DESIGN FOR A BRAIN 15/11 



connexions that transmit disturbances down the chain. If their 

 capacity is high, so much disturbance may be transmitted to the 

 lower members of the chain that their adaptations may be post- 

 poned indefinitely. If their capacity is low, the attenuation may 

 be so rapid that C, though affected by B, may be practically 

 unaffected by what happens at A; and a further subsystem D 

 may be practically unaffected by those at B; and so on. Thus, 

 as the connexions between the subsystems get weaker, so does 

 adaptation tend to the sequential — first A, then B, then C, and 

 so on. (The limit, of course, is the iterated set.) 



If the adaptation is sequential, the behaviour corresponds to 

 that of Case 2 (S. 11/5). The time of adaptation will then be 

 that of the moderate T 2 rather than that of the excessively long 

 2\. Thus adaptation, even with a large organism facing a large 

 environment, may be achievable in a moderate time if the environ- 

 ment consists of subsystems in a chain, with only channels of 

 small capacity between them. 



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