126 PsYCHOBIOLOGY 



way. The development or modification of perception is the develop- 

 ment or modification of the reaction-habit, in accordance with the general 

 principle of drainage, and the empirically ascertainable laws of habit. 

 If the reaction to the object is modified, the perception is modified ipso 

 facto. Such modification (whether developmental or destructive) of the 

 perceptual reflex may take place in relative independence of the thought 

 processes : but normally, as stated above, the modification of each influences 

 the other. 



CIRCULAR REFLEXES. 



The three types of inter-muscular reflexes are : ( 1 ) reflexes from a cer- 

 tain group of muscles to an entirely different group; (2) reflexes back to 

 the same group, resulting in a new combination of contractions — a new 

 "muscle pattern"; (3) reflexes back to the same group and giving the 

 same combination of contractions. There are also reflexes which lie 

 intermediate between the first and second and, between the second and 

 third types. 



The first reflex-type is illustrated by the reflex from the muscular 

 stimulation of pronouncing the word " throw " to the muscular activity 

 of throwing ; the second type is that of the oral repetition of a memorized 

 series of words ; and the third type is most strikingly illustrated by the 

 " stuttering " of certain stammerers. 



In stuttering, the reflex discharge from the muscular stimulation of 

 enunciating a certain syllable, instead of being directed to the production 

 of the new muscle-pattern required by the next syllable, are directed in 

 the same way in which the preceding discharge was sent, thus resulting 

 in a repetition of the same syllable. The immediate cause of this in- 

 efficient functioning is not known, but various contributing causes have 

 been suggested. 



Circular reactions are not exclusively pathological. An important fea- 

 ture of the learning process is the circular reaction by which a newly 

 acquired reaction is repeated several times. Such repetition is especially 

 characteristic of reactions which are accompanied by pleasure. In such 

 reactions an important feature of the afferent current (probably from the 

 viscera and somatic sources) is that the efferent discharge tends to 

 occur over the same routes and in the same way as the preceding dis- 

 charge which gave rise to the pleasure. 



The habit-forming function of pleasure is not limited to the cases in 

 which the act is circularly repeated in serial fashion. The circular re- 

 inforcement seems to occur even in cases where the act occurs but once, 



