ABSTRACT
When a chimpanzee cannot reach an objective hung high up with one box, there is a possibility that he will pile two or more boxes on top of one another and reach it in that way. But if experiments are made, it is quickly seen that the problem for the chimpanzee falls into two very distinct parts: one of which he can settle with ease, whilst the other presents considerable difficulties. The chimpanzee is not simply provided for life with any special disposition which will help him to attain objects placed high up, by heaping up any building material, and yet he can accomplish this much by his own efforts and when the material is available. Adult human beings are inclined to overlook the chimpanzee's real difficulty in such construction, because they assume that adding a second piece of building material to the first is only a repetition of the placing of the first one on the ground.
