78 FREDERICK S. BREED 



The tests of retention of the black-blue habit after size train- 

 ing, which intervened between the original training and the 

 retention tests, at least suggest a method that may be useful 

 in studies of the interrelation of habits. 



The method of training with the electric shock frequently 

 made the stimulus to which it was attached the emphatic one. 

 In such a case the chicks were not guided in their reactions 

 by the color through which they escaped, but by the color in 

 connection with which they were shocked. That is, the reaction 

 was negative to blue, not positive to black, when this occurred 

 in black-blue training. Psychologically, it seems, negation is 

 not affirmation. 



Of nine chicks perfectly trained in black-blue, five made 

 perfect persistence tests after an interval of thirty days. 



In the case of the same tests of retention, rapidity of modifi- 

 cation was positively correlated with permanence of modification. 



For these nine chicks the " index of modifiability " was 72.2. 



" Trial and error ',' is an unsatisfactory name for this method 

 of learning. 



