15/2 ADAPTATION IN ITERATED AND SERIAL SYSTEMS 



It is clear that the ecological world of Paramecium contains 

 many part-functions, and so too do the worlds of most living 

 organisms. 



A total environment, or universe, that contains many part- 

 functions, will show dispersion, in that the set of variables active 

 at one moment will often be different from the set active at another. 

 The pattern of activity within the environment will therefore tend, 

 as in S. 13/18, to be fluctuating and conditional rather than 

 invariant. As an animal interacts with its environment, the 

 observer will see that the activity in the environment is limited 

 now to this set, now to that. If one set persists active for a long 

 time and the rest remains inactive and inconspicuous, the observer 

 may, if he pleases, call the first set ' the ' environment. And if 

 later the activity changes to another set he may, if he pleases, 

 call it a ' second ' environment. It is the presence of part- 

 functions and dispersion that makes this change of view reasonable. 



An organism that tries to adapt to an environment composed 

 largely of part-functions will find that the environment is composed 

 of subsystems which sometimes are independent but which from 

 time to time show linkage. The alternation is shown clearly 

 when one learns to drive a car. The beginner has to struggle 

 with several subsystems: he has to learn to control the steering- 

 wheel and the car's relation to road and pedestrian; he has to 

 learn to control the accelerator and its relation to engine-speed, 

 learning neither to, race the engine nor to stall it; and he has to 

 learn to change gear, neither burning the clutch nor stripping the 

 cogs. On an open, level, empty road he can ignore accelerator 

 and gear and can study steering as if the other two systems did 

 not exist ; and at the bench he can learn to change gear as if steer- 

 ing did not exist. But on an ordinary journey the relations vary. 

 For much of the time the three systems 



driver + steering wheel + . . . 

 driver + accelerator + . . . 

 driver -f- gear lever -J- • • • 



could be regarded as independent, each complete in itself. But 

 from time to time they interact. Not only may any two use 

 common variables in the driver (in arms, legs, brain) but some 

 linkage is provided by the machine and the world around. Thus, 

 any attempt to change gear must involve the position of the 

 accelerator and the speed of the engine; and turning sharply 



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