296 Information Storage and Neural Control 



DISCUSSION OF CHAPTER XII 



Bernard Saltzberg (Santa Monica, California): In the head- 

 phone experiment, I assume you used a single noise source which 

 divided its power between the earphones. Was an experiment 

 attempted with two independent noise sources? How did the 

 results come out? 



Warren S. McCulloch (Cambridge, Massachusetts) : It does not 

 help much. It has to be the same noise. Different noise is no good. 

 What they were trying when I was last involved was lagging one 

 earphone a little behind the other to see what phase difference 

 they could make in it and still have it work. As far as I know, this 

 has not been cleaned up yet. 



Gregory Bateson (Palo Alto, California): What is the price 

 of this increased reliability in terms of loss of educability? Obviously, 

 to obtain a new function — a new relationship — out of this net, you 

 have to alter a large number of connections. In a sense, I suspect 

 that the more reliable your new constructions, the more non- 

 educable the net becomes; but I am not a good enough logician 

 to know that this is so. 



McCulloch: Look at the flexibility end of it. We have here a 

 neuron with a couple of inputs (A and B) and one output neuron. 

 Let us take the case of three neurons. Incidentally, I cannot build 

 this without the interaction of afferents. I have one output neuron. 

 Now I can send signals back from the central nervous system and 

 tell my eye what it is to look for, what it is to see. You get 256 

 possible logical functions. You can calculate 253 of them by giving 

 these first rank neurons a nudge on the threshold. Reliability 

 does not mean that the net is inflexible. This is a remarkably 

 flexible device. The flexibility goes up with the anastomosis; it 

 does not go down. That is one of the beautiful things about it. 

 If it was simple majority logic, the situation would be impossible. 

 The stupidest thing to do, so to speak, if you want to get the 

 maximum life out of a rope is to use it until it breaks and then 

 replace it with another one. No mountain climber that I know 

 takes such a chance. The next worse thing is always to stretch 

 two ropes from man to man. What you want is the richness of 



