134 Inside the Living Cell 



leaves possible a degree of freedom and spontaneity, because in the 

 last resort they are able to and, in fact, must make a choice between 

 the various possible actions which are open to them. 



It must be recognized that there is always an element of spon- 

 taneity in an animal's response to its sensations, sometimes more 

 prominent and sometimes less prominent. It occurs even in very 

 simple organisms and is very deeply rooted in Nature. It existed, in- 

 deed, before the development of brains and nerves. The amoeba 

 pushes out its pseudopodia in an apparently aimless way; its proto- 

 plasm moves first one way and then another without apparent rhyme 

 or reason. The Paramecium oscillates endlessly in the water in its 

 search for food. Such movements are perhaps a consequence or re- 

 flection of the Brownian movements of small particles as they are 

 buffeted about by the ceaseless and chaotic thermal motions of matter. 



It is a long way from this to even the most irregular movements of 

 animals, but it seems a reasonable inference that undirected move- 

 ments come first and are reduced to order. The animal does not so 

 much have to initiate movements as to impose order and control on 

 the aimless movements of its limbs. It has to co-ordinate many in- 

 coherent movements into purposeful and effective actions. 



Craik's suggestion provides a possible way in which this is 

 achieved. It is a method of finding solutions, by trial and error, of the 

 problems set by the senses. The brain acts as a kind of super- 

 computer in solving these problems. Those movements which it fore- 

 sess will probably be inadequate are rejected. The control narrows 

 down the range of actions to those which seem to satisfy the require- 

 ments of the situation. 



However, it is important to realize that an element of spontaneity 

 remains, and is necessary because, otherwise, there would be no 

 actions from which the most suitable could be selected. This spon- 

 taneity is perhaps a relic of the undirected movements of the young 

 animal, of its playfulness when it is learning to co-ordinate its muscles 

 with its sense impressions. A kitten uses its muscles in a frankly ex- 

 perimental way. The movements are at first spontaneous and un- 

 directed, and it learns only gradually to co-ordinate them so as to pro- 

 duce effective actions within its ^picture' of the surroundings. But 

 even in the adult animal, there remains an element of play or ad- 

 venture — call it what you will — which is necessary if the animal is 

 to continue to live successfully. It may be very dangerous to lose this 

 element of initiative, since an animal which can perform actions 

 which are perfectly adapted to a particular environment may be un- 

 able to cope with changed conditions. The animals which have sur- 

 vived the changes caused by human activities are those which were 



