TEMPERAMENTAL DIFFERENCES BETWEEN 



OUTBRED AND INBRED STRAINS OF 



THE ALBINO RAT 



NENOZO UTSURIKAWA 



From Hie Harvard Psychological Laboratory 



INTRODUCTION 



About two years ago the writer sought, in the Harvard Psy- 

 chological Laboratory, training in the methods of comparative 

 psychology, since such training promised to be helpful to him 

 as an ethnologist. A problem was suggested to him by Pro- 

 fessor R. M. Yerkes, — evidently difficult and yet extremely 

 fascinating. Its thorough study would certainly require years 

 of diligent work. But the writer, because of his ethnological 

 interests, was able to give only one year to this psychological 

 investigation. 



Obviously enough, from what follows, the ' materials to be 

 presented are fragmentary and inadequate for the description 

 of the differences in the strains of rat. Still, to throw them 

 away would seem too extravagant. With a humble sense of 

 obligation, the writer offers his limited data to the scientific 

 world. He wishes to take this opportunity to thank Professor 

 Yerkes, Dr. R. M. Elliott, and Dr. W. R. Miles, for valuable 

 assistance in the work. 



PROBLEMS 



The chief problem was to discover, if any, the temperamental 

 differences between outbred and inbred strains of the albino 

 rat. Such features of behavior as degree of nervousness or 

 timidity, of savageness and wildness, of sensitiveness to stimuli, 

 of persistence in response, quickness of response, and so on, may 

 be recorded as constituting the temperament of an animal. In 

 the terms of psychology, and in the last analysis, perhaps, tem- 

 perament is identical with the threshhold, quickness, amount, 

 and steadiness of response to a given stimulus or object. The 



