MENTAL LIFE OF MONKEYS AND APES 63 



the direct choice of the middle box was next to impossible, and 

 Sobke tended to choose, first of all, a particular box toward one 

 end of the series, for example, box 2, in setting 3, and box 7 in 

 setting 9. To the experimenter, as he watched the animal's 

 behavior, it looked as though effort each time were being made 

 to locate the middle member of the group. This appeared 

 relatively easy for groups of three boxes, extremely difficult 

 for as many as five boxes, and almost impossible for seven or 

 nine. 



3. Julius, Pongo pygmaus 

 Problem 1. First at the Left End 



The orang utan, Julius, was gentle, docile, and friendly with 

 the experimenter throughout the period of investigation. He 

 at no time showed inclination to bite and could be handled safely. 

 As contrasted with Skirrl and even with Sobke, he adapted 

 himself to the multiple-choice apparatus very promptly, and 

 only slight effort on the part of the observer was necessary to 

 prepare him, by preliminary trials, for the regular experiments. 

 But in order to facilitate work, he was familiarized with the 

 apparatus by means of regular route training and feeding in 

 the several boxes from April 5 to April 9. 



On April 10 the apparatus was painted white as has been 

 stated previously, and on the following Monday, April 12, 

 Julius when again introduced to it gave no indications of fear, 

 uneasiness, or dislike, but worked as formerly, making his round 

 trips quickly and eagerly entering any box which happened to 

 be open, in order to obtain the reward of food. 



The regular experimentation was undertaken on April 13, 

 and the results of the first series of trials with Julius are sharply 

 contrasted with those obtained with the monkeys in that fewer 

 choices were necessary. Instead of the expected ratio of right to 

 wrong first choices, 1 to 2.5, the orang utan gave a ratio of 1 to 

 1. An additional markedly different result from that obtained 

 with the monkeys is indicated below in the total time required 

 for a series of trials. As examples, the data for the first, second, 

 fifth, and tenth series are presented. 



Time for Series of Trials 



1st series 2nd series 5th series IQth series 



Skirrl 35 min. 20 min. 14 min. 10 min. 



Sobke 14 " 17 " 10 " 9 " {8th series) 



Julius 12 " 11 " 14 " 9 " 



