74 BIOLOGICAL LECTURES. 



definite way. Popularly speaking, it has learned to open a door 

 by turning a button. To the uninitiated observer the behavior 

 of the six kittens that thus freed themselves from such a box 

 would seem wonderful and quite unlike their ordinary accom- 

 plishments of finding their way to their food, beds, etc., but the 

 reader will realize that the activity is of just the same sort as 

 that displayed by the chick in the pen. A certain situation 

 arouses, by virtue of accident or, more often, instinctive equip- 

 ment, certain impulses and corresponding acts. One of these 

 happens to be an act appropriate to secure freedom. It is 

 stamped in in connection with that situation. Here the act 

 is " clawing at a certain spot" instead of "running to E" and 

 is selected from a far greater number of useless acts. 



In the examples so far given there is a certain congruity 

 between the impulse associated with the situation and the result. 

 The act which lets the cat out is hit upon by the cat while try- 

 ing to get out, and is, so to speak, a likely means of release. But 

 there need be no such congruity between act and result. If we 

 confine a cat and open the door and let it out to get food only 

 when it scratches itself, we shall, after enough trials, find the 

 cat scratching itself the moment it is put into the box. Yet 

 in the first trials it did not scratch itself in order to get out, or 

 indeed until after it had given up the unavailing clawings, etc., 

 and stopped to rest. The association is formed in the same 

 way with such an "unlikely" or incongruous impulse as that 

 to scratch, or lick, or, in the case of chicks, to peck at the wing 

 to dress it. 



The examples chosen so far show the animal forming a sin- 

 gle association, but such may be combined into series. For 

 instance, a chick learns to get out of a pen by climbing up an 

 inclined plane. You then so arrange a second pen that the 

 chick can, say by walking up a slat and through a hole in the 

 wall, get from it into pen No. i. After a number of trials 

 the chick will, when put in pen No. 2, go at once to pen No. i 

 and thence out. You then arrange a third pen so that the 

 chick, by forming another association, can get from it to pen 

 No. 2, and so on. In such a series of associations the "act" 

 of one brings the animal into the "situation" of the next, 



