INDIVIDUALITY, TEMPERAMENT, AND GENIUS IN ANIMALS 237 



to contrast the two strains by saying 

 that the one is the more or the less 

 intelligent. 



Subsequently, increasingly definite 

 and well-controlled studies were made, 

 in which were recorded observations 

 concerning the preferred position of an 

 individual in its cage or nest box; the 

 relative positions at different hours of 

 the two individuals, male and female, 

 in a given cage; the degree or amount 

 of activity; savageness, or the tendency 

 to bite; and the quickness and amount 

 of response to various stimuli. These 

 and similar observations shortly indi- 

 cated that savageness designates certain 

 tendencies to reaction, as does also fear, 

 timidity, or wildness, and that our only 

 intelligible way of defining these terms 

 is by enumerating the several types of 

 activity. Wildness, for example, is 

 indicated by attempts to hide in the 

 cage or in the observer's hand, random 

 and excited running about with re- 

 peated attempts to escape, squeaking, 

 and various other forms of response. 

 Timidity, which seemingly is not iden- 

 tical with wildness or fear, involves the 

 avoidance of the experimenter, a kind 

 of chattering or gnashing of the teeth, 

 cowering, or even trembling. 



Although most of our studies have 

 been concerned with relations of beha- 

 vior to inbreeding or to the crossing of 

 individuals which differ markedly in 

 some trait, we have incidentally ob- 

 tained abundant evidence of important 

 individual differences of the tempera- 

 mental sort.i One rat, for example, is 



• Basset, G. C. Habit Formation in a Strain of 

 Albino Rats of Less than Normal Brain Weight. 

 Behavior Monof/raphs, 1914: 2: Serial No. 9. 



Yerkes, Robert M. The Heredity of Savage- 

 ness and W^ildness in Rats. Journal of Animal 

 Behavior, 1913: 3: 286-296. 



Yerkes, Ada W. Comparison of the Behavior of 

 Stock and Inbred Albino Rats. Journal of Ani- 

 mal Behavior, 1916: 6: 267-296. 



Utsurikawa, Nenozo. Temperamental Differ- 

 ences Between Outbred and Inbred Strains of the 

 Albino Rat. Journal of Animal Behavior, 1917: 

 2: 111-129. 



extremely fearful of anything new or 

 unusual, it shrinks timidly from the 

 experimenter. It can only with diffi- 

 culty be induced to try to find its way 

 through the experimental apparatus. 

 When cornered, it defends itself by bit- 

 ing the experimenter's hand. Its wild- 

 ness is indicated by persistent efforts to 

 hide or to escape. It responds quickly 

 and markedly to any sudden and un- 

 expected stimulus; peculiarly startling 

 stimuli at times cause it to tremble. 

 Another individual of the same age and 

 sex, born in the same litter, is by con- 

 trast aggressive and exhibits marked 

 initiative in new situations. Its fear or 

 timidity is readily overcome by its curi- 

 osity. It quickly becomes accustomed 

 to the experimenter, and allows him to 

 touch it or take it up in his hand with- 

 out attempting to bite, and shortly 

 without effort to escape. It responds 

 slowly and only slightly to most stimuli 

 and is disturbed only by strong stimu- 

 lation. In a word, the two rats are 

 temj^eramentally as different as any 

 two human beings one is likely to meet. 

 It is such observations as these, made 

 on many different individuals, that 

 have wholly convinced us of the desira- 

 bility of a careful analysis of tempera- 

 ment and the reduction to terms of 

 measured description of its chief con- 

 stituents. 



We once undertook to study experi- 

 mentally the ideational behavior of 

 pigs. For this purpose two young ani- 

 mals were chosen, the one a male, the 

 other a female. They were observed 

 daily, and for several hours each day, 

 the whole of one summer. We became 

 sufficiently well acquainted with their 

 characteristics to appreciate alike their 

 varying degrees of intelligence and 

 their temperamental peculiarities. What 

 we have not published in our report 

 on the behavior of these creatures 



