260 HARVEY CARR 



environment. It is thus possible to alter the sensory conditions 

 of the animal while running the maze, or to effect changes in 

 the environment prior to the test. 



Various maze patterns were employed in the experiments. 

 Unless otherwise stated, the mazes were of the usual type with 

 the exception that they were almost water tight and covered 

 by closely fitting glass covers. These features are mentioned 

 because presumably they may effect the sensory relation of the 

 animal to the extraneous environment. In order to alter the 

 objective environment of the maze, recourse was had to a canvas 

 top. A light but rigid frame was constructed and placed upon 

 the maze. Over this was stretched several thicknesses of canvas 

 fastened at the top but hanging loose on the four sides. From 

 the top was suspended an electric lamp. The interior could 

 thus be illumined or darkened, any of the four side curtains 

 could be raised or lowered, or the whole top could be removed 

 or replaced at will. 



This paper describes the experimental results on animals with 

 intact sense organs. Nearly two hundred rats were utilized in 

 the various tests. Some of the results were secured by students 

 working under my direction. The majority of the tests were 

 performed by the writer. 



The disturbances induced by the alterations were measured 

 in terms of the error record. These records embrace such 

 features as the number of animals affected, the number of trials 

 in which error was present, the number of errors, the length of 

 time necessary to adapt to the novel situation, and the tendency 

 for the disturbing effect to be carried over to subsequent tests 

 under normal conditions. 



EXPERIMENTAL RESULTS 



A. Alteration of conditions previous to running the maze. 



Variable Route. In the typical experiment the living cage 

 is kept on a rack some distance from the maze and the animals 

 are carried by hand and placed within the maze. This route 

 was kept constant while the maze was being mastered. After 

 mastery this route was altered in various ways. Sometimes a 

 long and devious route through the laboratory was chosen. 

 Fourteen rats were tested and no disturbing effects were noted. 



Method of Handling. The normal method of handling was 



