290 



ADA W. YERKES 



were capable of carrying discrimination further than the stock 

 rats, although they required more time and made more errors 

 in doing so. 



An attempt has been made in table 10 to grade these rats 

 in respect to certain characteristics. Since all the animals, 

 when they became accustomed to the surroundings and pro- 

 cedure, would run through the experiments without showing 

 evidences of the timidity and inactivity characteristic of their 

 earlier behavior, the figures given represent the behavior when 

 confronted by new conditions. The characteristics measured 

 are timidity, initiative, sensitiveness, and activity, and the 

 grading is on a scale of 0-5. 



TABLE 10 



Sensitivity 

 No., Timid- Initia- to Activ- Maze Discrimination 



Stock ity tive shock ity 



81c? 1 5 1-2 5 Many errors Hasty choice. Many 



errors. 

 83c? 0-1 4 4 4 Steady, few errors .... Careful choice. Few- 

 errors. 

 85c? 5 ... 5 Fast, steady 



80 9 0-1 4 15 Fast, few errors Careful choice. Few 



errors. 



82 9 5 1 5 Fast, reckless Careful, but much run- 



ning. Excited. 



Inbred 



87c?' 5 13 Quiet 2 days Hard to start. Quick, 



excited. 



89c?' 5 3 3 Quiet 3 days Easily excited. When 



easy, slow, cautious, 

 sure. 



84 9 4 4 3 Fast Businesslike. 



86 9 5 2 4 Quiet 2 days Careful choice. 



On a scale of 0-5, for example, the stock rats showed little 

 or no timidity and great activity; the inbred, on the other hand, 

 just the reverse. Initiative was measured by the readiness with 

 which the rats entered the maze, passed through doorways, or 

 opened by themselves the swing doors of the discrimination box. 

 Sensitiveness was more difficult to measure because of its close 



