HABIT FORMATION IN THE ALBINO RAT 55 



this learning can only be measured by testing the retention 

 ability. Should such tests show that the old animals forget 

 very rapidly and must releam the problem continually with 

 little or no lessening of excess effort, comparing unfavorably 

 with the younger ones in these respects, the above conclusions 

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

 in the groups are found to be very nearly the same, and the 

 amount of effort necessary to releam not greatly increased 

 for the older group over that for the younger, the deductions 

 would hold. 



