DESIGN FOR A BRAIN 7/6 



and it acts on the parameters S. The first feedback plays its 

 part within each reaction; the second determines which reaction 

 shall occur. 



7/6. Since the argument here is crucial, let us trace it in detail, 

 using the basic operational concepts of S. 2/7-10. 



We start with the common observation that the burned kitten 

 dreads the fire. Translated into full operational form, this 

 observation becomes: 



(1) with the essential variables within their limits, the overt 



behaviour (of R) is such as is consequent on the parameters 

 having values S^ 



(2) when the essential variables are sent outside the limits (i.e 



if the kitten is burned), the overt behaviour is such as is 

 consequent on their having values 5 2 . 



That the overt behaviour is changed shows that S 2 is not the same 

 as S v Thus the two different values at the essential variables 

 have led to different values at S; there is therefore an immediate 

 effect from the essential variables to the parameters S. 



111. The same data will now provide us with the necessary 

 information about what happens within the second loop, i.e. 

 how the essential variables affect the parameters. 



The basic rule for adaptation by trial and error is: — If the 

 trial is unsuccessful, change the way of behaving ; when and only 

 when it is successful, retain the way of behaving. Now consider 

 the system S and how it must behave. Within this system are 

 the variables that are identical with the parameters to R (a mere 

 change of name), and to this system the essential variables are 

 parameters, i.e. come as input. The basic rule is equivalent to 

 the following formulation: 



(1) When the essential variables are not all within their normal 



limits (i.e. when the trial has failed), no state of S is to 

 be equilibrial (for the rule here is that S must go to some 

 other state). 



(2) When the essential variables are all within normal limits 



then every state of *S is to be equilibrial (i.e. S is to be in 

 neutral equilibrium). 



84 



