BEHAVIOR OF STOCK AND INBRED ALBINO RATS 291 



relation to timidity. It could not be measured at all in the 

 maze experiments but in the discrimination records those rats 

 were judged not particularly sensitive which rushed back into 

 the dark box immediately after receiving a shock. 



In activity, as shown in the discrimination experiments, the 

 rats varied greatly. Some made their choices carefully, with 

 due caution, and with strict attention to business. Others 

 wouM investigate the box thoroughly, try to climb out, stretch 

 heads into the discrimination chambers, stop to eat, etc After 

 a shock several, especially the inbred rats, would become greatly 

 excited, trying repeatedly to climb over the walls. 



In regard to the time taken for each choice the timidity of 

 the animals expressed itself in various ways. The quickest time 

 in which the discrimination could be made was A". No. 89, 

 inbred male, made an average for ten trials in preference series 

 A of .7", and B of .6". After making two mistakes in training 

 series 1, he was apparently panic-stricken, resisted being urged 

 to enter again, crouched in the alley, darting back to the food 

 box several times. When finally he entered the discrimination 

 chamber he crouched by the door of the dark box, gazing into 

 it without moving for over half an hour. Repeatedly after 

 being shocked he would try frantically to jump out over the 

 edge of the passage. He was large, quick, strong, and active, 

 and when discrimination was easy, made quick trips and quick 

 but careful choices. 



The other inbred male (No. 87) showed his timidity in exces- 

 sive resistance to entering the discrimination box. He would 

 crouch in the passageway in front of the swing doors, and it 

 required much ingenuity and some force to persuade him to 

 enter without getting hurt in the process. Once inside, how- 

 ever, in early experiments, he would dash to one of the boxes, 

 halt abruptly to make a quick comparison with the other, dash 

 in and around to the food box as fast as he could go. All of 

 his choices even when discrimination became difficult, were 

 made quickly but always after careful comparison of the two 

 chambers. 



Three of the four inbred rats, even in the preference series 

 where there was no shock to frighten them, were at first too timid 

 to eat when they returned to the food box. One of the females 

 invariably tried to climb out of the small hole in the cover of 



