22 FREDERICK S. BREED 



the cause was usually the refusal of the chick to eat. This 

 difficulty was soon obviated by carefully controlling the amount 

 of food allowed the chicks, and compelling them to scratch for 

 it in the litter. The objection also was thereby forestalled that 

 many chicks under an improperly regulated food supply might 

 react the required number of times but below their highest 

 efficiency. 



Not only did these difficulties threaten to affect the reliability 

 of the results, but an additional reaction came in to complicate 

 the record. When the food supply was improperly controlled, 

 the chicks would quite often reject grains, that is, lift them from 

 the ground with the bill and then either drop them or throw 

 them some distance without attempt to recover. Forcible rejec- 

 tion is distinctly a reaction in addition to reaction 3. It involves 

 control of the grain by the mandibles — sufficient, one should 

 suppose, for manipulation without error prior to swallowing. 

 If this be true, it is manifestly unfair to charge the chick with 

 a degree of imperfection by recording reaction 2. Yet, one is 

 not at liberty to credit it with reaction 4. A clear instance of 

 rejection should simply not figure in the records. But this 

 disturbing feature was practically eliminated when the chicks 

 were confined in the brooder at night and were given the proper 

 amount of food only after the morning tests. I say practically 

 eliminated, because, even after taking the precaution men- 

 tioned, some chicks in time came to eat one kind of grain and 

 not another. For example, I have found an occasional chick 

 that discriminated in this fashion between millet seeds with 

 the shell on and those without the shell, to say nothing of prefer- 

 ences for wheat as against com, millet as against wheat, and 

 the like. In such cases the chick was fed what it readily ate. 



Another variation, which we may term switching of the biU, 

 occasionally appeared. It is similar in character to the forcible- 

 rejecting movement, and was observed in some very young 

 chicks. It is executed while the food particle is held firmly 

 between the mandibles. It is mentioned here rather as an 

 additional type of reaction than as a source of error, for it did 

 not noticeably affect the records. 



I have so many times observed chicks, especially very young 

 ones, peck where I could see nothing but bare wood or card- 

 board, that I am compelled to believe that the stimulus to the 



