JOURNAL OF AN IMAL BEHAVIOR 



Vol. 6 JULY-AUGUST No. 4 



COMPARISON OF THE BEHAVIOR OF STOCK AND 

 INBRED ALBINO RATS 



ADA W. YERKES 



The Psychological Laboratory of Harvard University 



For a number of years the Wistar Institute of Anatomy and 

 Biology has been carrying on experiments in inbreeding the 

 albino rat, Mus Norvegicus albinus, for the purpose of studying 

 the anatomical effects of such procedure. In October, 1911, 

 some of the rats, which had then been inbred to the sixth gen- 

 eration, were sent to the Johns Hopkins University and were 

 used by Doctor Basset 1 for comparative studies in habit 

 formation. 



In April, 1913, while Basset's experiments were still in pro- 

 gress, the suggestion of similar cooperation in the study of 

 the effects of inbreeding on the formation of habits was made 

 by the Wistar Institute to the Harvard Psychological Labora- 

 tory and gladly accepted. It was then so late in the collegiate 

 year that only a few preliminary experiments were made at that 

 time by Professor Yerkes and two students, using the method 

 of brightness discrimination. The following October the writer 

 undertook, at Professor Yerkes' suggestion, 2 a study of certain 



1 Basset, G. C. Habit formation in a strain of albino rats of less than normal 

 brain weight. Behavior Monographs, 1914, vol. 2, no. 4. 



2 In suggesting to Mrs. Yerkes a comparative study of stock and inbred rats, 

 I expressed especial interest in the attempt to analyze "the temperament" of the 

 animals, for certain previous observations in comparison with those reported by 

 Basset had convinced me that crude measurements of modifiability, if directly 

 compared, might lead to seriously misleading conclusions because of differences 

 in timidity, savageness, aggressiveness, sensibility, etc., in the two groups of organ- 

 isms under observation. 



Mrs. Yerkes' work, unfortunately, was seriously interfered with by unexpected 

 difficulties in the breeding of rats in the new Harvard Laboratory of Animal Psy- 

 chology. From the statistical standpoint, her results are unsatisfactory because 

 of this difficulty. 



