vii ASSIMILATION AND READJUSTMENT 123 



instances taken the results which go to modify the effects 

 of an excitement are in point of fact based on a second 

 quality of the same object which by its first perceived j 

 quality excites the reaction. Modifications of this type 

 are far more easily achieved than others by animals of low 

 intelligence. Thus, Professor Yerkes, testing frogs with 

 maze experiments, found that from 50 to 100 trials 

 were necessary to perfect the habit ; and in placing the 

 frogs in a box with a glass bottom, 20 to 30 experiments 

 did not suffice to teach them that the glass was to be 

 avoided. On the other hand Schaeffer's frogs learnt to 

 avoid disagreeable earthworms after a number of trials 

 varying usually from 2 to 7, and in at least one case 

 on the basis of a single experiment. 1 



These simple cases of Confirmation and Inhibition then 

 should apparently be grouped together as examples of a 

 specific and very primitive type of learning by experience. 

 The characteristic of this type is that the " experience " 

 which operates is an excitement resulting immediately from 

 the reaction of the organism to some prior excitement.! 

 Very often it arises from a second property of the object to j 

 which the first stimulus is due. This would for example 

 be true of the instances of tasting, burning, bruising, etc., 

 which we have used. But what seems essential is that 

 the result should follow immediately upon the first re- 

 action, and by a immediately " we mean closely enough 

 to impinge upon and so confirm or inhibit the conational 

 impulse by which that reaction is initiated and sustained. : 

 With this understanding we may briefly define this type| 

 of learning by experience as consisting in the modification 

 of the reaction to some stimulus through the immediate 

 effects of that reaction. The process is a case of that 

 which we have called Assimilation, because by its means 

 the excitement to which a stimulus gives rise is merged 

 in the consequential excitement and (at least for purposes 

 of guiding action) takes on its character. It is assimila- 

 tion in what is certainly one of its simplest forms. We 

 can see, however, that the process is closely analogous to 

 that of Selective Modification described above, and 



1 Schaeffer, loc. cit., pp. 324-25. 



