PREFACE 



Since the proposal of the two-factor dynamical model of neural 

 activity by Professor Rashevsky in his book, Mathematical Biophysics, 

 a great deal of work has been done in the formal development of the 

 theory as well as in the applications to specific psychological problems. 

 It is only natural that these developments by various authors over a 

 period of time will be lacking somewhat in coherence and continuity. 



With this in view, it seems appropriate to pause at the present 

 time to review the work which has been done so far to explain sys- 

 tematically the techniques, to summarize and describe such structures 

 as have been devised and the applications made, to suggest promising 

 directions for future development, to indicate types of experimental 

 data needed for adequate checks, and also to present new material not 

 published elsewhere. It is the hope that this perspective of past 

 achievements and, still more, of future prospects, will be of benefit to 

 those theorists and experimenters alike who are interested in con- 

 tributing to the understanding of some of the mechanisms which un- 

 derlie psychological processes. 



While perhaps the names which most commonly run throughout 

 the monograph are those of the authors themselves, this is largely 

 only a reflection of their dominating interests in its preparation; and 

 neither the monograph itself nor the papers of the authors and of 

 many others herein referred to would ever have seen the light of day 

 had not the general procedures and fundamental postulates been pre- 

 viously developed by Professor Rashevsky. For this, and for other 

 reasons too abundant to enumerate, the authors owe to him their 

 foremost debt of gratitude. 



Their thanks are due also to Dr. Warren S. MeCulloch, Dr. Ger- 

 hardt von Bonin, and Dr. Ralph E. Williamson for many helpful sug- 

 gestions made during the preparation of the manuscript, and to Mr. 

 Clarence Pontius for preparing all the original drawings ; to Mrs. Gor- 

 don Ferguson and Miss Helen De Young for typing of the manuscript, 

 to Miss Gloria Robinson for final preparation of the manuscript, 

 proofreading, and preparation of the index. For help with the latter 

 thanks are also due to Mr. Richard Runge. 



The authors also wish to thank the Editor of The Bulletin of 

 Mathematical Biophysics for permission to reproduce Figures 1 and 

 2 of chapter vi ; Figure 2 of chapter vii ; Figures 3, 4, 9, and 10 of 

 chapter ix ; Figures 2, 3, and 4 of chapter xi, Figure 1 of chapter xiii 

 and Figure 1 of chapter xiv. To the Editors of Psychometrika, their 

 thanks are due for permission to reproduce Figures 1, 6, 7, and 8 of 

 chapter ix, and to The University of Chicago Press for permission to 



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