REWARD AND PUNISHMENT IN HABIT FORMATION 267 



107. Number 105 would get out of the electric box fairly rap- 

 idly but 107 did not seem much disturbed by the shock and took 

 its time in getting off the electric plates. The experimenter is 

 convinced that the difference in time taken for 107 to perfect the 

 habit and the time taken for 1 10 to perfect the same habit is not 

 primarily a difference in the learning capacities of the two sub- 

 jects but a difference in favorableness of the conditions of learning. 

 With a stimulus of one hundred and fifty units probably number 

 107 would have even surpassed 110 in the learning process. 

 There is little doubt that a stronger stimulus would have been 

 more favorable to the learning of both 107 and 105. Both of 

 these subjects were slightly lighter than the other rats of this 

 group, but the runt of the entire series was trained with hunger 

 of twenty-four hours and surpassed any of the other animals 

 trained with this degree of hunger. The fairly weak stimuli 

 were more favorable to the observation of individual differences 

 than stronger stimuli, as the stronger stimuli called forth vigorous 

 reaction in the least sensitive subjects. 



How may we account for the increase in the number of trials 

 required for the habit formation as the strength of stimulus in- 

 creased from about seventy-five units up to one hundred and 

 fifty units? One hundred and fifty units is far below the point 

 of injury to the subject. The only thing to account for this dif- 

 ference that was observable to the experimenter was less nerv- 

 ousness on the part of subjects trained with seventy-five units 

 than subjects trained with the stronger stimuli. Subjects 

 trained with seventy-five units approached the electric box more 

 cautiously and sometimes put their noses into the dark box, then 

 withdrew and entered the light box, while subjects trained with 

 stronger shock would rush into one of the boxes seemingly trying 

 to escape from the situation by running over the grill. Thus 

 it seems that the primary cause for the differences in length of 

 time required for rats to perfect the habit of always choosing the 

 light box when trained with a rather weak stimulus and when 

 trained with stronger stimuli is due to the disturbing factor of 

 excitation. 



