MENTAL LIFE OF MONKEYS AND APES 65 



the two methods were again employed, the first in the initial 

 series and the second in a final series of trials. The animal's 

 persistent attempts to raise the doors gave the experimenter 

 so much trouble that on April 29 barbed wire was nailed over 

 the windows of the entrance doors with the hope that it might 

 prevent him from working at them. But he quickly learned to 

 place his fingers between the barbs and raise the doors as effec- 

 tively as ever. 



On April 30 the rew^ard of food was given only when the first 

 choice was that of the right box and in that event it was placed 

 in the alleyway H as stated above. 



As it seemed absolutel^^ essential to break the unprofitable 

 habit of choosing the nearest door, on May 3 a new series of 

 settings was presented, in which only the doors to the left of 

 the middle of the row of nine boxes were used as right doors. 

 That is, in this new series, doors 1 to 4 occur as right doors; 5 

 to 9 do not. As punishment for wTong choices on this date, 

 Julius was confined in the wrong box from one to five minutes. 

 It was difficult to keep him in, but by means of cords which had 

 been attached to the doors, this was successfully accomplished. 

 Yet another and slightly different series of settings was employed 

 on May 4, and this, proving satisfactory, was continued in use 

 until the end of the experiment, with punishment ranging from 

 sixty to one hundred and twenty seconds for each mistake. 



Naturally the modification of settings introduced May 3 

 greatly increased the proportion of wrong first choices. Indeed, 

 as appears in table 8, the ratio of right to wrong immediately 

 changed from 1 :.67 to 1 :4.00. Between May 3 and May 10, 

 no steady and consistent improvem.ent in method or in the 

 number of correct first choices occurred, and on the last named 

 date, Julius chose correctly only three times in his ten trials. 

 At this time there was, as my notes record, no satisfactory indi- 

 cation of progress, and the status of the experiment seemed ex- 

 tremely unsatisfactory in as much as in spite of the experimenter's 

 best efforts to break up the habit of choosing the nearest door, 

 the orang utan still persisted, to a considerable extent, in the 

 use of this method. The only encouraging feature of the results 

 was an evident tendency to choose somewhat nearer the left end 

 of a group than previously. 



A series of correct first choices was obtained on May 11, 



