RATE OF LEARNING IN THE WHITE RAT 49 



phase of the problem is under investigation. If the problem 

 attempts to determine the effect of the exposure time this is a 

 good method, but if the aim is to determine whether or not two 

 terms when presented simultaneously offer greater interference 

 to each other than when presented successively, thereby hin- 

 dering the process of learning, the method is inept. The method 

 used in our experiments and also by Froeberg is preferable in 

 such investigations. By means of it each term is exposed for an 

 equal time, regardless of the mode of presentation. In simul- 

 taneous presentation the exposure time of each of the two terms 

 is not only equal, but the presentations actually coincide in time. 

 In the successive mode the exposure time of each of the terms 

 is also equal, but the presentations succeed each other in time. 

 It is obvious that such a method reveals the relative value of the 

 two modes of presentation on the basis of term interference. 



Our data do not indicate term interference when the two terms 

 are presented simultaneously. On the other hand, they indicate 

 a more rapid learning with the simultaneous than with the suc- 

 cessive mode. These findings are in agreement with those of 

 Chamberlain, Bigham, Wohlgemuth, and Froeberg, when the 

 latter used nonsense syllables as material. 



As indicated above, the results have varied when different 

 materials were used. Disconnected words, associable words, 

 nonsense syllables, syllables, letters, colors, and diagrams have 

 served as materials for the experiments thus far reported in the 

 field of human psychology. From a study of all the results ob- 

 tained the following conclusion, reached by Froeberg, appears 

 to be true : If the material is such that the pair of stimuli form 

 an organic whole or can be attended as a unit, simultaneous 

 presentation is preferable; if it is such that the materials stand 

 as separate entities, or must be attended to separately in order to 

 be apprehended, successive presentation is preferable. 



In the field of Animal Psychology a certain motor response 

 and a definite external stimulus have served as the two terms to 

 be associated. After a motor response to one term is built up 

 the second term is presented in a certain temporal relation to 



