38 Information Storage and Neural Control 



We see in the works of McCulloch and Rochester a feature 

 which distinguishes them from many other efforts at describing 

 brain activity and behavior. This new approach may be con- 

 trasted with many behavior theories which describe the product 

 or output of the system rather than the process by which the 

 output is obtained. Akhough it is perfectly reasonable to develop 

 a science of psychology from product models, psychological 

 theories would be more directly useful to neurophysiology if they 

 could be stated as process models. The absence of analytic tech- 

 niques and languages for describing processes has until recently 

 blocked any rigorous development of psychological process models. 

 The development of computer sciences offers hope of removing 

 these blocks. 



In order to provide a clearer picture of what is meant by the 

 infoimation processing theory approach, I wish to contrast a 

 process model with three other types of theoretical descriptions. 

 All four of the models to be discussed deal with human language 

 production. The three non-process theories, in fact, purport to 

 explain exactly the same phenomenon; unfortunately, the infor- 

 mation processing model does not. However, I think the exposition 

 will not suffer excessively from this lack of aesthetics. 



The phenomenon described by the three non-process models 

 is the strikingly regular statistical distribution of words produced 

 in speech and writing. The data are most often displayed in what 

 is called the standard curve, which is obtained as follows. A 

 passage of text is examined to determine which word occurs with 

 greatest frequency, which with second greatest frequency, and so 

 on. A graph is then made, with this rank plotted on the abscissa 

 and frequency of occurrence on the ordinate. Thus, if "the" is 

 the most frequent word, and if it occurs one thousand times, then 

 the point so determined is (1, 1000). Such graphs, made from a 

 wide variety of sources, are well-approximated by the equation 



Jr =C, 

 where 



/ = frequency, 

 r = rank, and 

 C = Constant. 



