20/12 



DESIGN FOR A BRAIN 



2 the probability is 3/4 (instead of 1/4). Some empirical tests 

 gave the results of Table 20/12/2. 



Table 20/12/2. 



The probability is higher, but it still falls as n is increased. 



A similar series of tests was made with the homeostat. Units 

 were allowed to interact with settings determined by the uni- 

 selectors, and the percentage of stable combinations found when 

 the number of units was two; the percentage was then found 

 for the same general conditions except that three units interacted ; 



ioo 



50 



2 3 



number of variables 

 Figure 20/12/1. 



and then four. The general conditions were then changed and 

 a new triple of percentages found. And this was repeated six 

 times altogether. As the general conditions sometimes encour- 

 aged, sometimes discouraged, stability, some of the triples were 

 all high, some all low ; but in every case the per cent stable fell 

 as the number of interacting units was increased. The results 

 are given in Figure 20/12/1. 



224 



