4 S JOSEPH U. YARB ROUGH 



here are probably more difficult than in learning the negative 

 response to pain. 



3. In most of the experiments reported the problem of suc- 

 cessive and simultaneous mode of presentation has been im- 

 portant. In these, successive presentation has been thought of 

 as immediate succession of the members of the stimuli. The re- 

 sults are divided as to the better mode of presentation, but the 

 majority of the data favor the simultaneous method. The writer 

 is of the opinion that the difference in results is best accounted 

 for by the difference in the material used in the several experi- 

 ments and difference in the method of procedure. 



The most important point of difference in method of pro- 

 cedure is the attempt to secure an exposure time in successive 

 presentation equal in length to that in simultaneous presentation. 

 If each member of the pair in the successive series is exposed 

 for the same length of time as the pair of simultaneous stimuli 

 the learning time is twice as long in the successive as in the 

 simultaneous presentation. Wohlgemuth felt a necessity for 

 making this exposure time equal in length if comparative data 

 were to be secured. To accomplish this he devised two methods : 

 i ) The exposure time for the simultaneous pair was made twice 

 as long as for each member of the successive pair, the number of 

 presentations remaining the same; 2) The exposure time re- 

 mained the same while the number of presentations were twice 

 as great in the simultaneous as in the successive pairs. Froeberg 

 objects to both of these methods. To the first his objection is 

 that it "implies that the strength of an association depends upon 

 the exposure time of the stimuli only, regardless of whether or 

 not the pair is exposed at the same time, and thus contradicts 

 the theory which was to be proved, namely that association takes 

 place only while the two experiences are present in conscious- 

 ness." Of the second method his statement is that "it disregards 

 the effect of the distribution of presentations." 



The criticism of the second method of equalizing the ex- 

 posure time is pertinent, but so much cannot be said for the 

 first. This first method is good or bad, depending upon which 



