Is the Brain a Calculating Machine? 147 



It is this feature which gives continuity to our lives and to that of 

 all animals with a developed brain. We must therefore picture the 

 brain, not merely as a kind of telephone exchange for linking senses 

 with muscles, but as something which stores up to some extent every- 

 thing which has been experienced and unites it with the present. It 

 is essentially an organ of continuity and the very least that we can 

 say about its mechanism is that it must provide a means by which the 

 present can take its place within the record of the past. A calculating 

 machine which resembled a brain would thus have to be permanentiy 

 modified by every operation it performed. When presented with a 

 sequence of numbers, it would have to recognize in them features like 

 previous sequences, and perform operations which had produced suc- 

 cessful results before. It would be rather boring to press this any 

 further; but I think it will be evident that the gap between the brain 

 and the machine is very great. Indeed the real work of the machine is 

 still being done by the operators who set it up. 



We must however enquire a little further about what goes on in 

 real brains. We have found that patterns of stimulation arrive from 

 the senses in the receptor areas, and from these patterns of excitation 

 spread out through innumerable circuits to other regions. In these 

 regions they meet and are compared with patterns arising from pre- 

 vious experiences. How this is done we hardly know, as we do not 

 know how the memory record is stored, and how it is made available 

 for comparison. But it is evident that the original sensations are dealt 

 with at more than one level and finally we come to the level of aware- 

 ness and consciousness, at which the interpretation which has been 

 made is finally judged and action is set in motion or, possibly, no 

 action is decided upon. 



What is this level of consciousness? It seems as if there is something 

 in the brain which is capable of 'looking at' the images as they are 

 . formed at lower levels, which may either come from the actual sen- 

 sory impressions or from the memory record. We might, as an 

 analogy, think of the lower levels as like a television set which re- 

 ceives impulses and produces a picture from them. To produce a pic- 

 ture is, however, not to be conscious of it; and here we come to per- 

 haps the greatest mystery and the most difficult feature in the whole 

 range of living phenomena. 



For a scientist, consciousness and awareness are subjective 

 phenomena which are not capable of instrumental verification. We 

 are aware of what we experience ourselves, e.g. the sensation of green 

 when looking at a green field. We have absolutely no way of telling 

 what sensations other people are aware of, except from what they 

 tell us about their experiences. The sensation of green, which I am 



