DESIGN FOR A BRAIN 



8/9 



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 



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



V 



Di Dp 



1 w- 



Time »- 



Figure 8/9/1 : Three units interacting. The downstrokes at S are 

 forced by the operator. If 2 responds with a downstroke, the 

 trainer drives 3 past its critical surface. 



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

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

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

 Homeostat was tested again: again it produced the forbidden 

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

 At S 3 , the Homeostat was tested again: it moved in the desired 

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

 S 5 the Homeostat continued to show the desired reaction. 



From S x onwards, T's behaviour is determinate at every instant; 

 so the system composed of 1, 2, 3, T, and the uniselectors, is 

 state-determined. 



Another property of the whole system should be noticed. 

 When the movement-combination ' 1 and 2 moving similarly ' 

 occurs, T is thereby impelled, under the rules of the experiment, 

 to force 3 outside the region bounded by the critical states. Of 



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