258 The Animal Mind 



we repeat it over and over, relying on the certainty that 

 each repetition will make the next one easier. With this 

 law in mind as an essential postulate, we shall survey the 

 types of true learning found in the lower animals under the 

 following four heads : (i) learning involving the dropping 

 out of movements; (2) learning involving the formation 

 of series of movements ; (3) the recognition of landmarks ; 

 (4) learning involving the anticipation of movements. 



74. Learning Involving the Dropping Out of Movements 



Among all the movements which an animal is capable of 

 making, there are some which are closely connected with 

 the great needs of its existence, and others whose connec- 

 tion with such needs is only indirect and casual. The gen- 

 eral process of adjustment to environment which has made 

 the animal what he is, has so ordered matters that the 

 vitally important movements are in a state of especial 

 readiness to be performed. The nervous resistances along 

 the pathways leading to the muscles used in these move- 

 ments are congenitally low. Such responses are what 

 Sherrington (68 i, p. 229) has called "prepotent reflexes." 



Now if we survey all the cases in which an animal learns 

 by experience, we are obliged to conclude that on some 

 principle of economy of energy, isolated movements which 

 do not bring any consequences of importance to the organism 

 tend to be dropped, and their places taken by a state of rest. 

 This seems to be the law according to which we ourselves 

 cease to pay any attention to our familiar surroundings. 

 We cease to notice the ticking of a clock, although no adap- 

 tation takes place in the ear itself ; we sleep undisturbed 

 by the noise of the trolley cars which is distracting to 

 our friends from the country. The spider experimented 



