Archive image from page 190 of Design for a brain (1954). Design for a brain . designforbrain00ashb Year: 1954 THE MULTISTABLE SYSTEM 16/5 The process can be illustrated on the homeostat. Tliree units were connected so that the diagram of immediate effects was 2 ± 1 ±: 3 (corresponding to A, B, and C respectively). To separate the effects of 2 and 3 on 1, bars were placed across the potentiometer dishes (Figure 8/8/2) of 2 and 3 so that they could move only in the direction recorded as downwards in Figure 16/5/1, while 1 could move either upwards or downwards. If 1 was above the central line
Archive image from page 190 of Design for a brain (1954). Design for a brain . designforbrain00ashb Year: 1954 THE MULTISTABLE SYSTEM 16/5 The process can be illustrated on the homeostat. Tliree units were connected so that the diagram of immediate effects was 2 ± 1 ±: 3 (corresponding to A, B, and C respectively). To separate the effects of 2 and 3 on 1, bars were placed across the potentiometer dishes (Figure 8/8/2) of 2 and 3 so that they could move only in the direction recorded as downwards in Figure 16/5/1, while 1 could move either upwards or downwards. If 1 was above the central line (shown broken), 1 and 2 inter- acted, and 3 was independent; but if 1 was below the central line, then 1 and 3 interacted, and 2 was independent. 1 was u jVlm n —\j—\r v Time Figure 16/5/1 : Three units of the homeostat interacting. Bars in the central positions prevent 2 and 3 from moving in the direction corre- sponding here to upwards. Vertical strokes on U record changes of uniselector position in unit 1. set to act on 2 negatively and on 3 positively, while the effects 2 —>- 1 and 3 —> 1 were uniselector-controlled. When switched on, at J, 1 and 2 formed an unstable system and the critical state was transgressed. The next uniselector connections (K) made 1 and 2 stable, but 1 and 3 were unstable. This led to the next position (L) where 1 and 3 were stable but 1 and 2 became again unstable. The next position (M) did not remedy this ; but the following position (N) happened to provide connections which made both systems stable. The values of the step-functions are now permanent; 1 can interact repeatedly with both 2 and 3 without loss of stability. It has already been noticed that if A, B and C should form from time to time a triple combination, then the step-functions 175
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