440 JOHN B. WATSON 



Yerkes and Bloomfield have reached wholly different con- 

 clusions from their experiments. They made their tests upon 

 two litters of common cats. Their animals were carefully fed 

 upon fresh milk, beef, usually cooked, and fish. They were 

 housed in a room free from mice. In the first week of life the 

 kittens showed no special interest in mice. Shortly after they 

 gained their sight (12 days of age) they were again tested, but 

 the presence of the mice did not elicit the instinctive response 

 sought for. When slightly over four weeks of age three of the 

 first litter of four failed to exhibit the instinct, as before. One 

 of the kittens, however, now exhibited a type of behavior quite 

 in contrast with that of the other three. " She noticed the 

 mouse soon after she had been placed in the cage, as it moved 

 near her, and quickly seized it, growling the while. The mouse 

 escaped and the kitten gave chase, but failed to recapture it 

 before it had climbed to the top of the cage." 



Five days later the kittens were again tested. Nos. 1,2, and 

 3 acted as before; No. 4, as in the above test, made efforts to 

 catch the mouse. Two days later the test was repeated. Kittens 

 I, 2 and 3 showed a marked interest in the mice, but behaved as 

 in the other tests. No. 4 exhibited almost a complete repertoire 

 of movements used by adult cats in catching and killing mice. 

 The mouse was pursued, caught, worried, killed, and partially 

 eaten. The tests were continued upon the remainder of kit.tens 

 belonging to the same group as No. 4, and upon four kittens 

 belonging to a second litter. All the animals tested, at slightly 

 varying ages, exhibited the characteristic instinctive behavior 

 of No. 4. The instinct to kill commonly appears at about the 

 end of the second month. It may appear as early as the end of 

 the first month. Since Berry worked with kittens five months 

 old, his negative results were probably due to the fact that the 

 instinct had waned through disuse. 



A. Franken,'^* in an exceedingly long and diffuse paper, 

 reports some tests on the intelligence of the dog, which are 

 much like those made by Hobhouse several years ago. It is 

 singular that Hobhouse is not quoted as a reference. Thorndike 

 and Lloyd Morgan are the only English references given. Some 

 of the principal statements made by the author are as follows: 

 The characteristic instinctive movements of the dog are con- 

 cerned directly with the goal (obtaining of food). His method 



