214 ANIMAL BEHAVIOUR 



ing modification. A crab or a crayfish learns in a week or 

 two to distinguish infallibly between the right way and the 

 wrong way to food and freedom. How far down this capac- 

 ity extends we do not know; perhaps it requires a nervous 

 system of considerable complexity. If we obey the law of 

 parsimony, we are led to the conclusion that the creature 

 under sufficient stimulus of reward and "of shortening a 

 period of unpleasantness and unrest ", forms a habit without 

 ' knowing how ', though probably with high-strung attention 

 and delicate quivering sensitiveness, and precise registration 

 of sequences of movements ; and that after the trick has been 

 learned it trusts itself, as a piano-player does who learns in 

 quite a different way. Miss Washburn notes that " an ani- 

 mal that has gone astray on the path will often find the way 

 back to the starting-point, and from there traverse the whole 

 road rapidly and unerringly, apparently in the same way 

 that a piano-player who has a piece " at his fingers' ends ", 

 but has stumbled in a passage, can go through with entire 

 success if he starts over again. As piano-players know, 

 in such a case it is much better not to attend to stimuli 

 at all, but to think of something else; the movements will 

 take care of themselves better if consciousness intervenes as 

 little as possible " (1909, p. 231). 



Many experiments have been made with rats, dogs, cats, 

 chicks, and other creatures, which learn in the course of 

 time to find their way out of labyrinths and puzzle-boxes. 

 After some practice they are left in peace for a few days 

 and then replaced in the previous situation. It is observed 

 that they make fewer useless movements, that they sometimes 

 make none. The question is whether ideas are at work, 

 whether the creatures think. Have they remembered images 

 of their successful movements, or do they obey the prompt- 



