DISTRIBUTION OF EFFORT IN LEARNING IN WHITE RAT 43 



III RETENTION 



Very little has been said about the factor of retention in the 

 rats for the reason that prior to any analysis of the results so 

 far obtained, it seems desirable to consider the factors that 

 determine retention. These are of two kinds: those that are 

 dependent on the general condition of the organism and those 

 that arise from usual extraneous disturbances. The first of 

 these factors is connected with the problem of general metabolism. 

 The important one, the control of diet with exercise, during the 

 interval of the last trial and the first retention test, need only 

 be mentioned. There is great danger at this time of overfeeding 

 and thus defeating the results obtained by an increase in weight 

 and the evils arising therefrom. In order to keep down body 

 weight, daily exercise is in a measure effective and can be easily 

 instituted, but some difficulty in regulating food is often encoun- 

 tered, one animal may gain fat rapidly on an amount of food 

 that would not be at all sufficient for another. To maintain 

 the proper bodily tone necessar}^ to produce active organisms is 

 of the first importance in retention tests. 



Among the second class of factors, extraneous disturbances, 

 may be noted those arising from accidental noises, bites of 

 parasites, unusual olfactory stimulation, etc. These disturb- 

 ances are of the same kind as those met with in the learning 

 process. For some reason, however, the animals during reten- 

 tion tests seem to be more sensitive to such disturbing stimuli 

 than they are during the learning process. Why this should 

 be so seems hard to answer. 



Whatever the cause of such disturbances the fact remains 

 that it is difficult to state by observing the amount of time the 

 first retention test requires just what proportion of the excess 

 time must be assigned to actual loss through disuse and what 

 to disturbing factors. 



But in some cases a loss in retention was unmistakable, and 

 was often noticed in particularly interesting points in the solu- 

 tion of the problems. In all three problems experimented with 

 the rats showed evident loss in retention by wandering about 

 aimlessly for a time, then suddenly and unexpectedly attacking 

 the problems. Hesitations were frequent. In the latch box 

 they were often noticed in the many positions the rats took 

 before making an immediate movement to lift the latch. Some 



