Reading Rates and the Information Rate of 



a Human Channel 



By J. R. PIERCE and J. E. KARLIN 



(Manuscript received August 31, 1956) 



The limitatioyi on the rate at which information can he transmitted over an 

 ordinary telephone channel is a human one. In this study people read words 

 as fast as they were able to; from these results some deductions are made about 

 the capacity of a human being as an information channel. The discrepancy 

 between human channel capacity measured thus {40-50 bits/ sec) and tele- 

 phone and television channel capacity (about 50,000 bits/ sec and 50,000,000 

 bits/ sec respectively) is provocative. 



Introduction 



In communication over an ordinary telephone channel, the Hmitation 

 on the rate at which information can be transmitted appears to be a 

 human one. For instance, by use of a vocoder, the required channel 

 capacity can be reduced greatly with only a moderate reduction in the 

 quality of the reproduced speech.^ 



It would be of great interest to measure the information rate necessary 

 to provide a satisfactory sensory input to a human being. It is not clear 

 how this could be done. Something which may be related and for which 

 a lower bound can be measured is the capacity of a human being as an 

 information channel. 



An evaluation of and understanding of the limitations on the informa- 

 tion rate of the human channel might ultimately be of practical im- 

 portance for two reasons. First, it might help to tell us what sort of task 

 to set a human being when he is necessarily a part of a system involving 

 information transmission. Thus, a man can transmit information faster 

 by reading than by tracking. Secondly, the understanding might some- 

 what illuminate the problem of the channel capacity necessary to provide 

 a satisfactory sensory input, and so might help to reduce the channel 

 capacity required in electrical communication between human beings. 



Previous investigations indicate^- ^ that reading aloud attains the 

 fastest rate at which a human being can be demonstrated to transmit 



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