Abstract
This study of rat behavior seeks to show the role of sucrose presented in different forms: liquid, pellets as the reinforcer of rat behavior in laboratory conditions.
The research is based on empirical methods and theoretical studies and similar experiments in the literature. The hypothesis of the experiment is proved by careful analysis of statistical and quantitative data using necessary statistical tools. The results of the research may be helpful for the practitioners and researchers interested in applying the findings of behavioral science in medicine, psychology, and biology.
Introduction
Research on rat behavior is an essential part of behavioral studies which are very fruitful for the development of neurophysiology, innovative medicine approaches, animal behavior disciplines, and biology in general. Rats were traditionally used as the dominant object for research experimentations as their biological and behavioral reactions are the most appropriate for hypothesizing and laboratory research. A Skinner box with necessary inventory is usually used as a tool for conducting experiments.
There is no denying the importance of the fact that the secure normal passing of experiments and well-grounded scientific results, one should formulate and use a sound methodological base of research and elaborate genuine hypothesis. If this is done, we are likely to obtain significant results.
As it was noted, experimentation on rates is widely used and its theoretical and practical results are significantly covered in the literature.
For instance Kawai, N., & Nakajima, S. Provide the outline of rat experiments on so-called ‘comfort’ responses which were conducted to investigate the role of the passive maternal stimulus on the immobility of 9-and and the 16-day rat pups (1997). As the experiment shows that there was a significant increase in dorsal immobility which may essentially reduce struggling between pups in the presence of their mother and hence help rat mothers to transport the infants back into their nest.
As Campbell’s analysis of locomotion shows during the second week of a rat’s life it increases as the struggle for survival becomes dominant.
Some other experiments were aimed at investigating the consequences of home separation on rats’ fear responses. Their research found that in the case of passive home stimulus availability the heart rate is increased and the general level of anxiety grows.
Another branch of research investigates behavioral responses to food and flavors. Ward et al. found out that rats acquire preferences of separate flavor as a conditioned stimulus and mixed flavors with some additional substances as unconditional. This happens because if all that rats learned was only the association between a given flavor and a certain reaction being evoked by nutrient – in this case, satiation treatment would not affect the preference of flavor.
Some other experiments were conducted to analyze the impact of stress and alcohol reactions on fetal development in male rats. Kawai, N., & Nakajima, S. (1997) show that exposure to stress is a significant factor in lowering rats’ ratio of copulation but not significantly affecting ejaculation. Alcohol exposure is not reported as a factor in lowering sexual activities. However, when alcohol is combined with stress effects it is likely to substantially affect low sexual activity in rats (Carlson, 2007).
Another important experiment was conducted in the 70s and is known as Rat Park. It was designed to prove the hypothesis that the drugs do not result in addiction and that evident rat addiction to morphine can be attributed to living conditions but not drugs themselves. As the experiment showed, rats that were given morphine when they were consequently provided with a choice of water with or without morphine, chose plain water.
Information for the method
As some previous studies show, the rat’s response to low-concentration sucrose reinforces, will see an increase in terms of the food-pellet rather than liquid-sucrose.
The current experiment examines whether the upcoming sucrose-pellets reinforcement can produce an effect similar to the abovementioned. We chose the sucrose pellet for several reasons. First of all, it significantly differs from the previously used food pellets in a number of ways such as taste, color, nutritional values. Hence, it was possible to compare every produced induction (Bouton, 2007).
Method
Subjects. The subjects are eight experimental male Dawley rats. These subjects were kept individually, had their free access to water (only), and were deprived of food for the period of 2 weeks. They also experienced 14/10 hours dark/light schedule. Besides this, the subjects were kept at approximately 85 % of the free-feeding weight due to the use of special feeding methods.
Apparatus. The apparatus is the experimental Skinner box for rats. It was located a 5cm responding lever near the left edge of the front panel and above 8cm from the grid floor.
This lever was extended to 2 cm within the chamber. It was required a 0,25N force to depress this lever. A similar lever was located on the right side of the panel. However, it should be noted that it was not utilized in this given experiment. We also used stimulus lights – 3cm in diameter which were located above each lever.
Besides this, we used a liquid-drop dispenser and the pellet dispenser which were put at the front panel. Both dispensers could give reinforcers into the 3cm diameter cup located in the box. We centered the houselight at the back wall of the chamber and it was approximately 2cm below the room’s ceiling. The technical equipment was also used for lowering the noise level and the experimental events programmed and data gathered using IBM computer which ran special software.
Procedures: Rat subjects were trained in order to press the left lever using the method of shaping by successive approximations. When each rat pressed the lever more than one hundred times, it could participate in the experimental procedures.
