USE OF THE HANDS IN THE RHESUS MONKEY 



183 



trials he could no longer be induced to make any attempt to get 

 the food and further training had to be abandoned. 



Trials 



400 



Figure 1. — -The course of modification of the use of the right hand by training in 

 the case of monkey No. 1. The ordinates represent the number of times 

 that the right hand was used in each successive ten trials, the abscissae, the 



number of trials grouped by tens. ■ — first period of training. 



second period. 



No. 1 learned to inhibit the use of his right hand very quickly. 

 After nine successive failures to get the food with his right hand 

 he began to use his left predominantly and only 34 failures to 

 get the food were required to abolish completely the use of the 

 right hand in this one situation. The form of the learning curve 

 is shown in fig. 1. After the first hundred trials the left hand 

 was used in all but 2% of his efforts to get the food. 



When the habit seemed firmly established (after 500 trials) 

 the preferential use of the hands in the remaining six situations 

 was tested again. The data obtained are given in table 3. 

 In the three situations outside of the cage the training resulted 

 in a decrease in the use of the right hand. This is not very 

 certain where the animal took food from the experimenter's 

 left hand, since there was little room for improvement to begin 

 with, but it is unmistakable where food was picked up from the 

 floor. In contrast to this the training seems to have had little 

 effect in modifying the use of the hands when the animal was 

 in the cage, except in the last case, that of taking food from 

 the table. The change here from 59.0 to 4.4% in the use of 

 the right hand is significant. 



