9/5 DESIGN FOR A BRAIN 



by a device as simple as a sheet of glass (in the example of the 

 pike) ; and because the rules of the training are to be decided in 

 advance (as when we decide to punish a house-dog whenever he 

 jumps into a chair), and therefore to be invariant throughout 

 the process. Suppose then that jumping into a chair always 

 results in the dog's sensory receptors being excessively stimulated. 

 As an ultrastable system, step-function values which lead to 

 jumps into chairs will be followed by stimulations likely to cause 

 them to change value. But on the occurrence of a set of step- 

 function values leading to a remaining on the ground, excessive 

 stimulation will not occur, and the values will remain. (The 

 cessation of punishment when the right action occurs is no less 

 important in training than its administration after the wrong 

 action.) 



The process can be shown on the homeostat. Figure 9/5/1 

 provides an example. Three units were joined : 



and to this system was joined a ' trainer ', actually myself, which 

 acted on the rule that if the homeostat did not respond to a 

 forced movement of 1 by an opposite movement of 2, then the 

 trainer would force 3 over to an extreme position. The diagram 

 of immediate effects is therefore really 



>T 



Part of the system's feedbacks, it will be noticed, pass through T. 

 At S v 1 was moved and 2 moved similarly. This is the * for- 

 bidden ' response ; so at D 1} 3 was forced by the trainer to an 

 extreme position. Step-functions changed value. At S 2 , the 

 homeostat was tested again : again it produced the forbidden 

 response ; so at Z) 2 , 3 was again forced to an extreme position. 

 At £3, the homeostat was tested again : it moved in the desired 

 way, so no further deviation was forced on 3. And at *S 4 and 

 $5 the homeostat continued to show the desired reaction. 



116 



