DESIGN FOR A BRAIN 



11/10 



limits for success to be achieved; failure in either respect means 

 failure totally. 



The example par excellence occurs when the burglar, homeo- 

 statically trying to earn his daily bread by stealing, faces that 

 particular environment known as the combination lock. This 

 environment has, of course, been selected to be as difficult for 

 him as possible; and its peculiar difficulty lies precisely in the fact 

 that' partial successes — getting, say, six letters right out of seven 

 — count for nothing. Thus there can be no progression towards 

 the solution. Thus, confronted with an environment that does 

 not permit use to be made of partial adaptation, human and 

 Homeostat fail alike. 



Cumulative adaptation 



11/10. In terrestrial environments, however, such problems are 

 not common. Usually the organism has many essential variables, 

 and also it manages to reach an adaptation of all fairly quickly. 

 Let us take these apparently contradictory facts as data, and see 

 what can be deduced from them (following essentially the method 

 of S. 4/12). 



Quite a simple example will suffice to show the point. Let us 

 suppose that an organism has three essential variables (marked 

 1, 2 and 3) all affected by the environment, and all able to veto 

 the stability of the step-mechanisms S, as in Figure 11/10/1. 



Let us suppose that the organism has reached the state of being 



Figure 11/10/1. 

 154 



