73 



to another. 



9. Tn the matter of elimination of errors, the outer 

 alleys are usually those in which useless movements are last 

 to drop out, but a 5-4-;.-2 order does not holl, i.e., errors 

 in 5 dro],ping out first, those in 4 second, etc. This bears 

 directly on the question of the relation of the food to the 

 learning process and seems to negate the pleasure-j^ain hyjo- 

 thfisls, but no conclusive evidence has been obtained. 



10 . The importance of an adequate test on retention is 

 made quite evident by these results. 



If an analogy may be drawn between the learning ability 

 of the rat and that of the human subject, it may be seen that 

 in general the old can lear i a given problem as well as the 

 young although more effort is required to do so. The efficien- 

 cy of this learning can only be measured by testing the reten- 

 tion ability. Should such tests show that the old animals 

 forget very rapidly and must relearn the problem continually 

 with little or no lessening of excess effort, comparing ujifavor- 

 ably vith the younger ones in these respect, the above conclu- 

 siont: would have to be modified. If, however, the limits of 

 retention in the groups are fou.id to be very nearly the same, 

 and the amount of effort necessary to relearn not greatly in- 

 creased for the older group over that for the younger, the de- 

 ductions would hold. 



