308 Information Storage and Neural Control 



upon the input, stores part of it, filters it, and transmits it over a 

 limited-capacity channel to long-term storage, to the output trans- 

 ducer, or to both. Here Broadbent includes all the components of 

 the individual system in one channel, which is one possible way 

 to view the system. This results, however, in ascribing to channel 

 activity some things which we have analyzed as subsystem functions. 

 Within the channel he analyzes components which filter, store, 

 decide, and so forth. 



Quastler (7) analyzes the activity of specific channels in terms 

 of speed, diversity, order of complexity, range, and other factors. 

 Electronics engineers measure in channels the variables of process- 

 ing time, channel capacity, bandwidth, signal-to-noise ratio, and 

 phase shift or lag. These can all be usefully applied to the animal 

 or human being. 



The processing time through neurons is brief compared to the 

 total response time. The duration of neural propagation of an 

 impulse differs with the length of the channel and the type and 

 size of the neuron. Longer transmission delays occur at the per- 

 ceiver and the decider. 



Channel capacity is a valuable concept in behavior theory. 

 Broadbent (8) says: "... perhaps the point of permanent value 

 which will remain in psychology if the fashion for communication 

 theory wanes, will be the emphasis on problems of capacity. The 

 latter, in communication theory, is a term representing the limiting 

 quantity of information which can be transmitted through a given 

 channel in a given time . . . the fact that any given channel has 

 a limit is a matter of central importance to communication engi- 

 neers, and it is correspondingly forced on the attention of psy- 

 chologists who use their terms." 



Quastler (9) was interested in finding how much information 

 man can process at best. His research, therefore, was designed so 

 that neither the visual input nor the muscular output were in 

 any way hampered. In these tasks all inputs came from a single 

 source, all output choices were mechanical, and all displays and 

 operations were thoroughly familiar. He studied rates at which 

 information is transmitted by reading, typing, playing the piano, 

 doing mental arithmetic, or assimilating by glancing at displays 



