A SIMPLE MAZE 363 



greater retardation shown by the other groups (in excess of 53 

 per cent) is due, almost certainly, to this one factor of summation 

 of instinctive reactions. 



III. THE BEARING OF THE RESULTS UPON THEORIES OF THE 

 NEUROLOGICAL BASIS OF LEARNING 



Experimental work upon the effects of the distribution of effort 

 in learning has given uniform results for practically every proc- 

 ess studied. Within limits as yet undetermined concentrated 

 practice is less efficient than distributed. But no satisfactory 

 explanation of this seemingly universal phenomenon has yet been 

 advanced. In an earlier paper (Lashley, '15) I have listed seven 

 different possible explanations for the superiority of distributed 

 practice found in archery, between which it is not possible to 

 choose on the basis of the existing evidence, and the list then 

 given was certainly not exhaustive. 



The universality of the phenomenon might be taken to indicate 

 that it is due to some fundamental process in the formation of 

 new functional connections in the nervous system and this is the 

 view which seems to be most generally held. For example, 

 Starch says ('12) : "Why are shorter and more numerous periods 

 economical? The main reason, no doubt, is the well known fact 

 that a period of rest after newly formed associations gives them 

 a chance to become settled and fixed." Colvin ('11) makes much 

 of this hypothesis, also, and gives it the rank of a general law 

 that "it takes a certain amount of time for associations to fix 

 themselves," and this is used to explain not only the effects of 

 distribution of practice but also retroactive inhibition and the 

 facts included under Jost's law. 



From the standpoint of neurological theory the truth or falsity 

 of this hypothesis is of extreme importance. If there is a gradual 

 strengthening of associations during periods of non-practice there 

 is implied a continuation of chemical changes within the nerve 

 cells, initiated by the passage of a neural impulse through new 

 channels and persisting for hours or even days without the in- 

 fluence of continued impulses. If, on the contrary, no such 



