Difficulties and Methods n 



psychology, published in 1886 an experimental study of the 

 behavior of the starfish. Loeb's work on the reactions of 

 animals to stimulation began to appear in 1888. Max 

 Verworn, the physiologist, published in 1889 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 McGill 

 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 research was to place his animals (chicks, cats, and 

 dogs) under the most rigidly controlled experimental condi- 

 tions. 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 appearance of Thorndike 's work the performance 

 of experiments upon animals has played much part in the 

 .work of psychological 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 comparative psychology. 



Despite the obvious advantages of experiment as a 

 method for the study of animal behavior, it is not without 



