Difficulties and Methods n 



Verworn, the physiologist, published in 1899 an exhaustive 

 experimental study of the behavior of single-celled animals. 

 With the exception of Preyer and Romanes, all these men 

 had but a secondary interest in comparative psychology: 

 Bethe, indeed, as we shall see, wholly rejects it. Lloyd 

 Morgan, who has written instructively on comparative 

 psychology, makes but a limited use of the experimental 

 method. Wesley Mills, professor of physiology in Me Gill 

 University, has studied very carefully the mental develop- 

 ment of young animals such as cats and dogs, but is inclined 

 to criticise the use of experiment in observing animals. The 

 work of E. L. Thorndike, whose " Animal Intelligence " 

 appeared in 1898, represents, perhaps, the first definite effect 

 of the modern experimental movement in psychology upon 

 the study of the animal mind. Thorndike's aim in this re- 

 search was to place his animals (chicks, cats, and dogs) under 

 the most rigidly controlled 1 experimental conditions. The 

 cats and dogs, reduced by fasting to a state of "utter hunger," 

 were placed in boxes, with food outside, and the process 

 whereby they learned to work the various mechanisms which 

 let them out was carefully observed. Since the appear- 

 ance of Thorndike's work the performance of experiments 

 upon animals has played much part in the work of psychologi- 

 cal laboratories, particularly those of Harvard, Clark, and 

 Chicago universities. The biologists and physiologists have 

 continued their researches by this method, so that a very large 

 amount of experimental work is now being done in compara- 

 tive psychology. 



Despite the obvious advantages of experiment as a method 

 for the study of animal behavior, it is not without its dangers. 

 These were clearly stated by Wesley Mills in a criticism of 

 Thorndike's " Animal Intelligence" (273). They may be 

 summed up by saying that there is a risk of placing the 



