<,6o 



BRAIN MECHANISMS AND LEARNING 



procedure they arc not. Here the difference between the two procedures 

 is that in the 'effortless' condition the manipulanda are easy to move, 

 whereas in the 'effortful' condition they can be moved only with great 

 difficulty. Since visual cues are excluded the sensory information necessary 

 for making the discrimination in either condition cannot be obtained until 

 the response is actually initiated. But once the response has been initiated 

 the monkey has a strong tendency to complete it, regardless of the dis- 

 criminanda. In the 'effortless' condition, where it is possible to complete 



AUDITORY DISCRIMINATION LEARNING and PERFORMANCE 



100- 



50- 



NO SHOCK 



SHOCK 



SHOCK REMOVED 



SHOCK RETURNED 



(ROSVOLD, BATTIG, MISHKIN -UNPUBLISHED ) 



Fig. 5 



Effects of frontal lesions on auditory discrimination learning and performance 

 with two different training procedures. 



the response with case, the frontal annuals seem to learn the discrimination 

 relatively slowly. In the 'effortful' condition, on the other hand, where 

 completing the response requires considerable strength, frontal animals 

 learn the relevant tactual discrimination as quickly as the controls.^ Thus, 

 unless frontal monkeys are effectively deterred from completing a response 

 which they have already initiated, they will do so regardless of the dis- 

 criminanda, and appear to have a tactual deficit when in fact they do not. 

 A particularly dramatic example of the effect of a non-sensory variable 

 is shown in Fig. 5. As with the visual and tactual discriminations, it may 



^ The two graphs in this figure represent the performance of animals from different studies. 

 Therefore, the absolute levels of performance in one study cannot be compared with those in 

 the other. The appropriate comparison is each frontal group with its own control. 



