Eeceptoes, Neurons, and Effectors 125 



processes ; in particular, activity of the vocal organs tends to occur. It 

 is a significant fact that everything we "think of" has a vocal sign: a 

 combination of muscular movements distinct from every other such com- 

 bination. But it is not probable that in the normal adult the vocal move- 

 ments, or other movements, actually occur to the extent this theory would 

 seem to indicate. The fact is that the muscular activities are necessary 

 and effectual in forming the associations, but as the habit becomes firmly 

 fixed, the importance of the muscular movements diminish, and they 

 tend to be eliminated. 



It is apparent, therefore, that in some way, the reflexes are short- 

 circuited, i. e., that the efferent current eventually starts an afferent 

 current without descending to the muscle level. This is especially im- 

 portant in serial activities where the ideational factor is less important 

 or practically eliminated, as for example, in performing a series of rapid 

 movements on the typewriter. In the series of seven acts required to 

 write the word " without ", it would decrease efficiency, if the initiation 

 of each succeeding act were consequent upon the completion of the 

 preceding act. Such linkage is typical of the learner or the less prac- 

 ticed typist. After the proper habit is formed, each successive act in 

 writing stock words are initiated before the completion of the preceding 

 act. The comparison of such habits with ideational association suggests 

 to us that the short-circuiting mechanism is in the cerebellum ; but this 

 is for the present merely a plausible conjecture. 



Somewhere in its efferent path, the reflex-current divides and one branch 

 reaches a mechanism — a mechanism in close functional relation with the 

 entire striped muscular system — in which the proper return afferent cur- 

 rent is initiated before the effectors have finished their action, or even 

 (in the case of thought process), when the action of the effectors is 

 negligible. This is the ideal of practical habits of the serial sort, and 

 of course is realized only intermittently. In many cases, and in the learn- 

 ing process always, the intervention of the muscular process occurs. 



PERCEPTUAL HABITS. 



The serial linkage of reflexes is but one phase of habit formation. An 

 equally important phase is the modification of the individual reactions 

 themselves. This is equally important for the development of action as 

 such and for the development of perception. The pyschology founded on 

 Locke has described the development of perception as the addition of 

 thought or imagination to elementary perception. Although the develop- 

 ment of thought-process and the development of perceptual process mutu- 

 ally modify each other, it is no longer permissible to confuse them in this 



