1 76 Information Storage and Neural Control 



the world of communication, a message does not have to be an 

 event or an object in order to be a message. As my friend Ray 

 Birdwhistell says, "Nothing never iiappens." 



If we look at an on-going interchange between persons who 

 behave alternatively, they can never "not behave." The inter- 

 change has been going: . . . A, B, A, B, A, B, . . . From this 

 we cut out, for our analysis, any triad: a sequence A, B, A, or, 

 if you like, a sequence B, A, B. Within any such triad, we can now 

 recognize that the third item is necessarily a reinforcement be- 

 cause, in this triad, if the third item had been something other 

 than what it was, or if it had been something, for example, which 

 made the second item inappropriate, it would obviously have 

 been a negative reinforcement. So if the third item is appropriate, 

 it is, in fact, a positive reinforcement of the second item. By the 

 same token, the second item can always be regarded as a "response" 

 since it follows a first item and is reinforced by a third. Cor- 

 respondingly, the first item is necessarily a stimulus since it precedes 

 the second, which is reinforced by the third. These are purely 

 formal relations between items and must necessarily obtain in any 

 triad of an interchange between learning entities. 



It follows that, in a long interchange of this kind, any behavior 

 of B is necessarily simultaneously a stimulus, a response, and a 

 reinforcement, according to how we slide our identification of the 

 triad up and down the series. The same is true for any behavior 

 of A. Such a scheme has the advantage of presenting to the scien- 

 tist all the possibilities for punctuating a sequence of interchange 

 at the level of complexity of the triad. It is, however, arbitrary in 

 that it excludes the simpler (dyadic) units of interchange and also 

 the more complex (polyadic) units. 



The arbitrary selection of the trigram, however, does raise a 

 number of interesting problems. Note that each item in any tri- 

 gram is also a member of two other trigrams. Clonsider such a 

 sequence as the following: 



A . . . 23 25 27 29 . . . 



B ... 22 24 26 28 30 . . . 



In the sequence, the odd numbers represent items of A's behavior 

 while the even numbers represent those of B. The sequence is 



