. The experimental design was both between and within subject design. The subjects were eight Sprague Dawkey females rats who were randomly assigned to a group that received 16% of sucrose ( n=4) and another group received 4% of sucrose ( n=4) which was the control group of the experiment. Both groups were deprived of water for 23 hours and had food access. The preshift sessions were from 1-9 and post-shift was only session ten in which both groups received 4% of sucrose. The results of a mixed factorial ANOVA design indicated during the preshift phase the 16% group responded to a significant higher rate than the 4% group resulting …show more content…
Experiment consisted of five groups of 12 rats which were given twenty daily training in a straight runway and were rewarded with 1, 2, 4, 8, or 16, 20 mg of food pellets. Fourteen day before the experiment, the rats were food trained with complete water access and restricted food access for only one hour. Only one trail was performed each day for twenty days. The last day reward was one pellet for all five groups. As a result, rats’ performances were increased as reward was increased. Implying that negative contrast is governed by learning and the rewards gradually increased as the reward …show more content…
For the preshift phase, a 2 x 9 mixed factorial ANOVA designs was conducted and postshift a repeated measure of t-test was conducted. Preshift were first nine sessions, one group received 16% of sucrose other group received 4% of sucrose. Postshift phase, tenth session all groups received 4% of sucrose. Sessions of VR training was sessions 1-9 in this 2 x 9 ANOVA. In this preshift, the main effect of the group was significant, F (1, 6) = 6.272, p < 0.04. Group 1 of 16% of sucrose ( M= 0.40; SEM = 0.04) and group 2 of 4% of sucrose (M=0.25; SEM= 0.04) differed in their response rates. The group that was receiving 16% of sucrose responded at a higher rate than the 4% group of sucrose. Main effect of the Session was significant as well, F (8, 48) = 4.801, p < 0.01. However, Group x Session interaction was not significant, F (8, 48) = 1.99, p < 0.067. Overall, during the pre-shift phase the main effect of 16% group responded more than the 4% group. For the post-shift, the independent samples t-test was significant at session ten, t(6) = 2.553, p < 0.04. The group differed in terms of response rate. 16% group (M= 0.21; SEM=0.02) responded at a significantly lower rate than the 4% group (M= 0.28;