Subject rats had to respond in the sessions, approximately 50 minutes in length. The left lever had to be pressed on the random interval throughout the given session. The reinforcers used were programmed at the probability of 0,0167 every one second as a certain reinforcer was not yet scheduled for the delivery.
There is no denying the importance of the fact, that the pattern supposed that the scheduled reinforcer should have been used before the next interval began. During the session, the above light and the houselight were illuminated.
During the experiment, three types of experimental conditions were used. In the first type of condition (Suc-such), 0,2ml of the liquid sucrose played the role of reinforcer during all the sessions. In another type (Suc-FoodPel), the liquid-sucrose reinforcers were given during the first half of the full session and Noyes 45-mg sucrose-pellet was utilized as the reinforcer during the second half of the session. Each type of experimental condition was used during a total of 20 sessions which were conducted daily, from five to seven days per week.
Experiment subjects were divided into 2 separate groups. The first group of experimental rats was responding for 1% sucrose (mixed with the tap water) and the second group was responding for the 5% liquid sucroses. The following order of conditions was given to one pair of the subjects from each group: Sucrose-SucrosePellet, Sucrose-FoodPellet, and Sucrose-Sucrose. Another pair of experimental subjects were receiving a reverse order of experimental conditions.
The sucrose concentration was changed for each group if they managed to complete all three conditions. Each pair of rats then had to respond to the same conditions but in reverse order, as they experienced them during the previous session.
Results and Discussion
The table shows the subject’s response to experimentation conditions in the fixed and variable intervals which correspond to Sucrose-Sucrose, Sucrose-FoodPellet, and Sucrose – SucrosePellet situations. The empirical results represent standard error for responding in 2 minutes intervals.
As the results represented in the table show, during the first half of the session, the induction was essentially present. For both levels of sucrose concentration, the response was higher during the first half session, than when food and sucrose pellets were utilized as the reinforcer during the second half of the session.
There is no denying the importance of the fact that the availability of induction did not significantly vary among different pellet types. And thirdly, all pellets provided higher levels of response during the second half of the session than liquid-sucrose concentrations.
Statistical analysis also confirms these hypotheses. Rats respond higher for 5% sucrose than for 1% sucrose and the rate of response significantly varied depending on the half of the session and the type of reinforcer used. However, it should be taken into consideration that the substantial effect of chemical reinforcers during the second halves of the session does not mean that the effect of liquid sucrose and sucrose pellets was equally strong during the second half of a session.
It was also found out that the pellet type of reinforcer does not significantly change experimental results. However, the effect of 5 minutes intervals was significant and it indicated that the rates of response varied during the first halves of the session when the pellets were given during the second halves of the session.
Other effects did not reach the mark of statistical significance. Hence, the abovementioned results support the point of view that the induction could be observed when rats were responding to either 1 or 5% sucrose, and both types of experimental pellets produced the same induction effects.
Responses to the second halves of the sessions showed that different reinforcers maintain varying response levels and rates and these rates significantly change during the second half of the session, accordingly. The interactions between the level of sucrose concentration and the second-half reinforcers were found as significant.
The statistical analysis has proven that a 5-minutes interval is the most significant in defining response levels during the second half of the session and less significant during the first half.
The total results of this experiment show that the induction which was produced by the upcoming reinforcers can not be limited to the utilization of food pellets. Similar induction results were produced by using the solid sucrose pellets as a reinforcer. These results may be the source of certain generalizations. It seems that the abovementioned results run contrary to the idea that the difference in taste between different reinforcers plays its role in the process of induction. However this experiment does not provide empirical grounds for such kind of conclusion, it shows that the opposite point of view is not relevant.
To sum it up, the experiment was conducted and the hypothesis set was proved by the empirical data collected.
References
Bouton, M.E. (2007). Learning and Behavior: A Contemporary Synthesis.
Carlson, N.R. (2007). Physiology of Behavior. 9th edition. Needham Heights, Mass: Allyn and Bacon.
Kawai, N., & Nakajima, S. (1997). US Postexposure Effect on Conditioned Flavor Preference in the Rat. The Psychological Record, 47(3), 499.
Schwartz, B. and Robbins, S.J (1998). The psychology of learning and behavior. (4th Ed.). Norton.
Ward, O. B., Ward, I. L., Denning, J. H., Hendricks, S. E., & French, J. A. (2002). Hormonal Mechanisms Underlying Aberrant Sexual Differentiation in Male Rats Prenatally Exposed to Alcohol, Stress or Both. Archives of Sexual Behavior, 31(1), 9.
Wilson, C., & Kaspar, A. (1994). Changes in Immobility Responses in Rat Pups with Maternal Stimuli. Journal of General Psychology, 121(2), 111-120.