Editorial. 133 



( Uniform (Reflex, Automatic, Habitual) 

 Simple Acts ■' Variable (Instinctive) 



( Unique (Voluntary) 



( Uniform (Habitual, Automatic) 

 Complex Acts < Variable (Habitual) 



( Unique (Voluntary) 

 Furthermore, it will be convenient for us to consider that 

 single uniform response to a simple external or internal stimu- 

 lus which is called a reflex as the unit of activity. Then, ac- 

 cording to the degree of variableness, the same relatively sim- 

 ple act may be classed as reflex, instinctive, or voluntary. The 

 frog when it responds to a touch near the nostril by raising its 

 fore leg as if to brush away the stimulating object, for all that 

 we can tell from a single reaction, may be reacting in any one 

 of the three ways. Only by careful observation of a series of reac- 

 tions to the same situation can that information which is neces- 

 sary for the classification of the act be obtained. If with each 

 repetition of the stimulus the same reaction occurs immediately 

 and with no perceivable variations, we class it as a reflex. If 

 the series presents acts which, although essentially the same, 

 vary slightly from one another, so that only the general form of 

 the reaction is predictable, we apply the term instinctive. And, 

 finally, if from time to time new acts appear in the series, so 

 that the reaction can never be predicted, the acts are voluntary. 

 As a usual thing, however, instinctive and voluntary actions are 

 more complex than reflexes, and analytic study reveals that 

 they are really made up of a number of simple reflexes closely 

 associated. It was the discovery of this that led Loeb' to speak 

 of the instinctive act as a chain-reflex. 



Possibly it is worth while to present an illustration of these 

 types of action and their differences as exhibited by the frog. 

 Suppose the conditions of reaction to be the following. To 

 the stimulus of a touch on the nose the animal reacts by, i) a 

 leg movement, or 2) ahead movement, or 3) locomotion, or 4) a 

 combination of the three. Then, according to the degree of 

 variableness of the reaction series, the reaction would be class- 

 ed as: 



'Comparative Physiology of the Brain and Comparative Psychology, p. 178. 



