The results of this experiment indicate the lack in the monkey of any tendency or ability, apart from training, to use objects as means of obtaining food.  Ways of using objects as tools which apparently are perfectly natural to the anthropoid apes and to man are rarely employed by the lower primates.

Hammer and Nail Test

One day I happened to observe Skirrl playing with a staple in his cage.  He had found it on the floor where it had fallen and was intently prodding himself with the sharp points, apparently enjoying the unusual sensations which he got from sticking the staple into the skin in various portions of his body, and especially into the prepuce.

A few days later I saw him playing in similar fashion with a nail which he had found, and still later he was seen to be using a stick to pound the nail with.  This suggested to me the hammer and nail test.

A heavy spike was driven into an old hammer to serve as an indestructible handle.  This hammer, along with a number of large wire nails and a piece of redwood board, was then placed in the monkey’s cage.  Skirrl immediately took up the hammer, grasping the middle of the handle with his left hand, and with his right hand taking up a nail.  He then sat down on the board, examined the nail, placed the pointed end on the board, and with well directed strokes by the use of the head of the hammer drove the nail into the board for the distance of at least an inch.  He then tried to pull it out, but was forced to knock it several times with the hammer before he could do so.

This performance, during the next few minutes, was repeated several times with variations.  Often the side of the hammer was used instead of the head, and occasionally, as is shown in figure 8 of plate II, he seized the hammer well up toward the juncture of the same with the spike.  This figure does justice to the performance.  At the moment the picture was taken, Skirrl’s attention had been attracted by a monkey in an adjoining cage, and he had momentarily looked up from his task, the while holding nail and hammer perfectly still.

This test was repeated on various days, and almost uniformly Skirrl showed intense interest in hammer and nails and used them more or less persistently in the manner described.  Occasionally, apparently for the sake of variety, he would put the blunt end of the nail on the board and hammer on the point.  Again, he would try persistently to drive the nail into the cement floor, and once by accident, when hammer and nails were left in his cage over night, he succeeded in making several holes in the bottom of his sheet iron water pan.  There was no doubting the keen satisfaction which the animal took in this form of activity.