BEHAVIOR OF VERTEBRATES 435 



improbable ; that the conditions do not answer to those of modern 

 psychology, zoology or the methods of the psychology of the 

 senses; and that a profitable discussion is not possible unless 

 the experimental work can be scientifically controlled. 



Claparede tries to refute these statements and says that the 

 method of protestation is not a scientific method. He insists 

 that he witnessed tests where correct responses were given under 

 conditions which absolutely excluded the possibility of guidance 

 by voluntary or involuntary signals. But Claparede did not 

 succeed in getting correct answers under conditions where the 

 answer was unknown to those present and Edinger affirms that 

 in his presence any attempt in which the solution was unknown 

 to the attendant did not succeed. 



What has been said of the horses applied equally well to the 

 Mannheim dog of which Mackenzie writes and to the horse 

 reported by O'Shea. 



The presence or absence of ideas in animals always furnishes 

 a fruitful field for discussion. In the beginning of his mono- 

 graph on the delayed reaction, Hunter (28a) examines the 

 different lines of evidence offered to prove the presence of such 

 ideas. He then defends the thesis, by means of arguments 

 backed by his experimental investigation, that no ideas need 

 be postulated in a sensory-motor act where the stimulus is 

 present at the moment of the response and that when the brief 

 stimulus and response are separated by an interval the "carry- 

 ing over" may be by other means than ideas. 



Rats, dogs, raccoons and children were trained to go in a 

 definite, though variable, direction, which was indicated by a 

 light previously exposed at the place. The time between the 

 exposure of the light and the release of the subject was then 

 increased as far as possible without destroying the habit. It 

 was found that the maximum delay consistent with a successful 

 response in rats was only 10 sec, in dogs 5 min., in raccoons 25 

 sec. and in children 25 min. The delay of a child of two and 

 one-half years, however, was less than 1 min. The great sig- 

 nificance of the work was not so much in the length of this 

 interval as in the behavior during the interval. The rats were 

 enabled to overcome the delay by preserving a definite orienting 

 attitude of the whole body and the dogs by overt orientation 

 of the head. The raccoons and children maintained no such 



