2 JOSEPH U. YARB ROUGH 



taneous association would have us believe that association can- 

 not be formed unless the facts or objects associated be ex- 

 perienced simultaneously. They recognize the fact that in every- 

 day life things are associated which succeed each other in time, 

 but they account for this on the assumption that "with the ces- 

 sation of the actual mental experience the nervous excitation is 

 not abruptly finished but continues, gradually dying away." 2 

 The second factor of the association, then, coincides in time with 

 this "gradually-dying-away" nervous excitation of the first, and 

 it is due to this simultaneity that the association of the two fac- 

 tors is formed. The rival theory of successive association, based 

 upon the hypothesis that the range of consciousness is not wide 

 enough to attend to two things at once, denies the possibility 

 of association between two factors simultaneously presented. 

 Those who hold this theory say that although the two factors are 

 apparently presented simultaneously they are in reality successive 

 experiences, since the attention is constantly vacillating between 

 the two. If successive association is correctly explained by the 

 simultaneity of the succeeding experience with the after-phase of 

 the preceding one, the data here presented show to a certain ex- 

 tent the duration of this "akoluthic" phase and its rate of dimi- 

 nution. 



Although our prime interest is in the first of the problems 

 listed above, it was found both practical and profitable to gather 

 data on the second and third. Very little work on the main 

 problem has been reported either in the field of animal or of 

 human psychology, hence it is on this point that these experi- 

 ments will probably have their greatest significance. The second, 

 likewise, has received scanty attention as yet. The third problem, 

 on the other hand, has been the subject of considerable experi- 

 mentation, although but little of this investigation has been in 

 the field of animal psychology. It is our purpose to present data 

 upon these timely problems, with especial emphasis upon the 

 question of the influence of the time interval in successive asso- 

 ciation upon the rate of learning in both its backward and its 

 forward directions. 



2 Semon, Richard, "Die Mnene," 2te Auflage, Leipzig, 1908. 



