TRIAL AND ERROR REACTIONS IN MAMMALS 63 



severation " exists, it is apt to find expression in the continuous 

 persistence of both useless activities and useless avoidances of 

 activities. The katatonic who continues a motor impulse to 

 the point of catalepsy, or who utters a single word for hours 

 without interruption, is always a patient in whose behavior 

 we expect also to find inordinate persistence of inhibitions. My 

 investigation of normal behavior has disclosed the same asso- 

 ciation of the one phenomenon with the other in the case of 

 dogs, cats, a horse, and a human infant. The fifth trial of the 

 infant affords an example of this; he tried the various doors 

 in the following order: 3-1-3-4-1-4-3-4-4-4-3-1-4-3-2. Even 

 more striking is the fifty-ninth reaction of Cat 5, who tried 

 the doors in the following order: 3-4-1-3-3-1-3-4-4-1-3-1-3-4- 

 4-1-4-3-2. In each case there are apparent both types of per- 

 severation. 



VI. SUMMARY AND CONCLUSIONS 



The above interpretations of Types A, B, C, D and E re- 

 actions in terms of reactive tendencies to which they may be 

 ascribed now enable us tentatively to assign psychological 

 values to the genetic curves of distribution in figure 3. 



(i) The rational inference tendency (Type A) is clearly ap- 

 parent in the behavior of only the eight normal human subjects 

 whose ages range from eight to thirty-four years, and in the 

 behavior of defective Boy A. Morgan's (10) law of parsimony 

 as applied to interpretations of behavior, requires us to assign 

 the behavior of all other subjects, including that of defective 

 Man A, to lower reactive tendencies. We have not ruled out 

 the possibility, of course, that with sufficient experience any 

 of the subjects would manifest a sufficient percentage of Type 

 A reactions to indicate the presence of the rational inference 

 tendency; nor that the subjects who manifested relatively 

 low percentages of these reactions were wholly uninfluenced by 

 the tendency in the question. 



(2) The unmodified searching tendency (Type B) finds its 

 most frequent expression in the behavior of defective Man A. 

 Among adult animals, the monkeys rank first in this respect, 

 the dogs second, the cats third, and the horse fourth. Of all 

 the subjects, taken as individuals and without regard to age, 

 the horse seems to have been least affected by the unmodified 

 searching tendency. 



