57 



in the formation of habits in which the factor of speed is of 

 an importance equal to or greater than that of exactuess, the 

 older animals would be considerably handicajped. In the field 

 of ani:T^al experimentation illustrations of habits where speed 

 is an important factor are difficult to find. On the human 

 side such an illustration might be had in the acquiring of tech- 

 nique in piano playing or voice culture, either of which de- 

 mands the rapid succession of the muscular activities involved 

 in rendering scales, arpeggios, trills, etc. It would seem that 

 habits requiring extreme rapidity of excession within a jre- ^ 

 scribed rthym could not be learned by the older animals. 



A comparison of the relation of distance to time in the 

 younger and older groups is interesting. In the first two 

 groui 8 the distance is relatively high showing the excess ac- 

 tivity displayed by the younger animals, in the 200-day group 

 it is about the same as the time, indicating that excess activ- 

 ity is at a minimum, while in the last group it is much less 

 than the time, showing that the effects of old age have begun 

 to manifest themselves through a general slowing up of activity. 



If the distance alone be taken as a measure of activity, 

 our results agree with those of Slonaker who found the most ac- 

 tive age to be between ten and twelve and a half months, since 

 our 300-day rats covered more distance in learning the problem 

 than any other group. If, however, distance be considered in 

 relation to time, the older rats a] pear much less active t}ian 

 the younger ones, as is shown by the average high speed attain- 



