260 'Journal of Comparative Neurology and Psychology. 



ter than the records indicate. The point at issue, however, is 

 not the rate of learning, but merely the question whether these 

 animals did learn to discriminate two situations in which the pres- 

 ent sense stimuli were identical, namely, two red cards. I set as 

 an arbitrary standard of mastery twenty-five successive perfect 

 responses. More than this was attained with No. i, giving each 

 series once, and again giving each series twice. I attained it for 

 the series of reds with both No. 2 and No. 3, and so nearly attained 

 it with the other series that no doubt remains of their practical 

 mastery of the situation. 



This appears more clearly if we realize that had the animal 

 climbed up at every card of the white-blue-red series, he would 

 have made one hundred mistakes and only fifty correct responses 

 in fifty trials. Yet the animal was very eager to go up on the box. 

 All the food he ever had when colored cards were shown he 

 received at that place. With this chance for mistakes the record 

 seems conclusive. 



Does the method of the experiment warrant the claim that the 

 animal retains an image of the cards which just preceded red ? 

 For No. I, success meant first, that he respond to red preceded 

 by white and blue, now both out of sight, and that he refuse to 

 respond to red preceded by two reds, now both out of sight. Later 

 he must refuse to respond to six reds in succession, but continue 

 the old response to white-blue-red now given twice in succession. 

 Certainly no counting can enter here. The other two learned the 

 alternate order as rapidly as No. I in the light of his previous three- 

 color training. Therefore his work is typical. 



The behavior of all three animals happens to be more conclusive 

 than the records of their learning, for each one, on seeing the first 

 red, would drop down from a position with both forepaws on the 

 front board to stand on all fours on the floor in front of it and 

 merely glance up at the succeeding reds. As soon as the white 

 appeared, however, the animal would lean up against the front 

 board, claw down the white and the blue but never the final red. 

 Moreover he kept his eyes directed on the point at which these colors 

 appeared and promptly clawed them down. Now does not the law 

 of parsimony demand that these reactions be explained as due to 

 visual images with which the animal compared the appearing 

 card ? The turning back and looking for the final color, when the 

 impulse to start up is strong, and the few failures to respond at all, 



