THE PROBLEM 1/5 



reflex can be made at will to react to the sound of a bell either 

 with or without salivation. Further, once trained to react in 

 one way it may, with little difficulty, be trained to react later in 

 the opposite way. The salivary response to the sound of a bell 

 cannot, therefore, be due to a mechanism of fixed properties. 



A rat selected at random for an experiment in maze-running 

 can be taught to run either to right or left by the use of an appro- 

 priately shaped maze. Further, once trained to turn to one side 

 it can be trained later to turn to the other. 



A kitten approaching a fire for the first time is unpredictable 

 in its first reactions. The kitten may walk almost into it, or 

 may spit at it, or may dab at it with a paw, or may try to sniff 

 at it, or may crouch and ' stalk ' it. The initial way of behaving 

 is not, therefore, determined by the animal's species. 



Perhaps the most striking evidence that animals, after training, 

 can produce behaviour which cannot possibly have been inborn 

 is provided by the circus. A seal balances a ball on its nose for 

 minutes at a time ; one bear rides a bicycle, and another walks 

 on roller skates. It would be ridiculous to suppose that these 

 reactions are due to mechanisms both inborn and specially per- 

 fected for these tricks. 



Man himself provides, of course, the most abundant variety of 

 learned reactions : but only one example will be given here. If 

 one is looking down a compound microscope and finds that the 

 object is not central but to the right, one brings the object to 

 the centre by pushing the slide still farther to the right. The 

 relation between muscular action and consequent visual change 

 is the reverse of the usual. The student's initial bewilderment 

 and clumsiness demonstrate that there is no neural mechanism 

 inborn and ready for the reversed relation. But after a few days 

 co-ordination develops. 



These examples, and all the facts of which they are representa- 

 tive, show that the nervous system is able to develop ways of 

 behaving which are not inborn and are not specified in detail 

 by the gene-pattern. 



1/5. Learned behaviour has many characteristics, but we shall 

 be concerned chiefly with one : when animals and children learn, 

 not only does their behaviour change, but it changes usually for 

 the better. The full meaning of i better ' will be discussed in 



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