98 ROBERT M. YERKES 



It is especially important, in connection with these results, 

 to point out the risk of misinterpretation of observations on the 

 anthropoid apes. If they can imitate human activities as readily 

 and effectively as Julius did in this particular experiment, we 

 can never be sure of the spontaneity of their ideational behavior 

 unless we definitely know that they have had no opportunity 

 to see human beings perform similar acts. 



Of all the methods of eliciting ideational or allied forms of 

 behavior used in my study of the monkeys and ape, none yielded 

 such illuminating results as the box stacking test, and although 

 from the technical standpoint, it has many shortcomings, as a 

 means to qualitative results it has proved invaluable. 



Other Methods of Obtaining the Reward 



Some weeks later, I tried to discover how Julius would obtain 

 the much desired banana when the boxes were absent. I placed 

 in the large cage a stick about six feet long and an old broom. 

 When admitted, he looked about for the boxes, but not seeing 

 them, picked up the broom and placing it with the splints down, 

 beneath the banana, he tried to climb it, but as it fell over with 

 him, he abandoned this after a few trials, went to his cage, 

 and picking up some old bags which he used at night as covers, 

 he dragged them out and placed them on the floor beneath the 

 banana. He next put the broom upon them and tried to climb 

 up. This general type of behavior persisted for several min- 

 utes, everything within reach being used as were the bags, as 

 a means of raising him in the desired direction. Finally, he 

 placed his feet on the broom where the handle joins the splints, 

 seized the handle near the top with his hands, drew himself up 

 as far as possible, and then launched himself in the air and 

 tried to seize the banana. On the third attempt he succeeded. 



Later, he was given a plain stick about five feet long. Figure 

 32 of plate VI shows him using this to obtain the banana in 

 the manner described above. He would grasp it with one or 

 both feet, usually one, ten to fifteen inches from the floor of 

 the cage, meanwhile holding with his hands near the top of 

 the stick. He would then, with all his strength, draw himself 

 up suddenly and jump toward the banana. Often he came down 

 rather hard on the cement floor, much to his disgust. 



Yet another rdethod of obtaining the reward developed a day 



