1/5 DESIGN FOR A BRAIN 



Chapter 5, but in the simpler cases the improvement is obvious 

 enough. ' The burned child dreads the fire ' : after the experi- 

 ence the child's behaviour towards the fire is not only changed, 

 but is changed to a behaviour which gives a lessened chance of 

 its being burned again. We would at once recognise as abnormal 

 any child who used its newly acquired knowledge so as to get 

 to the flames more quickly. 



To demonstrate that learning usually changes behaviour from a 

 less to a more beneficial, i.e. survival-promoting, form would 

 need a discussion far exceeding the space available. But in this 

 introduction no exhaustive survey is needed. I require only 

 sufficient illustration to make the meaning clear. For this pur- 

 pose the previous examples will be examined seriatim. 



When a conditioned reflex is established by the giving of food 

 or acid, the amount of salivation changes from less to more. And 

 the change benefits the animal either by providing normal lubri- 

 cation for chewing or by providing water to dilute and flush away 

 the irritant. When a rat in a maze has changed its behaviour so 

 that it goes directly to the food at the other end, the new behaviour 

 is better than the old because it leads more quickly to the animal's 

 hunger being satisfied. The kitten's behaviour in the presence of 

 a fire changes from being such as may cause injury by burning to 

 an accurately adjusted placing of the body so that the cat's body 

 is warmed by the fire neither too much nor too little. The circus 

 animals' behaviour changes from some random form to one deter- 

 mined by the trainer, who applied punishments and rewards. 

 The animals' later behaviour is such as has decreased the punish- 

 ments or increased the rewards. In Man, the proposition that 

 behaviour usually changes for the better with learning would 

 need extensive discussion. But in the example of the finger 

 movements and the compound microscope, the later movements, 

 which bring the desired object directly to the centre of the field, 

 are clearly better than the earlier movements, which were dis- 

 orderly and ineffective. 



Our problem may now be stated in preliminary form : what 

 cerebral changes occur during the learning process, and why does 

 the behaviour usually change for the better ? What type of 

 mechanistic process could show the same property ? 



But before the solution is attempted we must first glance at the 

 peculiar difficulties which will be encountered. 



4 



