TRIAL AND ERROR REACTIONS IN MAMMALS 55 



(6) The immature monkey's curve differs radically from 

 that of the miature monkey's in that it ascends continuously 

 and rather sharply from A to B to C, attaining its greatest height 

 at C; the descent from C to D to E is likewise sharp and con- 

 tinuous. The curve is lower at A and higher at E than is the 

 mature monkey's curve at these points. 



(7) The mature dogs' curve makes a considerable ascent from 

 A to B; drops to the base line at C, from which it ascends to its 

 maximum height at D; and makes a slight descent from D to E. 

 In view of the fact that with prolonged experience the dog 

 tends to manifest C reactions only, the absolute absence of these 

 reactions, as reflected by the position of C in their curve of dis- 

 tribution, is of considerable interest. 



(8) The older puppies' curve ascends from A to B; descends 

 slightly from B to C, after which it ascends slightly to D; and 

 ascends sharply to attain its maximum height at E. 



(9) The younger puppies' curve, when compared with that 

 of the older puppies', affords us material of some value for 

 ontogenetic interpretations, since the averages for these two 

 groups include a considerable number of subjects. In both 

 curves, A is relatively near the base line, but in the younger 

 puppies' curve there is a descent from A to B, as compared 

 with an A to B ascent in the older puppies' curve. From C 

 to E both curves ascend continuously, but the younger puppies' 

 curve makes a sharper ascent, and is higher at E. 



(10) The mature cats' curve bears a striking resemblance 

 to that of the mature dogs, the only points in which they are 

 essentially different being as follows: (a) The mature cats' 

 curve is slightly above the base line at C, whilst in the case 

 of the mature dogs it is coincident with the base line at C; (b) 

 the mature cats' curve ascends from D to E, attaining its max- 

 imum height at E, whilst the mature dogs' curve slightly 

 descends from D to E. It is quite possible that averages for 

 large number of cats and dogs would eft'ace these differences. 

 It may be stated, however, that the writer's experience with 

 these two classes of subjects leads him to believe that the average 

 cat is more prone to manifest the Type E reaction than is the 

 average dog. 



(11) The kittens' curve has many points of similarity with 

 the older puppies' curve; it ascends from A to B; descends from 



