INTERFERENCE AND LEARNING IN PALAEOCORTICAL 



SYSTEMS^ 



J. Olds and M. E. Olds 



Recent stimulation and single-unit studies in our laboratory have con- 

 vinced us that the hypothalamus with its projections to palaeocortical and 

 related structures bears some very special relation to mechanisms of 

 instrumental learning, and possibly to associative mechanisms in general. 



introduction 



In one sense all animal-learning experiments involve response learning, 

 for it is a changed response that signifies to the experimenter that some 

 learning has occurred. Nevertheless, it is possible to distinguish between a 

 type of learning that is mainly response learning, and another type that is 

 mainly a learning of associations. The former is evidenced when an animal 

 learns how to get food in a problem box; he has learned a new response, 

 he has learned what to do. The latter is evidenced when an animal learns 

 to salivate when a bell announces the present arrival of food; he does not 

 salivate to get food but because the bell is associated with food, and the 

 animal salivates as though the bell meant food. 



In the study of learning, two basic procedures have been used with 

 respect to these two types of learning. 



In instrumental conditioning, response learning is the salient feature of 

 the procedure. The experimenter has only one stimulus at his disposal (a 

 reward or punishment). He awaits the response which interests him, and, 

 when it occurs, proceeds to stimulate or to withdraw stimulation. If he 

 stimulates with what is called a 'reward', the response in question has its 

 repetition frequency augmented, and if the animal is rewarded again and 

 again, the response may quickly come to dominate the animal's repertory. 



In Pavlovian conditioning, association receives the emphasis. The 

 experimenter imposes first an 'irrelevant' stimulus and then a 'relevant 

 one. Eventually, the irrelevant response makes the animal 'think' of the 

 relevant one, or at least perform some response that we take as oblique 

 evidence of such a thought. Pavlovian conditioning is thus conceptualized, 



1 The research reported here was supported by grants from the Foundations Fund for 

 Research in Psychiatry, the National Institute of Mental Health, and the Ford Foundation, 



