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This eBook from the Gutenberg Project consists of approximately 205 pages of information about The Mental Life of Monkeys and Apes.
to avoid the general region in which success was never obtained and to focus attention on the right, as contrasted with the wrong end of each group. It obviously contradicts the law of the gradual elimination of use less activities. In other words, it is wholly at variance with the principle of trial and error exhibited by many infrahuman organisms.  Julius, although making many mistakes, worked diligently and, for the most part, fairly rapidly.  The day’s work proved most important because of the change in method and also because of the appearance of hesitation, the rejection of certain boxes, and the definite choice of others.  My notes record “this is a most important day for Julius in problem 2;” but subsequent results do not clearly justify this prophecy.

The method of choosing the first box at the left and then of moving down the line until the right one was reached was so consistently followed that during a number of days it was possible for me to predict almost every choice.  Indeed, to satisfy my curiosity in this matter during a number of series I guessed in advance the box which would be chosen.  The percentages of correct guesses ranged from ninety to one hundred.  June 10, for example, yielded two series for which the ratio of right to wrong first choices was 0 to 10, and in which the method described above was used consistently throughout.

It was inevitable that punishment by confinement and the discouragement resulting therefrom should interfere with the regularity of work and make it extremely difficult to obtain strictly comparable results from series to series and from day to day.  The data for this problem, as presented in table 9, have values quite different from those for the monkeys, chiefly because of the more variable conditions of observation.

It was occasionally noted that the disintegration of a definite method and the disappearance of the tendency on which it depended occurred rather suddenly.  Frequently it happened that having used an inadequate method fairly persistently on a given day, the animal would on the following day exhibit a wholly different method.  Even over night a new method might develop.  In the monkeys, although there was occasionally something comparable with this, it was by no means so evident.

TABLE 9

Results for Orang utan in Problem 2

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