4 are of interest for a number of reasons. In the
first place, the setting 1. 2. 3 appearing twice,--at the beginning of
the series and again at the end--yielded markedly different results in
the two positions. For whereas no mistakes were made in the case of
setting 1, there were fifty per cent of incorrect first choices for
setting 10. Again, satisfactory explanation is impossible. It is
conceivable that fatigue or approaching satiety may have had something
to do with the failures at the end of the series, but as a rule, as is
indicated by settings 1, 2, and 6, if correct choices were made at the
beginning, they continued throughout the day's work.

In this problem, Sobke's improvement was steady and fairly rapid, and in
the eighth series, trials 71 to 80, only correct first choices appear.
Consequently, seventy trials were required for the solution of the
problem. This number is in marked contrast with Skirrl's one hundred and
thirty-two trials.

Immediately following the first perfect series, Sobke was given two
series of control tests on April 28. Conditions were unfavorable, since
the day was stormy and the rain pattering on the sheet-iron roof made a
great din. Nevertheless, he worked steadily and well up to the sixth
trial, which was preceded by a slight delay because of the necessity of
refilling some of the food boxes. After this interruption, wrong choices
occurred in trial 6. And again after trial 9, there was brief
interruption, followed by wrong choices in trial 10. The ratio of right
to wrong choices for this first control series was therefore 1 to .25.

TABLE 4

Results for Sobke, _P. rhesus_, in Problem 1

========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+========
| No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio
Date | of | | | | | | | | | | | R | W | R | W | of
| trials | 1.2.3 | 8.9 | 3.4.5.6.7 | 7.8.9 | 2.3.4.5.6 | 6.7.8 | 5.6.7 | 4.5.6.7.8 | 7.8.9 | 1.2.3 | | | | | R to W
--------+-----------+---------