70 ETHICAL ASPECTS OF EVOLUTION 



argument, we may pause to consider an ingenious applica 

 tion of the law of Hedonic selection , which is found in 

 Mr. McDougall s excellent manual of Physiological Psychology 

 (p. 146 sq.). He is in search of a principle which may explain 

 the observed fact that a series of movements which leads 

 to the achievement of a desired result is repeated, and 

 tends to be perpetuated as a habit, whereas other tentative 

 movements, by which the same result is not achieved, are 

 not repeated ; and he finds that principle in the association 

 of achievement with pleasure, which he believes stamps 

 in the successful process . 



It is obvious that the interest of the law lies, not in 

 its scientific, but in its teleological aspects. The first in 

 stance which is given as suggesting it is the following. 

 A cat is imprisoned in a cage with a door which opens and 

 shuts with a catch. Food is placed within sight, and hunger 

 excites the cat to random movements in the direction of 

 escape, until one of those movements, not less random than 

 the rest, has the effect of opening the catch. After a number 

 of repetitions, which are not always the same, the cat 

 performs the successful movement at once, whenever the 

 experiment is tried. 



We may ask, What exactly does this amount to ? In 

 the first place, there is no conflict of impulses. The cat is 

 not called on to decide between the attractions of the meat 

 on one side, and those of a suitor on the other, or its duty to 

 leave the meat to a litter of starving kittens. All that has 

 happened is that instead of being obliged to wait on chance, 

 it has acquired a habit which enables it to satisfy a single 

 impulse at once. That it should possess habits of this kind, 

 which place the satisfaction of its wants, generally, beyond 

 the dominion of pure chance, is obviously a matter of prime 

 importance in the adaptation of every animal in all stages 

 of evolution. The same habits would be needed even if, 

 by some perverse arrangement, pain instead of pleasure 

 were associated with the satisfaction of an impulse : and, 

 in order to secure their establishment, nature has endowed 

 cats as well as men, but in a lower degree, with memory. 



