Chapter 6 



THE BLACK BOX 



6/1. The methods developed in the previous chapters now enable 

 us to undertake a study of the Problem of the Black Box; and the 

 study will provide an excellent example of the use of the methods. 



The Problem of the Black Box arose in electrical engineering. 

 The engineer is given a sealed box that has terminals for input, to 

 which he may bring any voltages, shocks, or other disturbances he 

 pleases, and terminals for output, from which he may observe what 

 he can. He is to deduce what he can of its contents. 



Sometimes the problem arose literally, when a secret and sealed 

 bomb-sight became defective and a decision had to be made, without 

 opening the box, whether it was worth returning for repair or whether 

 it should be scrapped. Sometimes the problem arose practically, as 

 when a telephone engineer considered a complicated set of relations 

 between tests applied and results observed, in the middle of a mass 

 of functioning machinery that was not to be dismantled for insuffi- 

 cient reason. 



Though the problem arose in purely electrical form, its range of 

 apphcation is far wider. The chnician studying a patient with brain 

 damage and aphasia may be trying, by means of tests given and 

 speech observed, to deduce something of the mechanisms that are 

 involved. And the psychologist who is studying a rat in a maze 

 may act on the rat with various stimuli and may observe the rat's 

 various behaviours; and by putting t-he facts together he may try to 

 deduce something about the neuronic mechanism that he cannot 

 observe. I need not give further examples as they are to be found 

 everywhere (S.6/17). 



Black Box theory is, however, even wider in application than these 

 professional studies. The child who tries to open a door has to 

 manipulate the handle (the input) so as to produce the desired 

 movement at the latch (the output); and he has to learn how to 

 control the one by the other without being able to see the internal 

 mechanism that links them. In our daily lives we are confronted 

 at every turn with systems whose internal mechanisms are not fully 

 open to inspection, and which must be treated by the methods 

 appropriate to the Black Box. 



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