EFFECTS OF STRYCHNINE UPON RATE OF LEARNING 



157 



5. Apparently the strychnine so given had a retarding effect 

 upon learning, but while the difference between the strychnin- 

 ized animals and their controls is fairly great, the number of 

 animals is so small that no dependence can be placed upon the 

 difference. In this case the dose was graduated to the weight 

 of the animals, 0.10 mgm. of strychnine to each hundred grams 

 weight of the animal so that the immediate effects of the drug 

 resembled those found in the first experiment. The test suggests 

 that the acceleration of learning found for groups A and E is 

 the result of the immediate action of the drug. 



The influence of caffeine on the rate of learning. The tests 

 of the effects of caffeine were made in the same way as those 

 with strychnine. Three groups of rats were trained after doses 



TABLE 5 



A comparison of the number of trials required for learning by rats after injection 

 of water before training, and of 0.10 mgm. of strychnine after 

 each day's practice 



of 0.50 mgm. and 1.00 mgm. of the drug and others receiving 

 only water were trained at the same time. The average num- 

 bers of trials required for learning, as estimated from the first 

 errorless run and from three successive errorless runs, are given 

 in table 6. In groups G and H the dose was regulated to the 

 weight of the different animals on the basis of the above doses 

 for an hundred gram rat, so that these groups received relatively 

 more of the drug than did group C. 



In every case the rats receiving caffeine required a greater 

 number of trials for learning than did their water controls. 

 The differences are quite large, from one and one half to three 

 times as many trials being required by the caffeinized animals 

 as by normal ones. The differences between the groups are 

 at least three times their probable errors and hence significant. 



