158 



K. S. LASHLEY 



The drug seemed to affect all the animals that received it 

 in the same way. Of the 21 animals trained after injection 

 of caffeine only one required as few trials for learning as did 

 his individual control. The results of the comparison of indi- 

 vidual records are given in table 8. Further, no animal that 

 was given caffeine learned in fewer trials than the average of 

 the control animals, as appears from figure 3. 



Trials 



FIG. 3. A comparison of the number of trials required for learning by animals 

 trained after injection of caffeine with that required by normal ones. Arranged 

 as figure 1. 



The distance traversed in excess of the true pathway, or 

 approximately, the number of errors made, also shows the caffein- 

 ized animals inferior to the controls. The individual records 

 of excess distance are given in figure 4 and the averages in table 

 7. The proportions are somewhat less than those given by 

 the data on the number of trials but are still too large to be 

 explicable as the result of chance. 



