The evidence suggests that in this young orang utan ideational learning tended to replace the simpler mode of problem solution by trial and error.  Seemingly incapable of solving his problems by the lower grade process, he strove persistently, and often vainly, to gain insight.  He used ideas ineffectively.  Animals far lower in intelligence (e.g., the pig), surpass him in ability to solve these relational problems because they use the method of elimination by trial consistently and effectively.  Julius, in these experiments, made a poor showing because his substitute for trial and error is only slightly developed.  Would he have succeeded better with the same problems if mentally mature?

There are many important features of the results which, for lack of space, have not been indicated or discussed.  They can be developed from later comparative studies of the data, for in the tables appear all of the essential facts of response apart from those mentioned in the text.

IV

RESULTS OF SUPPLEMENTARY TESTS OF IDEATIONAL BEHAVIOR

1.  Julius, Pongo pygmaeus

Box Stacking Experiment

In addition to the multiple-choice experiments which have been described in detail in the previous section, it was possible to conduct certain less systematic tests of ideational behavior in the monkeys and the orang utan.  From the technical standpoint these tests were relatively unsatisfactory because only inexactly describable.  But their results are in many respects more interesting, if not also more important, in the light which they throw on ideation than are those previously presented.  First, in order of time, comes a test which may be designated as the box stacking experiment.  The method will now be described in connection with an account of the behavior of Julius as contrasted with that of a child of three years and four months of age.

In the large central cage labelled Z, figure 12, which was twenty-four feet long, ten feet wide, and ten to twelve feet deep, the following situation was arranged.  From the center of the wire covering of the cage, a banana was suspended on a string so that it was approximately six feet from the floor, five feet from either side of the cage, and twelve feet from either end.  From all approaches it was far beyond the reach of Julius, since it was impossible for him to climb along the wire roof and thus reach the string.  Two boxes were placed on the floor of the cage several feet from the point directly under the banana.  The one of these boxes was heavy and irregular in shape, as is shown in figures 21, 23 and 24 of plate V. Its greatest height was twenty-one inches; its least height, eighteen inches; its other dimensions, twelve and sixteen inches respectively.  The smaller and lighter box measured twenty-two by twelve by ten inches.  According to the experimenter’s calculations, the only way in which Julius could obtain the banana was by placing the smaller box upon the larger and then climbing upon them.