THE DOMAIN OF INFORMATION THEORY 



IN BIOLOGY* 



Henry Quastler 



Brookhaven National Laboratory, Upton, New York 



In the proper course of events, a theory is introduced to account for a specific 

 body of facts ; then nobody will presume to expatiate upon the domain of the 

 theory. With information theory and biology, the situation is less simple. The 

 modern development of the theory stems largely from C. E. Shannon's concern 

 with certain problems of communication engineering (1). I have heard Shannon 

 say that he was somewhat dubious about the extension of his results to remote 

 fields, and that he felt that people working in other disciplines might do 

 better to develop their own theories. This is not what happened. Shannon's 

 theory has been taken up with enthusiasm by psychologists, linguists, historians, 

 planners, librarians, sociologists, and by biologists with a wide variety of 

 interests. Motives for such generalizations were supplied by Wiener, who 

 pointed out that all control (in the animal and in the machine) depended on 

 communication, and that all communication involved measurable quantities of 

 information (2) ; and by Weaver, who emphasized the great generality of the 

 information concepts in a searching study (1). 



It appeared then that information theory was a tool made to order to deal 

 with a vast variety of problems. This variety, however, is not limitless. There- 

 fore, a discourse on the domain of information theory is indicated. One part 

 of this discourse will deal with the negative domain, or with some of the limita- 

 tions of the theory. The other part will be concerned with positive applications ; 

 it is largely an attempt to give clearer definition to the somewhat vague hopes 

 most people have when proposing to apply information theory. 



It is curious that applied information theory produces rather violent reactions, 

 some of them negative. Certainly, it is entirely possible that every biologist 

 who works with information theory, or any other systems theory, is wasting 

 his time. But this, of course, applies to anybody who works with a new theory. 

 It is difficult to see how applying information theory should irritate people — 

 unless the cause should be the very pleasure of gently playing with the theory. 

 Every scientist is aware that there is a 'difference between the labor of thought, 

 and the sport of musing', and knows well the danger inherent in the latter. 

 To go on with Dr Johnson: 'There is nothing more fatal to a man whose 

 business is to think, than to have learned the art of regaling his mind with those 

 airy gratifications .... This is a formidable and obstinate disease of the intellect, 

 of which, when it has once become radicated in time, the remedy is one of the 

 hardest tasks of reason and of virtue. Its slightest attacks, therefore, should be 



* Research carried out at Brookhaven National Laboratory under the auspices of the U.S. 

 Atomic Energy Commission. 



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