MENTAL LIFE OF MONKEYS AND APES 39 



were made in box 8, which, as it happened, had proved a 

 peculiarly easy one for him throughout the training, since from 

 the first he tended to avoid door 9. Consequently, it is only 

 fair to conclude, from the results for this control series and for 

 those given on August 11 and 12, that the animal chose not on 

 the basis of anything remotely resembling a general idea of 

 secondness from the right end, but instead on the basis of gradu- 

 ally acquired modes of reaction to the particular settings. This 

 conclusion is strengthened by the fact that he had failed to 

 learn to react appropriately and readily to most of the settings 

 of the regular series. 



The curve which represents the course of the learning process 

 in this problem is presented in figure 19. For this and all other 

 curves which involve more than a single series of observations 

 a day, the method of construction was as follows : The first series 

 for each day of training is indicated on the curve by a dot, while 

 the second or third series on a given day, although space is allowed 

 for them, are not so indicated. Consequently, the form of the 

 curve is determined chiefly by the first series per day. The ex- 

 treme irregularities of this curve are most interesting and puzzl- 

 ing, as are also the variations in the daily ratios of right to wrong 

 first choices. Three times in the course of the training, this ratio 

 rose to 1 to 9, or higher. The causes for such extreme varia- 

 tions are not easily enumerated, but a few of the most obvious 

 contributory causes are variations in the weather, especially 

 cloudiness or fogginess, which rendered the apparatus dark; 

 variations in the degree of hunger or eagerness for food; differ- 

 ences in the activities of the animals in the cages outside of the 

 laboratory (sometimes they were noisy and distracted the sub- 

 ject), and finally, differences in the physical fitness and attitude 

 of the animal from day to day. 



The more or less incidental behavior in connection with this 

 experiment more strongly than the statistical results of the work 

 on problem 2 indicate the existence of imagery. That ideas 

 played a part in the solution of the problem is probable, but 

 at best they functioned very ineffectively. The small number 

 of methods used in the selection of the right box, and the slight 

 variations from the chief method, that of choosing the first box 

 at the right end and then the one next to it, apparently justify 

 Doctor Hamilton's characterization of this monkev as defective. 



