Differences in Behavior 269 



Another indication of individual initiative in action ap- 

 peared in the tendency of certain mice to climb out of the 

 experiment boxes or labyrinths. It would have been ex- 

 tremely easy for any of the mice to escape from the labyrinths 

 by scaling the walls of the alleys, for they were only 10 cm. 

 in height, and when a dancer stood on its hind legs it could 

 easily reach the top with its nose. But, strange though it 

 will seem to any one who has not worked with the dancer, 

 not more than one in ten of the animals which I observed 

 made any attempt to escape in this manner. They lacked 

 initiative. That it was not due to a lack of the power to 

 climb, I abundantly demonstrated by teaching a few individ- 

 uals that a scramble in one corner meant easy escape from 

 the maze of paths. I do not think any one of the mice was 

 physically incapable of climbing, but I am confident that they 

 differed markedly, not only in the willingness to try new modes 

 of action, but in the readiness with which they could climb. 

 I have already said that individuals differ noticeably in the 

 scope of their activity. By this statement I mean that they 

 try a varying number of kinds of activity. As in the case 

 of men, so in mice, one individual will do a greater number 

 of things in a few hours than another will in weeks or months. 

 The dancers differ in versatility, in individual initiative, as 

 do we, albeit not so markedly. 



Important differences which may with certainty be de- 

 scribed as age differences are not so obvious as are such marks 

 of individuality as have been set forth in the preceding pages. 

 I have noted few changes in discriminative sensitiveness, 

 other than those with regard to auditory sensitiveness, which 

 could be correlated with age. In certain instances adults 

 appeared to be able to discriminate more accurately and more 

 easily than young mice, but it is difficult to say whether this 

 change belongs under sensitiveness or docility. I have not 



