MENTAL LIFE OF MONKEYS AND APES 97 



not go up. with the box (according to his expectation?), he aban- 

 doned this method, and looking about, discovered the larger 

 box in a distant corner. Thereupon, he promptly pulled the 

 boxes to their proper position beneath the banana, stacked them, 

 and obtained his food. 



After considerable skill had been acquired in the placing of 

 the boxes, the one upon the other, the height of the banana 

 above the floor was increased so that three boxes were neces- 

 sary. Figure 25 of plate V shows him standing on three boxes 

 and reaching upward, and figures 22, 27 and 28 show various 

 modes of handling the boxes and of reaching from them. He 

 was not at all particular as to the stability of his perch, and 

 often mounted the boxes when it seemed to the experimenter 

 inevitable that they should topple over and precipitate him to 

 the floor. Only once, however, during the several days of 

 experimentation did he thus fall. 



Obviously important is the evident change in the animal's 

 attention on April 20. He watched with a keenness of interest 

 which betokened a dawning idea. Before he had succeeded in 

 stacking the boxes, I had written in my note-book, " He seemed 

 much interested today, in my placing of the boxes. " Interest- 

 ing, and important also, is the ease and efficiency with which 

 he met the situation time after time, after this first success. 

 " Trial and error " had no obvious part in the development of 

 the really essential features of the behavior. The ape had the 

 idea and upon it depended for guidance. 



Except for the fact that Julius was immature, probably under 

 five years of age, it is likely that he would have stacked the 

 boxes spontaneously instead of by suggestion from the experi- 

 menter or imitatively. 



No unprejudiced psychologist would be likely to interpret the 

 activities of the orang utan in the box-stacking experiment as 

 other than imaginal or ideational. He went directly, and in the 

 most business-like way from point to point, from method to 

 method, trying in turn and more or less persistently or repeat- 

 edly, almost all of the possible ways of obtaining the coveted 

 food. The fact that he did not happen upon the only certain 

 road to success is surprising indeed in view of the many ineffec- 

 tive methods which he used. It seemed almost as though he 

 avoided the easv method. 



