64 STELLA BURNHAM VINCENT 



June 29. Thus far the rats are showing no signs of discrim- 

 ination. They sniff entrances to be sure but far less than the 

 normal rats. Like other rats they take the side paths in the 

 great majority of cases, going from one to the other around the 

 sides of the entrance box or directly across as the case may be. 

 Today they had two trials each and in both trials the true path 

 was the middle path "B." "A" was entered 39 times, "C" 

 29 times, and "B" only nine times. 



July 10. These rats are still slow. They are not "nosing" 

 as much as the other rats, they are just blundering in. 



July 19. This rat, (rat 2) is exploring systematically — 

 "nosing" entrances. 



July 22. Rat " 2 " appears to be learning some way, just how 

 it is difficult to say. She has only made two errors in the last 

 six trials. 



July 27. Rat "2" made one error in five trials. In the 

 second trial she "nosed" the entrances several times over. In 

 the third trial she tried the entrances of C, B, A, B, C, and B, 

 and finally went unhesitatingly down A. In the fifth trial she 

 remained at the entrance to C for a time and then went over 

 to B and down. I have discovered how she does it. She puts 

 her nose over the upper edge of the partition far enough to get 

 contact with her under lip. This contact sensation would be 

 unusually strong when she draws her lip down between the 

 corrugations on the true pathway. This rat was the only one 

 of the group to learn the problem and this was the way she 

 did it. 



This group like the others began w4th a general mode of 

 behavior which resulted in a gradual dropping out of errors, 

 shortening of time, and falling out of the many extraneous 

 activities. But the others from this kind of a reaction developed 

 characteristic discriminative types of action which solved the 

 situation, a thing this group was unable to do. The experiment 

 covered a period from June 11 to Oct. 7, 191 1, and in this time 

 the greatest number of trials for any rat was 441. At the end 

 of the four mori^ths the nerves were regenerating, sensitivity 

 was returning and no doubt the rats would eventually have 

 learned the secret of the box as the normal animals did but it 

 seemed useless to continue the work further. 



The graph which follows (fig. 13,) is made from the totals 



