FACTORS IN LEARNING BY WHITE RATS 345 



alley over that of entering it (i.e., the practice-effect according 

 to the law of frequency) is proportionately greatest for the 

 cut de sac nearest the food box, and that it steadily decreases 

 in order back to the first cul de sac. This would mean, on the 

 basis of pure frequency factors in learning, that in general the 

 nearest blind alley to the food box would be eliminated first, 

 the second next, and so on. Elimination of all entrances to the 

 last cut de sac— that nearest the food box — would then convert 

 the maze in question for the given rat into a nine-blind-alley 

 maze, elimination of the ninth cut de sac would make practically 

 an eight-blind-alley maze, and so on, till the maze habit became 

 perfectly established. 



This would explain perfectly, then, a backward elimination 

 of cul de sacs without any suppositions of " retroactive associa- 

 tion," or of stamping-in effects of pleasure from eating the 

 food, the effects varying inversely with the nearness of the 

 pleasure. Since, however, the rat is not obliged to continue 

 each return run to the starting place, and often does not do 

 this, the mathematics of the above calculation is indefinitely 

 complicated. We could go ahead and determine the proba- 

 bility of such complete returns from the second, from the third, 

 from the fourth, etc., blind alleys; but such calculations would 

 add nothing of further advantage to the theory we are testing. 

 It is very certain, moreover, that the animal very early in the 

 learning process eliminates most of the return movements. 6 In 

 general, the following statement will suffice, and it finds support 

 not only in theoretical determinations but also in results ob- 

 tained by flipping coins as shown in the four illustrative trials 

 tabulated in Table I: The greatest number of entrances to 

 blind alleys occur in the part of the maze first to be passed 

 through. This is because every animal reaching the starting 

 place on a return must reverse its direction, while the contrary 

 is true at the other end of the maze. Rats entering the food 

 box cannot return into the maze. If the maze is one having 

 many blind alleys, however, the animals may make compara- 

 tively many entrances also to cul de sacs in about the middle 

 of the maze, so far as mere probability is concerned, for the 

 chances of complete returns from distant parts of the maze 



6 Peterson, Jos. The Effect of Length of Blind Alleys on Maze Learning: An 

 Experiment on Twenty-four White Rats. Behav. Mon., Ser. No. 15, 1917. 24 ff. 



