108 CHARLES A. COBURN AND ROBERT M. YERKES 



ratio of 1 to 1.12. But this, after fifty additional trials, is 

 replaced by a ratio of 1 to 7.33. Immediately thereafter, rapid 

 improvement sets in, and shortly a ratio of 1 to 1.15 results. 



The same in general holds for number 4. At the end of fifty 

 trials, its ratio is 1 to 5.25. After one hundred and seventy- 

 seven trials, it is 1 to 1.08. Then the number of correct first 

 choices slowly decreases until finally, at about the three hundredth 

 trial, the ratio is 1 to 11.50. There follows, during the next 

 seventy-five trials, improvement which results in the ratio of 



1 to 1.55, which, in turn, is immediately followed by the ratio 

 of 1 to 5.25. 



These fluctuations in the ratio of right to wrong first choices 

 are indicative of the appearance, "trying out," and disappearance 

 of more or less satisfactory reactive tendencies. The fact that 

 neither bird achieved a ratio of 1 to indicates that no reactive 

 tendency appeared which was wholly satisfactory, or in other 

 words, led to the complete solution of the problem. These 

 various reactive tendencies we should describe, in the case of a 

 human subject, as the "trying out" of ideas, but it is unnecessary 

 for us to have recourse to this mode of psychological description 

 in the case of the crows. They may or may not have had ideas 

 corresponding to those which would have existed in the ordinary 

 human subject. In any event, their behavior is strikingly 

 similar to that of the human subject of a low level of intelligence. 



ANALYSIS OF THE REACTIONS OF CROW NUMBER 3, cT 



An analysis of the data of table 5 renders these fluctuations 

 of the ratio of correct to incorrect first choices at once intelligible 

 and deeply significant. We shall attempt an analytical exam- 

 ination of the results for each subject in order to bring the several 

 reactive types and tendencies into prominence. 



For crow number 3 the first thirty or forty trials in problem 



2 in large measure destroyed the subject's well formed habit 

 of choosing first, as a result of previous training in problem 1, 

 the first compartment at the right. The bird then began to 

 choose very frequently the first compartment at the left and to 

 distribute the remainder of its choices among the other compart- 

 ments, until the right one happened to be chosen. From the 

 beginning of work on this problem, the persistency of number 3, 



