inclination to timidity or nervousness even in the presence of
conditions not in themselves startling.

Work was continued thus steadily until May 28 when, because of the
failure of the animal to improve, it seemed wise to increase the period
of confinement as punishment to sixty seconds. In the meantime, it had
sometimes been evident that Sobke was near to the solution of his
problem. He would often make correct choices in three or four trials in
succession and then apparently lose his cue and fail utterly for a
number of trials.

After June 1, in order to hasten the solution of the problem, two series
per day were given. In some instances the second series was given almost
immediately after the first, while in others an interval of an hour or
more intervened. It was further found desirable to give Sobke all of his
food in the apparatus. When the rewards obtained in the several trials
did not satisfy his hunger, additional food was presented, on the
completion of the series of experiments, in one or more of the food
cups. On days marked by unwillingness or refusal to work, very little
food was given. Thus, the eagerness of the monkey to locate the right
box was increased and, as a matter of observation, his deliberateness
and care in choice increased correspondingly. Sixty seconds punishment
was found satisfactory, and it was therefore continued throughout the
work on this problem.

It was evident, on June 9, from the behavior of the monkey as well as
from the score, that the perfect solution of the problem was near at
hand. This fact the experimenter recorded in his daily notes, and sure
enough, on the following day Sobke chose correctly throughout the series
of ten trials. The time for this series was only ten minutes. The