DESIGN FOR A BRAIN 7/4 



7/4. Continuing to examine the case that gives the kitten the 

 maximal difficulty, let us consider the case in which the effects that 

 the various states of the environment will have on the essential 

 variables, though definite, is not known to the reacting part R. 

 This is the case of a bird, driven to a strange island and seeing a 

 strange berry, who does not know whether it is poisonous or not. 

 It is the case of the cat in Thorndike's cage, who does not know 

 whether the lever must be pushed to right or left for the door to 

 open. It is the assumption made in S.l/17, where the kitten was 

 confronted with a fire as an example of an organism in a situation 

 where its previous experience gave no reliable indication of how 

 the various states of the environment were paired to the states 

 1 within ' and c without ' the physiological limits of the essential 

 variables. 



To be adapted, the organism, guided by information from the 

 environment, must control its essential variables, forcing them to 

 go within the proper limits, by so manipulating the environment 

 (through its motor control of it) that the environment then acts 

 on them appropriately. Thus the diagram of immediate effects 

 of this process is 



Environment 



Essential 

 variables 



In the case we are considering, the reacting part R is not specially 

 related or adjusted to what is in the environment and how it is 

 joined to the essential variables. Thus the reacting part R can 

 be thought of as an organism trying to control the output of a 

 Black Box (the environment), the contents of which is unknown 

 to it. 



It is axiomatic (for any Black Box when the range of its inputs 

 is given) that the only way in which the nature of its contents 

 can be elicited is by the transmission of actions through it. This 

 means that input-values must be given, output-values observed, 

 and the relationships in the paired values noticed. In the kitten's 

 case, this means that the kitten must do various things to the 

 environment and must later act in accordance with how these 

 actions affected the essential variables. In other words, it must 

 proceed by trial and error. 



Adaptation by trial and error is sometimes treated in psycho- 



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