DELAYED REACTION 21 



ous methods have been made to yield ample returns for this 

 purpose. The crux of the matter is that the methods them- 

 selves are inadequate for the solution of the problem. Let 

 me re-emphasize the fact that if comparative psychology is to 

 postulate a representative factor, it is necessary that the stim- 

 ulus represented be absent at the moment of response. If it 

 is not absent, the reaction may be stated in sensori-motor 

 terms. But in order to know that the stimulus is absent, it 

 is first necessary to determine carefully what the stimulus is. 

 None of the methods reviewed, I believe, meet these require- 

 ments. Whether the tests presented in this monograph do or 

 not, the reader himself may judge. 



III. NOTES ON THE ANIMALS AND CHILDREN TESTED 

 Four classes of re-agents were used in the experiments whose 

 description is to follow: white rats, dogs, raccoons (Procyon 

 lotor) and children. A few words descriptive of these subjects 

 will not be amiss. 



1. Rats 



Twenty-two rats were used during the entire course of the 

 experiments. Five of these were normal adults and were used 

 only in preliminary tests in which the purpose was the perfec- 

 tion of a method. The remaining seventeen (normal) were all 

 started in the experiments when approximately four weeks old. 

 All were vigorous, healthy animals whose records may stand 

 as t}^ical. 



2. Dogs 



The two dogs tested were mongrels in whom the rat terrier 

 strain was dominant. They were very bright and intelligent 

 looking, very active, playful and affectionate, — indeed they 

 seemed to possess all the qualities that are attributed to intel- 

 ligent dogs in countless anecdotes. This was the unanimous 

 testimony of many observers. The two dogs, Blackie and 

 Brownie, both females of the same litter, were secured from 

 an animal dealer when they were small puppies and were started 

 on the preliminary tests at about the age of five months. They 

 were usually kept in a kennel out of doors and remained in 

 excellent condition during the experiments. Of the two. Brownie 

 was the more aggressive and, to the ordinary observer, appeared 

 possibly the more intelligent. 



