12 JOSEPH U. Y ARE ROUGH 



having learned it in the forward direction. These data are not 

 considered conclusive, for all who have trained rats know that 

 considerable retracing is done while mastering a maze. 



Summary, i) The majority of the experimental data re- 

 viewed favors the simultaneous mode of presentation. 2) In 

 regard to the time interval, Bergstrom is convinced that with the 

 increase in the length of the unfilled time interval the amount 

 learned increases. Froeberg is of the opinion that an increase in 

 the length of the time interval increases the difficulty. 3) All 

 investigators have found a tendency toward backward association 

 a tendency varying in strength, but seldom equal to and never 

 stronger than the forward tendency. 



