FULLY CONNECTED SYSTEMS 11/8 



Our present difficulties are, in fact, largely due to this assumption. 

 By modifying it we shall not only lessen the difficulties but we 

 shall obtain a model more like the real brain. 



The views held about the amount of internal connection in the 

 nervous system — its degree of ' wholeness ' — have tended to 

 range from one extreme to the other. The ' reflexologists ' from 

 Bell onwards recognised that in some of its activities the nervous 

 system could be treated as a collection of independent parts. They 

 pointed to the fact, for instance, that the pupillary reflex to light 

 and the patellar reflex occur in their usual forms whether the 

 other reflex is being elicited or not. The coughing reflex follows 

 the same pattern whether the subject is standing or sitting. And 

 the acquirement of a new conditioned reflex might leave a pre- 

 viously established reflex largely unaffected. On the other hand, 

 the Gestalt school recognised that many activities of the nervous 

 system were characterised by wholeness, so that what happened 

 at one point was related to what was happening at other points. 

 The two sets of facts were sometimes treated as irreconcilable. 



Yet Sherrington in 1906 had shown by the spinal reflexes 

 that the nervous system was neither divided into permanently 

 separated parts nor so wholly joined that every event always 

 influenced every other. Rather, it showed a richer, and a more 

 intricate picture — one in which interactions and independencies 

 fluctuated. ' Thus, a weak reflex may be excited from the tail 

 of the spinal dog without interference with the stepping-reflex '. 

 ... ' Two reflexes may be neutral to each other when both are 

 weak, but may interfere when either or both are strong '. . . . 

 4 But to show that reflexes may be neutral to each other in a 

 spinal dog is not evidence that they will be neutral in the animal 

 with its whole nervous system intact and unmutilated.' The 

 separation into many parts and the union into a single whole are 

 simply the two extremes on the scale of ' degree of connected- 

 ness '. 



Being chiefly concerned with the origin of adaptation and co- 

 ordination, I have tended so far to stress the connectedness of 

 the nervous system. Yet it must not be overlooked that adapta- 

 tion demands independence as well as interaction. The learner- 

 driver of a motor-car, for instance, who can only just keep the 

 car in the centre of the road, may find that any attempt at 

 changing gear results in the car, apparently, trying to mount 



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