The Effect of Temperature Changes upon the Behavior of the White Rat

Abstract

Today, it is recognized that a wide range of environmental forces must be considered as co-operative factors in the development of the organism. Changes in temperature have been found to be an important aspect of these influences. The physical and behavioral characteristics of many organisms change as the temperature under which they live varies. The purpose of the present study is to determine the influence of changing temperature upon the maze behavior of the white rat. Three well insulated rooms were equipped to house about sixty rats each. A refrigeration unit maintained a temperature of 55-58? F in the cold room. The temperature of the control room was kept the same as the rest of the building. The usual range was a few degrees above and below a mean of 75?. The hot room was equipped with a small electric heater which maintained a temperature of 88-90? F. Adequate ventilation was provided for all three rooms. The litters from thirty female albino rats were used as the experimental animals. At twenty-eight days of age, rats in these litters were weaned, marked, and divided so that one-third of each litter was placed in each of the three rooms. Sex and average weight at the time of division were equated. Weekly weight records were kept throughout the course of the experiment. During maze running, daily weight records for each rat were taken. Approximately forty-five rats in each room were required to learn a simple four-alley maze. Records of trials, errors, and time were kept, and the criterion of learning set at three successive errorless runs. After learning the maze, the rats in each room were divided into three sub-groups, equated on the basis of sex and average trials required to learn the maze, and were then placed in the various rooms. For example, in the cold room one sub-group of 15 was left in that room. A second sub-group, equal in average trials required for mastery of the maze, was placed in the control room. The third subgroup was moved to the hot room. The same procedure was carried out with the rats learning the maze in the control and hot rooms. Forty days after original learning, the rats in the three rooms relearned the maze. Again the criterion of learning was three consecutive errorless runs, and the same records of time, trials, and errors were kept. After relearning, all rats in the three rooms were tested in a modified obstruction box. The grid of this box was connected to a small induction coil, and the voltage checked frequently to insure constant current value. Fifty rats in each room were tested, and it is believed that with such large groups representative results can be obtained without elaborate precautions to insure exactly the same shock to each rat. Daily weight records during grid tests were also taken. At the end of the experiment the rats were killed and the body lengths and tail lengths measured.