1 74 Information Storage and Neural Control 



ments generally ignore phenomena of this order. Their experiments 

 are concentrated upon a change in the way the receiving entity 

 responds to what is supposed to be the same bit when this bit is 

 presented on successive occasions. 



"Learning," as the word is used by psychologists, denotes the 

 receipt of a meta-bit, i.e., a piece of information which will change 

 the subject's response to some bit. Over and over the psychological 

 experimenter presents the stimulus, a buzzer, followed by meat 

 powder. He observes that, after a number of trials, the animal 

 which formerly did not salivate when it heard the buzzer now 

 does salivate. This change is called "learning." But when this 

 process has approached completion, if the psychologist again 

 presents the buzzer and the animal salivates, this receipt of infor- 

 mation — the receipt of the sound of the buzzer as a yes or no 

 answer to a question which the animal can now identify — is not 

 usually regarded as learning. By including this simplest phenom- 

 enon, i.e., the receipt of the single bit, within the spectrum of 

 learning, the question as to whether a computer is or is not learning 

 when it receives appropriate input is answered out of hand. This 

 is learning of the simplest order. 



Second order learning arises when the subject changes his ability 

 to receive the yes or no answer to a question. This is, in fact, the 

 phenomenon which psychologists have studied maximally in learn- 

 ing experiments; the dog learns that the buzzer means future 

 meat powder. 



But beyond this, there is obviously a third order of learning 

 called the acquisition of "test wisdom," or "set learning." Here 

 the subject learns that he is to be on the lookout for sequences 

 of a certain sort in his universe, which include both external 

 events and his own behaviors. For example, he learns to behave 

 instrumentally in order to solve the problems presented by stimuli. 

 If the laboratory is Pavlovian, he learns to expect the stimuli to 

 be direct predictions of future reinforcements which will come 

 regardless of his action. I shall speak of this as third order learning, 

 referring to those changes whereby the subject who encounters 

 and solves repeated problems of a certain sort comes to expect 

 his universe to be structured in ways related to the formal struc- 

 turing of these previous problems. 



