Literary Notices. xlv 



great importance for the quality and quantity of work they can do, 

 this does not conform to any general type, and is, therefore, not an 

 inherited modification of the nervous system. The daily rhythm is the 

 result of a number of stimulating and depressing causes, whose influ- 

 ence habit tends to fix upon the system. These very suggestive 

 observations are followed by a critical discussion of fatigue. 



Part n deals with the retardation of memory by means of the 

 interference of associations and continues some observations reported 

 in the American Journal of Psychology, Vol. V, No. 3. Two packs of 

 cards with the same words or symbols were sorted successively into 

 different positions. On the average 65 seconds were required for the 

 first pack, but 85 for the second, if this was sorted immediately after- 

 wards. The difference is called the interference time since it is due 

 to conflict of associations and not to fatigue. The time for sorting 

 the cards decreased considerably with practice, but the amount of 

 interference did not. The latter however decreased as the interval 

 between the two acts was increased, at first very rapidly, then more 

 slowly. 



These tables of observations suggest several important pedagogi- 

 cal hints in the training of the memory and serve to explain many 

 cases in which errors of computation, translation, etc. may remain 

 unperceived even after hours of search, but which may flash into the 

 mind in a moment after a few hours of rest. The author concludes: 

 "As a class, these facts have usually been explained by some theory 

 of unconscious cerebration, or they have been attributed to the sum- 

 mation of stimuli, or to rest. 



" That these phenomena are due to a summation of stimuli which 

 gradually gathers sufficient strength to break through the nervous re- 

 sistance into the correct association, seems impossible, since every 

 nervous excitement diminishes in intensity if left to itself, and the 

 quickest and most striking results are usually obtained by putting the 

 problem entirely out of mind for a while. 



"Fatigue and rest have, as is well known, a considerable influ- 

 ence upon the rate of mental work, but these cases seem to occur, 

 just as in the memory work, when there is no fatigue present. The 

 unreliable and often fantastic character of mental processes in the in- 

 direct field of consciousness, in revery, and in dreams, the stupidity 

 of secondary consciousness together with the absence of fatigue from 

 this imagined unconscious cerebration, makes it probable that it is of 

 little importance, and that conscious attention is the forge in which 

 most, if not all, valuable mental work is done. ... ..." 



