52 ROBERT M. YERKES 



Examination of table 5 indicates that some of the settings 

 proved very easy for Sobke; others, extremely difficult. Con- 

 sequently, the number of methods which were tried and re- 

 jected for a given setting varies from two to five. Setting 2 

 proved a fairly simple one, and after the inhibition of the 

 tendency to choose the first box at the left, the only definite 

 tendency to appear was that of choosing the first box at the 

 right, and then the one next to it. After one hundred and 

 thirty trials, this method suddenly gave place to direct choice 

 of the right box, and during the following twenty-eight series, 

 no error occurred for this setting. Setting 4, on the contrary, 

 proved extremely difficult, and a variety of methods is more 

 or less definitely indicated by the records. 



It is needless to lengthen the description by analyzing the 

 data for each setting, since the reader by carefully scanning the 

 columns of data in table 5 may observe for himself the various 

 tendencies and their mutual relations. 



Sobke's curve of learning (figure 19) in problem 2, is extremely 

 irregular, as was that of Skirrl. Similar irregularities appear 

 in the daily ratios of right to wrong first choices presented in 

 the last column of table 5. Most of these irregularities were 

 due, I have discovered, to unfavorable external conditions. 

 Thus, dark rainy days and disturbing noises outside the labora- 

 tory were obviously conditions of poor work. 



On the day following the final and correct series for problem 

 2, a control series was given. In this Sobke seemed greatly 

 surprised by the new situations which presented themselves. 

 Repeatedly he exhibited impulses to enter the box which would 

 have been the correct one in the regular series of settings. He 

 frequently inhibited such impulses and chose correctly, but at 

 other times he reacted quickly and made mistakes. It was 

 evident from his behavior that he was not guided by anything 

 hke a definite idea of the relation of the right box to the other 

 members of the group. 



In a second control series given on the following day, June 12, 

 confusion appeared, but less markedly. For the first setting, 

 a correct choice was made with deliberation. For the second 

 setting, box 3 was immediately chosen, as should have been the 

 case in the regular series of settings. Sobke seemed confused 

 when he emerged from this box and had difficulty in locating 



