MENTAL LIFE OF MONKEYS AND APES 



19 



Problem 4. Middle mechanism of the group 



Total 50 



It was found desirable after a problem had been solved to 

 present a new and radically different series of settings in order 

 to determine to what extent the subject had learned to choose 

 the correct door by memorizing each particular setting. These 

 supplementary observatioijs may be known as control experi- 

 ments, and the settings as supplementary settings. In case of 

 these, as for the original settings, the essential facts are pre- 

 sented in tabular arrangement. 



Settings for Control Experiments 

 Problem 1. First at left end 



