EFFECT OF LENGTH OF BLIND ALLEYS ON MAZE LEARNING 7 

 THE EXPERIMENT 



The experiment was carried out in the University of Chicago 

 during the months of July and August, 1916. n Twenty-four 

 white rats, ranging in ages from about five to six weeks at the 

 time of the beginning of the experiment, were used. Of these, 

 nine were males and fifteen females. These were at first divided 

 into two main groups, the one consisting of. the fifteen females 

 and one small male 12 and the other of eight males. The first 

 group began as untrained animals in the B -mazes, to be described, 

 and the second in the A-mazes. They were ear-marked and 

 grouped about eleven days before the experiment began, during 

 which time they were habituated to handling, and were fed 

 'daily in the food box of the maze (in the separate groups) except 

 a couple of days while the maze was out of the laboratory for 

 remodeling. The food was bread soaked in milk, a definite 

 quantity being given each day to insure uniformity of bodily 

 conditions and of hunger. During the entire period of prepara- 

 tion and experimentation not a single rat showed any signs of 

 illness. The two main groups were again divided into control 

 groups, as will be explained later in " The General Schedule 

 of Experiments." These sub-groups were caged separately for 

 convenience of experimentation, but they were fed together 

 daily in the food box of the maze throughout the time of the 

 experiment and were also interchanged daily in the cages, i. e., 

 each sub-group was on any given day put into the cage occupied 

 by its control group during the previous twenty-four hours. 

 The purpose of these interchanges was to prevent the develop- 

 ment of group odors. 



Only one maze in the laboratory was available. This was, 



11 1 desire to express my thanks here to Professors Angell and Carr for the privi- 

 leges of the laboratory and for the animals used in the experiment. With the 

 exception of aid from my brother, John C. Peterson, a graduate student in the 

 University of Chicago, I am wholly responsible for the experiment, both as to prob- 

 lem and method. My brother helped me plan the modifications of the maze avail- 

 able, and to get started with the experiment, which help I gratefully acknowledge. 

 We had planned to carry on the experiment together, but it was found after the 

 second day of experimentation that one person could record all the movements 

 satisfactorily and could secure greater uniformity in the conditions of the experi- 

 ment than was possible to two. 



12 Through an oversight at the time of the segregation and ear-marking of the 

 animals the small male, No. 10, was classed as a female.' The error was noticed 

 on the fourteenth day of the experiment, and after this time the rat was caged with 

 the males, 5, 8, 1, and 7, but it continued to run the IB maze with the females. 

 No difference from this change was noted in the behavior of the male or of any 

 of the other animals. No. 10 did not continue with the females in any other maze, 

 as will be seen in the schedule. 



