298 HARVEY CARR 



and one which we may term a defective because of the loss of 

 considerable cerebral tissue. 



The learning records of this group of animals present many 

 interesting features. The blind animal mastered the maze in 

 24 trials with a total error score of 152. After this time, the 

 rat ran the maze consistently without error. This record is > 

 similar to those for blind and normal animals. Those two that 

 were blind, and anosmic on the left side gave poorer records; 

 one required 52 trials and 144 errors, and the second 102 trials 

 and 508 errors. After the maze was mastered according to the 

 criterion used, many errors kept appearing in an irregular man- 

 ner for 25 to 40 trials. The blind and anosmic animal did still 

 poorer; it required 130 trials and 2582 errors to learn this maze, 

 but the act did not become thoroughly automatic until the 

 200th trial. It was also necessary to help this rat in 76 trials 

 while learning the maze. In the early trials this animal utterly 

 failed to reach the food box after several hours of effort and an 

 error score of over 100. After the animal became exhausted I 

 would stimulate it to further efforts and guide it when necessary. 

 After the twentieth run I aided the rat whenever it became 

 apparent that it was hopelessly lost. The defective rat required 

 194 trials and 1855 errors to master the maze. It was also 

 helped in 32 of its trials. The act did not become thoroughly 

 automatized for some time after the maze was considered learned. 

 These results are significant because the difficulty of mastery 

 is proportional to the degree of olfactory deficiency. The loss 

 of either smell or vision does not operate as a detriment to the 

 mastery of the maze; the loss of vision together with the partial 

 or total destruction of smell is exceedingly detrimental. Evidently 

 the deficiency due to the absence of either vision or smell is com- 

 pensated in some manner by the other sense, while the remaining 

 senses are unable to compensate for the deficiencies of both. 



Rotation of the heterogeneous environment produced little dis- 

 turbance upon the blind and anosmic or upon those which were 

 blind and partially anosmic. The average error records for six 

 trials were .33 and .66 respectively. The error record of the 

 defective animal was 2.33. The normals gave a score of 1.90, 

 the blinds 2.32, and the anosmics 2.50. Evidently the loss of 

 both senses minimizes or practically abolishes the rat's sensitivity 

 to these changes. 



