the instinctive fear of snakes, so
strong in monkeys, was partly responsible for his response.

The first result of this accident was that more than two weeks were
lost, for it was impossible, during the next few days, to induce the
animal to enter any of the multiple-choice boxes voluntarily. From May
14 to May 24, I labored daily to overcome his newly acquired fear. The
usual procedure was to coax him through one box after another by
standing at the exit door with some tempting morsel of food. After
several days of this treatment, he again trusted himself to the boxes,
although very circumspectly and only when both entrance and exit doors
were raised. Not until May 24 was it possible to resume regular
experimentation, and on that day it was found necessary to indicate the
right box by raising the exit door slightly and then immediately
lowering it. Trials in which this form of aid was given are indicated in
table 2 by a star following the last choice.

Gradually, Skirrl regained his confidence in the apparatus and began to
work more naturally. For a long time he would not stand punishment, and
it was necessary for the experimenter to be very careful in locking the
doors, since the sound of the bar sliding beneath the floor often
frightened and caused him to quit work. Day after day the tendency to
peer through the holes in the floor at the entrance to the boxes
rendered it clear that the animal feared some danger from beneath the
floor. This behavior was so persistent that much time was wasted in the
experiments.

On the last day of May, punishment by confinement for ten seconds in
wrong boxes was introduced, but since this tended to discourage the
monkey, there was substituted for it on June 1 the punishment of forcing
him to work his way out of each wrong box by raising the entrance door
which had been closed behind him. This he could fairly readily do, and
his stay in a box rarely measured more than ten seconds.

As a variation in the mode of procedure, confinement for thirty seconds
was tried on June 5, but it worked unsatisfactorily and had to be
abandoned. During this series, the animal was startled by the sound from
one of the sliding bars under the floor, and in the sixth trial he
refused to work.

As improvement was very slow, varied modes of rewarding and punishing
the animal were tried in the hope of discovering a means of facilitating
the work. Among the former are the use of banana, grapes, peanuts,