BEHAVIOR OF STOCK AND INBRED ALBINO RATS 



287 



record. All eight of the rats in group 2 (tables 7 and 8) on 

 the other hand, were capable of carrying discrimination as far 

 as condition 6, i.e., cardboard versus milk glass and 4 papers. 

 One stock rat stopped there. The other three stock animals 

 went as far as condition 7, where also one inbred male halted, 

 while the other three were able to discriminate until condition 

 8 (milk glass and six papers) was reached. The inbred rats 

 therefore were able to discriminate under more difficult con- 

 ditions than the stock rats. 



(3) Two of the stock rats of group 2 after experiencing the 

 electric shock several times under condition 1 made their choices 

 so carefully that only one further error occurred before they 

 reached the limit of their discriminating ability. At that point 

 they were so disturbed by the shocks received that it was im- 

 possible to work further with them. Even when the others 

 were ready for the review series they still refused to attempt 

 to discriminate at all. These two rats finished in 24 and 25 

 series of trials as against 34 and 35 for the others. The average 

 number of trials required to discriminate perfectly under con- 

 dition 1, condition 2, and the total number of trials (exclusive 

 of review series) given in the discrimination apparatus are 

 shown in table 9. 



TABLE 9 

 Average Number of Trials in Discrimination Apparatus 



Condition 1 . 



Condition 2. 



Totals of all conditions 



Stock 



females 



41.6 



32.5 



33.3 

 27.5 



96.6 

 150.0 



Inbred 



females 



51.6 



32.5 



33.3 

 32.5 



102.3 

 172.5 



Stock 

 males 

 43.3 

 30.0 



30.0 

 22.5 



91.6 

 150.0 



Inbred 

 males 

 76.6 

 32.5 



33.3 

 30.0 



133.3 



175.0 



Group 1 

 Group 2 



Group 1 

 Group 2 



Group 1 

 Group 2 



From this table it appears that the inbred rats, especially 

 those of group 1, required a larger number of trials under con- 

 ditions 1 and 2 in order to acquire the habit of discriminating 

 perfectly than did the stock rats. The stock females. of group 

 1 averaged lowest, stock males next, then inbred females and 

 inbred males. Of group 2, the stock males required fewer 

 trials, then the stock females, inbred females and inbred males. 

 Since the inbred continued the experiments under more diffi- 



