70 BIOLOGICAL LECTURES. 



as shown in Fig. i, and put a chick, say six days old, in at A, 

 it is confronted by a situation which is, briefly, " the sense- 

 impression or feeling of the confining surfaces, an uncomfort- 

 able feeling due to the absence of other chicks and of food, and 

 perhaps the sense-impressions of the chirping of the chicks 

 outside." It reacts to this situation by running around, mak- 

 ing loud sounds, and jumping at the walls. When it jumps at 

 the walls, it has uncomfortable feelings of effort ; when it runs 

 to B, or C, or D, it has a continuation of the feelings of the sit- 

 uation just described ; when it runs to E, it gets out, feels the 

 pleasure of being with the other chicks, of the taste of food, of 

 being in its usual habitat. If from time to time you put it in 



Fig. I. 



again, you find that it jumps and runs to B, C, and D less and 

 less often, until finally its only act is to run to D, E, and out. 

 It has, to use technical psychological terms, formed an association 

 between the sense-impression or situation due to its presence at 

 A and the act of going to E. In common language it has learned 

 to go to E when put at A — has learned the way out. The 

 decrease in the useless runnings and jumping and standing still 

 finds a representative in the decreasing amount of time taken 

 by the chick to escape. The two chicks that formed this par- 

 ticular association, for example, averaged one about three and 

 the other about four minutes for their first five trials, but came 

 finally to escape invariably within five or six seconds. 



The following schemes represent the animal's behavior (i) 

 during an early trial and (2) after the association has been fully 

 formed — after it has learned perfectly the way out. 



