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
--------+-----------+--------------+--------------+---------

-----+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+--------
April  |           |              |              |              |              |              |              |              |              |              |              |   |   |   |   |
19   |    1-10   | 1            | 8            | 3            | 9.7          | 6.2          | 6            | 7.5          | 4            | 9.7          | 1            | 6 | 4 | 6 | 4 | 1:0.67
20   |   11-20   | 1            | 8            | 3            | 7            | 2            | 6            | 7.5          | 8.4          | 9.9.7        | 1            | 7 | 3 | 7 | 3 | 1:0.43
21   |   21-30   | 1            | 8            | 4.3          | 9.7          | 2            | 6            | 5            | 8.4          | 7            | 1            | 7 | 3 | 7 | 3 | 1:0.43
22   |   31-40   | 1            | 8            | 3            | 7            | 6.2          | 6            | 6.5          | 4            | 7            | 3.1          | 7 | 3 | 7 | 3 | 1:0.43
23   |   41-50   | 1            | 8            | 3            | 7            | 2            | 6            | 5            | 4            | 9.7          | 3.1          | 8 | 2 | 8 | 2 | 1:0.25
24   |   51-60   | 1            | 8            | 3            | 9.7          | 2            | 6            | 5            | 4            | 7            | 2.1          | 8 | 2 | 8 | 2 | 1:0.25