A STUDY OF THE BEHAVIOR OF THE CROW 



107 



In table 7 the ratios of correct to incorrect first choices are 

 given for the trials by groups of twenty-five, in order that the 

 influence of "good" and "bad" days may be fairly distributed. 



The probability of a correct choice in this experiment, supposing 

 that chance alone is involved 5 , is one to four. At the beginning 

 of the experiment, it is noted (table 7) that the ratio for number 

 3 was 1 to 7.30; that for number 4, 1 to 5.25. For neither bird 

 does the ratio fall as low as 1 to 1 at any time during the training. 

 The nearest approach to this measure of success was made by 

 crow number 4 in the trials 153 to 177, for which the ratio was 

 1 to 1.08. 



Further, it is to be noted that neither crow shows a steady 



increase in the number of correct choices. There is, instead, 



for each, an increase up to a certain point, then a sudden decrease, 



followed by a more or less rapid increase. Number 3 exhibits 



three well marked improvement waves. Beginning with the 



ratio 1 to 7.3, there is fairly constant improvement until the ratio 



stands 1 to 2. Then a backsliding occurs which, for the next 



twenty-five trials results in a ratio of 1 to 5.25. Slowly the bird 



improves again, achieving, after about three hundred trials, a 



5 Of course the previous work on Problem 1 influenced the birds very markedly 

 in their early trials. 



