VISUAL PERCEPTION OF THE CHICK 39 



animal problem depends upon the adoption of a favorable 

 method. The experimenter must use an apparatus by means 

 of which he can accurately control the conditions of his study. 

 He must also show alertness by controlling these conditions in 

 such a way that his animals behave normally. Much animal 

 stupidity, so-called, is really a reflection of human ignorance. 

 The experimenter may lack animal intelligence by setting human 

 problems for a lower animal to solve. 



An animal frequently shows ingenuity in an unexpected direc- 

 tion, and if the experimenter be not alert he misses the most 

 important part of the behavior. How many times this is the 

 case, we cannot tell, for we only know of the cases where we did 

 not miss the significant fact. A perfect method would make it 

 impossible for the animal to pick up cues that were not inten- 

 tionally offered by the experimenter. But it is through experi- 

 ence that we approach a perfect method, because there is always 

 the possibility of improvement even in the best standardized 

 methods. 



The importance of method was impressed upon me through 

 an incident in my experiments with the first group of chicks. 

 I had inexcusably blundered by making the original conditions 

 of discrimination too difficult for the chicks. They were being 



tested on o 28 H © 7 -f discrimination. The subjects were 



allowed to go through the discrimination chamber and experi- 

 ment box during the preliminary tests without regard to the 

 position of the right or wrong stimulus; that is, both exits were 

 open. When the training series were begun the brightnesses 

 of the two stimuli were made markedly unequal and were irreg- 

 ularly varied from the first. 



The experiment was begun with six subjects. As a partial 

 result of my initial bungling, I had at the end of a few days only 

 subjects 2 and 3 in suitable condition for further work. At the 

 end of two and one-half weeks No. 2 gave up, but No. 3 persisted. 

 At the end of the 24th series it had successively made three 

 perfect series (see table 2). At the end of four more series it 



had reacted perfectly to the o 28 -\ o 9 -f- discrimination. 



The diameter of the variable was successively increased by 5 

 mm. until the variable o 19 -F was reached after which the diam- 

 eter of the variable was changed by increments of 1 mm. 

 The perfect responses continued with very few exceptions. 



