52 

 is this true when hunger is a stimulus, //hen this is 



properly controlled, it is one of the best for evoking 

 responses. Too little or too much food defeats results 

 desired. It is a great mist aire to reduce the amount of 

 the food in order to increase the activity of the animal. 

 This is especially harmful in the early trials when primal 

 movements are made and their organization is taking place. 



nimal may miss making a favorable movement that it 

 might have made if there had been better bodily tone. 

 Oftentimes, it appears, that it is the control of the a- 

 mount of food which hastens learning. When attention 

 is paid to food regulation a fcaximum of effort is ob- 

 tained without disturbance to metabolism. 



Because of the disturbances to metabolism and the 

 supposed unnaturalness of hunger as a stimulus, objec- 

 tions have been raised against it, and punishment or some 

 other stimulus has been preferred. This objection is 

 not well founded. Of all the stimuli used, hunger seems 



