2. Sobke, _Pithecus rhesus_


_Problem 1. First at the Left End_

Sobke was somewhat afraid of the experimenter when the investigation was
undertaken, and instead of willingly coming out of his cage when the
door was raised, he often had to be coaxed out and lured into the
apparatus with food. Whereas Skirrl was frank and rather aggressive,
Sobke was stealthy in his movements, furtive, and evidently suspicious
of the experimenter as well as of the apparatus. He was perfectly safe
to approach, but would not permit anyone to touch him. After a few days,
he began to take food from the hands of the experimenter.

Preliminary work to acquaint this monkey with the routine of the
experiment was begun on April 13. As in the case of Skirrl, he was lured
into the apparatus and was taught the route through the boxes to the
starting point by being allowed to obtain food once each day in each of
the nine boxes. The procedure was simple. The entrance door and the exit
door of a particular box were raised and the animal admitted to the
reaction-compartment and permitted to pass through the box whose doors
stood open, take its food, and return to the starting point. Sobke very
quickly learned the route perfectly and came to work steadily and
rapidly. After five days of preliminary work of this sort, he was so
thoroughly accustomed to the apparatus that it was evidently desirable
to begin with regular training experiments.