er box into the air. This he did three or four times one day,
raising it toward the banana each time as though he expected thus to
obtain the reward. As he did not go up with the box (according to his
expectation?), he abandoned 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 necessary. 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." Interesting, 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 experimenter 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 repeatedly, 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 ineffective
methods which he used. It seemed almost as though he avoided the easy
method.

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