Sobke made ten correct first choices in the third series for July 17,
but he was working very uncertainly and it seemed rather a matter of
good luck than good management that he succeeded in presenting this
perfect series: For this reason and also because it did not seem
feasible to have Sunday intervene between the final and perfect regular
series and the control series, an additional regular series was given on
July 19, in which, as the table indicates, a single mistake occurred, in
trial 5. The monkey was working perfectly. The series of trials required
only ten minutes, and it was evident that carelessness and eagerness to
obtain food were chiefly responsible for the mistake.

The control series given on July 19 immediately after the series just
described resulted similarly in one failure and nine successes. The
choices were made easily and with certainty, and the only mistake, that
of setting 7, was apparently due to carelessness.

This excellent showing for the control series wholly justifies the
comparison of problems 2 and 3 as to difficultness, made above. Whereas
in both problems 1 and 2 the control trials caused confusion, in the
case of problem 3, they did not essentially alter the behavior of the
animal. The fact seems to be that for this problem the particular
setting is of relatively little importance; while turning alternately to
the extreme left and the extreme right is of prime importance. That
Sobke had the idea of alternation or of the end box, there seems no more
reason for insisting than that he had the idea of secondness from the
right end in problem 2. It is possible, even probable, that these ideas
existed rather vaguely in his consciousness, but there is obviously no
necessity for insisting that the solution of the problems depended upon
them.