REWARD AND PUNISHMENT IN HABIT FORMATION 265 



The sensation of hunger was almost constant after the first day of 

 starvation somewhat more severe during the first two or three days. 

 The most severe sensations were at periods of gastric contractions. 

 Appetite ran practically parallel with sensation of hunger. It increased 

 during the first two or three days and diminished on the fourth and fifth 

 days. Instead of an eagerness for food there was an almost indifference 

 to food despite the persistent hunger call of the empty stomach. 



The writer could not give a more exact description of the 

 behavior of these rats after forty-eight hours of hunger than the 

 above. As the average time of choosing indicates, this group of 

 subjects was slightly more active than the group which was 

 trained with twenty-four hours of hunger but they were not eager 

 for food. Still their behavior was indicative of some disturbing 

 factor: they assumed the hump of a starving animal. They 

 largely abandoned it immediately after eating but assumed it 

 again as the hunger period advanced. This disturbing element 

 was due, no doubt, to the continued contractions of the empty 

 stomach. It seems probable from Dr. Carlson's description of 

 his sensations during a starving period, that these rats had sen- 

 sations of hunger but were not eager for food. As may be seen 

 from next to the last column, table 7, and from the curve of 

 learning representing this column, this disturbing factor was so 

 great that it seemed most probable even as late as the hundredth 

 trial that these animals would never finish the learning process. 

 But from the hundredth trial on the animals were more eager for 

 food. There are two possible explanations for this change: (1) 

 As the subjects grew older they were better able to stand long 

 periods of starvation; (2) the organism doubtless tended to adapt 

 itself to its conditions. 



Dr. Carlson says, "That the young and growing individual 

 experiences greater hunger than the adult or aged individual is 

 common knowledge." This being the case it is most likely that 

 the period of eagerness for food ends earlier in the young than in 

 the adult individual. When one examines the retraining of the 

 group of animals trained with forty-eight hours of hunger he 

 finds this most interesting fact, that this group retrained more 

 rapidly than the other groups. That it made better average time 



