A STUDY OF THE BEHAVIOR OF THE CROW 95 



For these ten settings the total number of doors open is fifty, 

 of which ten are "right doors." The chance of a correct first 

 choice, without previous experience or the prejudical influence 

 of training in problem 1, is one to four. 



In this problem, the first fifty trials were given to the crows 

 in groups of two and three each. The birds made so many 

 mistakes at the beginning that they became discouraged, and 

 after two or three trials, would refuse to work. Later, as they 

 became accustomed to the situation and the experimenter 

 increased the degree of hunger, they could be induced to react 

 five times in succession. Consequently the number of trials 

 per series was increased to five. 



Now, as in the case of problem 1 , the experimenter was forced, 

 in order to avoid the possibility of utterly discouraging his 

 subjects, to aid them after they had worked for several minutes 

 without success in locating the right door. This was always 

 done by slightly moving the exit door of the right compartment. 



After sixty-one trials had been given, the period of punishment 

 was increased from fifteen seconds to thirty seconds. The 

 thirty-second interval was used up to the four hundred and 

 sixtieth trial. It was then increased to sixty seconds, but as 

 the crows refused to work, it was decreased after forty trials 

 to fifteen seconds. 



After the fiftieth trial, the series regularly consisted of five 

 trials, and four series were, as a rule, given each day. 



Table 5 presents for problem 2, as does table 1 for problem 1, 

 a summary of the choices for each of five hundred trials given 

 each crow. As in table 1, the settings are indicated at the top 

 of the various columns, and under each setting appear the results 

 of the various trials for that particular setting. 



It appears from table 5 that number 3, in the case of setting 

 No. 1, 7-9, failed with few exceptions in its first choices until 

 the three hundred and forty- third trial, whereas thereafter it 

 usually succeeded. On the contrary, in the case of setting No. 

 6, 5-9, we observe that the bird almost never succeeded in selecting 

 the right compartment in the first trial. Moreover, there is 

 absolutely no evidence of improvement. 



