RATE OF LEARNING IN THE WHITE RAT 5 



immediate written reproduction again tested the amount memo- 

 rized. For the three intervals the average percentages of error 

 were, respectively, 51.12, 36.52, and 23.9 for the word lists, and 

 44.09, 52.65, and 38.44 for the letter lists. In both, the amount 

 learned increased with the lengthening of the interval. Berg- 

 strom concludes : "The effect of increasing the interval is greatly 

 to decrease the number of errors. . . . Indications are that an 

 interval longer than any employed would have still further re- 

 duced the errors." 



Wohlgemuth 5 (1914) reports an experiment the purpose of 

 which, as he states it, is i) "to decide by experiment, if possible, 

 between the claims of the rival theories of Simultaneous and 

 Successive Association," and 2) "to investigate the influence of 

 the closeness of connection between the members presented simul- 

 taneously." He used eight subjects, whose age and qualifica- 

 tions were undefined. To them he gave a series of tests con- 

 sisting of pairs composed of a colored field (cardboard) fol- 

 lowed by a black shape mounted on a white ground, or vice- 

 versa. The exposure was timed by a Miiller memory apparatus, 

 a certain definite period of exposure thus being given each card. 

 Obviously, under such conditions the simultaneous pair would 

 have just the same period of exposure as each member of the 

 successive pair. He found the successive mode of presentation 

 superior to the simultaneous, but accounted for the difference 

 on the basis of the unequal exposure time for each pair of stimuli. 

 To overcome this defect two groups were formed: in the first, 

 only half the number of exposures was given in the successive 

 series, while each member of the pair was exposed for the same 

 length of time as the pair of simultaneous stimuli i.e., the rate 

 of the memory apparatus remained the same; in the second, the 

 same number of exposures was given in both series and the same 

 time given each pair, but only half time was given each member 

 of the successive pairs i.e., the apparatus was set to work twice 

 as rapidly in the successive series as in the simultaneous. Wohl- 

 gemuth finds that in the first group the average scores were 35.5 



5 Wohlgemuth, A, "Simultaneous and Successive Association," British 

 Journ. of Psychol., VII, 1914-15, pp. 434-452. 



