Allen, Association in the Gumea Pig. 309 



At the age of 62 hours evidence of the mother's acting as 

 a specific stimulus is given by the act of the guinea pig in mak- 

 ing a real attempt to get to her through the wires of the box. 

 With many individuals such definite recognition of the mother 

 occurs even later. 



Development varies greatly in individuals. It seems true 

 without doubt that the larger the guinea pig at birth the more 

 active it is, and the sooner it reaches full coordination and the 

 ability to solve problems presented to it (problems which de- 

 pend upon activity). 



From Minot's observations^ it was concluded that the 

 length of gestation is shorter the larger the litter, and the shorter 

 the gestation the smaller the litter. Therefore it is probable 

 that variation in activity and development is a question of ma- 

 turity, since the small animals are in the large litters. In a lit- 

 ter of two, one pig is apt to be somewhat smaller than the other, 

 and to be a few hours behind it in the appearance of character- 

 istics indicative of progressive stages of maturity, e. g. , the 

 jerky running movement which seems to be a good objective 

 criterion of development. 



In spite of their social instincts I have never seen the little 

 guinea pigs play together. There is never anything like mock 

 combats among the young such as form a striking feature of 

 rats' play.^ 



B. Experimental Work. 



Introduction. 



In the experimental work the kinds of problem to be given 

 the guinea pigs were determined by careful preliminary obser- 

 vation of their natural habits and tendencies. No problem 

 should be g-iven to an animal which involves the inhibition of 



* Loc. cit., p. 1 13. 



''■ This small amount of play activity offers a suggestion in favor of the theory 

 of play described in Morgan's Animal Behavior, p. 315. If play is a preparation 

 for the serious defensive and offensive work of adult life, the animal which never 

 makes an attack and has no defence except to run away, could not be expected 

 to spend its youth in sham battles. 



[17] 



