One day as Skirrl was being returned to his own cage by way of the larger cage, he picked up an unfastened padlock and carried it into the cage with him.  For more than an hour he amused himself almost without interruption by playing with this lock.  The things which he did with it during that time would require pages to describe.  His interest in it was very similar to that which he had exhibited in hammer and nails, saw, and indeed any objects which he could play with.  The lock was pounded in various ways, bitten, poked with nails, hooked into the wires of the cage, used to pull on, pounded with a stick, used to hammer on the floor of the cage with, and in fine, manipulated in quite as great a variety of ways as a human being could have discovered.  Finally it was hooked to the side of the cage and snapped shut, and as Skirrl was unable to dislodge it from this position, he shortly gave up playing with it.

At the end of the large cage and just outside the wire netting was a faucet to which a hose was usually attached.  The valve could be opened by turning a wheel-shaped hand piece.  Both Skirrl and Julius learned to turn this wheel in order to get water to play with, but usually the former’s strength was not sufficient to turn on the water.  The latter could do it readily.  The indications are that both animals profited by seeing human beings turn on the water.  This unquestionably attracted their attention to the faucet, and probably by playing with it they accidentally happened upon the proper movement.  At any rate, Skirrl’s behavior was significant in this connection, for he would pick up the hose to see if water were flowing, and if it were not, he would throw it down, go directly to the faucet, and try to turn the wheel.  The association of the wheel with the desired flow of water was therefore definitely established.  Shall we describe the act as ideational?  It seems the natural thing to do.

3.  Sobke, Pithecus rhesus

Box Stacking Experiment

For this test, in the case of Sobke, three light boxes made of redwood about one-third of an inch thick were used.  The smallest, box 1, was six inches in each direction, the next larger, box 2, was twelve inches, and the third, box 3, eighteen inches.  As in the case of the other animals, bait, either banana or carrot, was suspended from the middle of the roof of the large cage at such distance from the floor as to be reached by the animal only by the use of the boxes.

The first observations on Sobke were made on June 14.  The three boxes had been placed in the form of a pyramid directly under the banana, which hung about eighteen inches above the uppermost box.  Sobke’s attention while in his cage had been attracted to the bait by seeing me fastening it in position, but when admitted to the large cage, he simply glanced at it and then wandered about the cage, picking up bits of food and struggling to get at the other monkeys.  This he did for about five minutes.  He then went to the boxes, placed his hands on top of the bottom one, but did not climb up on it.  A few minutes later he returned to the box again, climbed up, and readily reached the food, which he ate while resting on boxes 1 and 2.